RadialTruckTire AndRetread ServiceManual CONTENTS Section Title Page Section Title Page 1. Radial Truck Tire Terms 5 8. Ride Disturbance 58 Cross-Sectional View of Typical Tire 6 Ride Test Tips 60 2. Tire Selection 8 Ride Diagnostics: Tires/Wheels 60 Tire Selection Process 9 Balance Related Vibration 60 Tire Selection Process Work Sheet 16 Run-Out Related Vibration 60 Mesuring Radial Run-Out 61 3. Mounting Procedure 19 Safety Instructions 20 9. Factors Affecting Truck Fuel Economy 63 Wheel Inspection Guidelines 20 Vehicle and Engine Design 64 Lubrication 20 Vehicle Operation 67 Tire and Rim Cleaning 21 Tire Selection and Maintenance 70 Tubes and Flaps 22 Environmental Conditions 74 Assembly of Tire Tube Flap 22 Tire Description & Specifications 76 Tubeless Tire Mounting 23 Summary 77 Installation 23 Appendix 78 Demounting 24 10. Tire Repairs 80 Matching of Duals 25 Nail Hole Repair Procedures 82 Spacing of Duals 26 Section Repair Limits in Spacers 26 Sidewall and Shoulder Area 84 Proper Matching of Rim Parts 27 Application of Center-Over-Injury Safety Precautions 28 Section Repairs 85 Mounting and Inflation 29 Radial Ply Tires 85 Operation 31 Crown Repair Limits 85 Servicing Tire and Rim 31 11. Retreading 86 Inspection Procedures 31 Introduction 87 4. Collecting and Storing Tire Information 34 Planning A Retread Plant Visit 87 Branding Tires 35 Plant Inspection 87 Radio Frequency Identification Tags 36 Definitions 90 RF Tag Usage 36 Retread Plant Inspection Checklist 92 5. Inflation 37 12. Miscellaneous 94 Underinflation 40 Use of Chains on Radial Truck Tires 95 Do’s and Don’ts for Maintaining Proper Tire Siping Inflation Pressure 42 95 Nitrogen Inflation 42 Dynamometer Tests 96 Mixing Radial and Bias Ply Tires 96 6. Total Vehicle Alignment 43 Noise 97 Steer Axle Alignment 45 Tire Storage Recommendations 99 Loaded vs. Unloaded Alignment Settings 45 When Does The Warranty End? 100 Toe 46 Tire Sealants And Balance Materials 100 Camber 46 Caster 46 13. Standards and Regulations 101 Ackerman Steering Effect on Tire Wear 47 Federal Motor Vehicle Safety Standards Drive Axle Alignment 48 Testing and Certification 102 Trailer Axle Alignment 49 Federal Motor Carrier Safety Regulations 102 In-Service Alignment Recommendations 49 Inspection 103 Minimum Tread Depths 104 7. Factors Affecting Treadwear 50 Commercial Vehicle Safety Alliance (CVSA) 104 Steer Tire Wear 52 Regrooving/Tire Siping 105 Setback Steer Axles 53 Drive Tires 54 Load Ratings and Inflation Data 107 Bearing Adjustment 55 Truck Type and Weight Class 108 Environmental Effects 56 Index 109 How Speed Affects Tire Wear 57 Forward

This manual was prepared as a guide to the selection, operation, and maintenance of Goodyear radial truck tires. The subjects covered are all essential to good tire performance. Detailed explanations on selection, mounting, air pressure, vehicle alignment, and other important issues are supported by illustrations for clarity. Use this manual often as a reference. It will help you get extended fuel economy, treadwear, and casing life from your Goodyear radial tires. Radial Truck Tire S ECTION O NE Nomenclature

Radial Truck Tire Terms

5 Radial Truck Tire Nomenclature S ECTION O NE

I Tread 1. 2. Crown Shoulder 3. Tread Skirt H. Belts

G. Radial Ply

4. F. Sidewall Unisteel Sidewall Radial

A. Liner

E. Apexes

5. Stabilizer Ply D. GG Ring C. Chafer 6. Bead Heel B. Bead Core 7. Bead Toe

Tire Components Tire Areas A. Liner — A layer or layers of F. Sidewall — The sidewall rubber must 1. Crown — Area of the tire that rubber in tubeless tires that resists withstand flexing and weathering and contacts the road surface. air diffusion. The liner in the tubeless provide protection for the ply. 2. Shoulder — Transition area between tire replaces the innertube of the G. Radial Ply — The radial ply, together the crown and tread skirt. tube-type tire. with the belt plies, withstands the loads 3. Tread Skirt — Intersection of tread B. Bead Core — Made of a continuous of the tire under operating pressure. and sidewall. high-tensile wire wound to form a The plies must transmit all load, driving, high-strength unit. The bead core is the braking and steering forces between the 4. Sidewall — Area from top of bead to major structural element in the plane of wheel and the tire tread. the bottom of the tread skirt. tire rotation and maintains the required H. Belts — Steel cord belt plies provide 5. Stabilizer Ply — A ply laid over the tire diameter on the rim. strength, stabilize the tread, and protect radial ply turnup outside of the bead and C. Chafer — A layer of hard rubber that the air chamber from punctures. under the rubber chafer that reinforces resists rim chafing. and stabilizes the bead-to-sidewall I. Tread — This rubber provides the transition zone. D. GG Ring — Used as reference for interface between the tire and the road. proper seating of bead area on rim. Its primary purpose is to provide traction 6. Bead Heel — Area of bead that and wear. contacts the rim flange, the “sealing E. Apexes — Rubber pieces with point” of the tire/rim. selected characteristics used to fill in the bead and lower sidewall area and 7. Bead Toe — The inner end of the provide smooth transition from the bead area. stiff bead area to the flexible sidewall.

6 Radial Truck Tire S ECTION O NE Nomenclature

• Aspect Ratio (AR) — The section Section height divided by the section width, Width (SW) expressed as a percentage (SH/SW x 100 percent). • Loaded Section (LS) — The width of the cross section at the Tire and Outside Rim Association’s dual tire load and Section Diameter inflation pressure. Height (SH) (OD) • Static Loaded Radius (SLR) — The distance from the road surface to the horizontal centerline of the wheel, under dual load. Rim • Minimum Dual Spacing — The Flange Width minimum dimension recommended Height from rim centerline to rim centerline for optimum performance of a dual wheel installation.

Minimum Dual Static Loaded The Tire & Rim Spacing Radius (SLR) Association Yearbook The Tire & Rim Association Yearbook provides essential information for the interchangeability of tire, wheel and rim products for cars, trucks, buses, cycles, Loaded Section off-the-road, agricultural (LS) and industrial vehicles. To obtain a copy, write or call: The Tire & Rim Association, Inc. 175 Montrose West Ave. Definition Suite 150 • Footprint — The surface of the tire in • Net/Gross Ratio — Tread pattern Copley, OH 44321 contact with the road surface at any contact area to total tread area. 330-666-8121 given load and inflation pressure. www.us-tra.org • Outside Diameter (OD) — • Tread Width — Distance across The unloaded diameter of the tire/ tread surface. rim combination. • Non-Skid — Tread depth from tread • Section Width (SW) — The maximum surface to bottom of major grooves. width of the tire section, excluding any lettering or decoration. • Undertread — Gauge of rubber between top of belt package and • Section Height (SH) — The distance bottom of grooves. from the rim to the maximum height of the tire at the centerline. • Turn Radius — Curvature of the tread face from shoulder to shoulder.

7 Tire Selection S ECTION T WO

Tire Selection

Selecting the proper tire size, load range and

design is very important to insure satisfactory

performance. The best guide is to follow

past experience and use the advice of

professionals who are familiar with the types

of tires used in service conditions similar to

yours. Goodyear representatives are trained

to aid you in this important decision. The

following will provide basic guidelines for

proper tire selection.

*Information courtesy of The Maintenance Council (TMC)

— Recommended Practices Book

8 S ECTION T WO Tire Selection

TIRE SELECTION PROCESS Purpose Introduction the gear ratio. Some change may require This Recommended Practice is The process of determining which a different rim (width, pressure limits). intended to make the tire purchaser, fleet tire to select for a particular job or Tire Clearances — In order to select operator, or maintenance manager aware operation may sometimes seem difficult a new tire size for a given application, of major items for consideration, and to or complex. Indeed, the proper selection the dimensional clearance of the tire provide a step-by-step thought process involves a myriad of decisions concerning must be acceptable. The following for selecting the best type of tire for the the size, the type, and the tread design define those areas that must be checked: application. The following sections of the tire based upon the intended 1. Vertical Clearance is the distance provide a brief explanation of the various application. Other considerations are between the top of the tire tread tire selection criteria that must be the manufacturer of the tire, the tire and the vehicle immediately above addressed. A summary of considerations dealer, price, availability, and the warranty it. This clearance varies as the axles is also listed to enable the decision-maker coverage which comes with the product. operate. The vertical movements to identify advantages and disadvantages However, there is a logical method for of the whole axle in relation to the of each of the selection criterion. selecting which kind of tire would be chassis are normally limited by an If higher steer tire pressures are most appropriate depending upon an axle stop. To determine vertical required, this may mean you’ll be using assessment of the many considerations clearance, subtract the axle stop different inflation pressures for drive and surrounding the fleet operation. clearance from the total clearance trailer tires. Be aware that all tire use selections above the tire at rest. While the considerations may not will have advantages and disadvantages be all-encompassing, they point out the depending upon vehicle design and 2. Front Tire Clearances are the distances major issues that should be dealt with vocation. Make certain your choices are between the front tires (on both before selecting a tire. Because of the in line with your perceived fleet needs steering lock positions) and the pace of technology change in the tire and contact your tire suppliers for expert vehicle. Clearances of front wheels industry, certain considerations may assistance in making your selection. must be checked by turning the wheels become less important while new ones from full left lock to full right lock, may arise from time to time. Tire Clearance Restrictions since the minimum clearance might occur at some intermediate point. New Equipment — When spec’ing a new vehicle, the prospective owner can 3. Overall Width — When fitting larger be quite imaginative in creating a vehicle or wider tires to an existing vehicle, that meets specific needs. Tires, however, the overall width across the dual tires may be the limiting factor to this creativity is increased by half of the increase in since they must be capable of carrying the section width of each outside tire the expected load and be made to certain and the increase in offset of each minimum dimensions. The fleet owner outside wheel. The overall width can choose from several types of tires that across the tires is measured at the can carry the anticipated load, but may twelve o’clock position and not at the be forced to redesign a vehicle’s overall lower side (six o’clock position) dimensions if the tires that can carry the where the tires deflect due to load. load are larger than originally desired. When using tire chains, a minimum Existing Equipment — When changing of two inches more clearance is needed the type or size of tires used on existing to provide clearance between the equipment, space restrictions are more dual assembly. inflexible. Not only must a tire be selected that can carry the load, it must fit in an existing space. In addition, when changing tire sizes on an existing power unit, consideration must be given to the effects the new size tire will have on

9 Tire Selection S ECTION T WO

Rims And Wheels Radial and Bias Tire typically made with one steel body The selection of rims or disc wheels Construction ply or multiple body plies of other materials. Under the tread area, the goes hand-in-hand with the selection of There are two basic types of tire tires. When ordering new equipment, radial tire usually has three or four construction — radial and bias — that crossed plies or belts made of steel cord specifying the recommended rim for the must be considered when choosing either tire size selected will ensure optimum to stabilize the crown area and offer a replacement tire for certain applications better puncture resistance. The radial performance. or when spec’ing new tires on an original Rims are identified by a diameter and sidewall area is generally less stiff than equipment vehicle Figure 2.1. the bias ply sidewall, though the tread width and, in the case of tube-type rims, Bias ply tires are constructed of also with a type code. The type code area is normally much stiffer. overlapping crossed layers of cord Bias ply tires have been designed over designations are used on tube-type material and are typically made with products to help identify rings and rims the years to perform in many different nylon, polyester, or other materials. types of applications from all-highway for interchangeability. For example, The crossed plies run on a diagonal from a 20 x 7.5 FL rim would have a nominal to on-off road, to all off-road service tire bead to tire bead and comprise a conditions. With the advent of the radial diameter of 20 inches; a width between generally stiff sidewall area. Sometimes, the flanges of approximately 7.5 inches; tire and some of its inherent advantages, extra crossed plies or breakers are used the bias tire is now used much less and be a FL type rim. Other typical under the tread area to further stiffen type codes are: CR, 5˚, LB, and LW. It is frequently in long haul over-the-road the crown area and provide better applications. Radial tires typically are important that the rim size be approved wear resistance or other performance for the tire being used. This assures proper used in applications where heat build-up parameters (such as puncture with bias ply tires is a problem. With fit and performance of the tire and rim. resistance, etc.). The tire or rim/wheel manufacturer’s data the many improvements to radial tire Radial ply tires are made with the construction made in recent years, the book or Tire & Rim Association Yearbook (or cord material running in a radial or equivalent), and www.goodyear.com/truck radial tire is now used in virtually all direct line from bead (at 90 degrees types of service conditions. specify approved rims for each tire size. to the centerline of the tire), and are When selecting the correct wheel or rim type, it is important to determine the operating conditions to which the wheel or rim will be subjected. Conditions to consider are loads, speeds, road surfaces, use of bias or radial tires, tire pressure, tire size, and the use of tube-type or tubeless tires. Caution is necessary in selecting wheel/rim offsets to ensure proper tire spacing, body and chassis clearance, and overall track width. If dual tires are used, dual spacing and tire clearance must be considered. Take precautions to ensure that the rim and wheel not only have the approved contour, but also have the load and inflation ratings sufficient for the tire in the intended application. For more detail in selecting the correct wheel/rim, refer to TMC RP211A, Radial Bias Rim and Wheel Selection and Maintenance.

Figure 2.1

10 S ECTION T WO Tire Selection

Bias Ply Tire Considerations TABLE 1 • stiffer sidewalls give better driver handling/feel Conventional vs. Low Profile Tire Comparison • lower susceptibility to sidewall 11R22.5 295/75R22.5 snags/hazards/rusting • lower initial tire purchase price (Low Profile) Radial Tire Considerations Diameter 41.5'' 40.0'' • better treadwear performance Section Width 11.0'' 11.2'' •higher potential for retreading Nonskid 19/32'' 18/32'' • more fuel efficient Rim 8.25'' 8.25'' • lower susceptibility to tread punctures SLR 19.4'' 18.7'' • better traction characteristics RPM 501 514 Tubeless And Table 1 Tube-Type Tires Low Profile Tires Drivetrain/gearing must be taken into The tubeless tire is similar in Low aspect ratio tires are a category account when converting to low profile construction to a tube-type tire, except of radial tubeless tires which feature tires, either at the original equipment or that a thin layer of air and moisture- section widths wider than their section replacement level. These involve engine resistant rubber is used on the inside of height. The ratio of tire section height RPM, transmission, drive axle gear ratio, the tubeless tire from bead to bead to to section width for these low aspect and tire RPM. The objective is to obtain obtain an internal seal of the casing. This ratio tires generally fall between 80% the most fuel efficient engine RPM/ eliminates the need for a tube and flap. to 70%. ground speed relationship consistent The two types of tires require different Low aspect ratio tires have shorter with service condition requirements. rim configurations: the tubeless tire uses sidewall heights and wider tread widths The effect on road speed at the same a single-piece wheel; and the tube-type than their “conventional” aspect ratio engine RPM using a 55 mph base depends tire requires a multi-piece wheel assembly tire counterparts. upon which conventional aspect ratio Figure 2.2. Both tires, in equivalent sizes, These differences lead to the and low profile tires are involved. can carry the same load at the same following tire characteristics: Generally, if the percent change in the inflation pressure. However, tubeless • improved treadwear (less irregular tire RPM is 3% or less, a gearing change tires generally offer more benefits than wear) on steer and trail axles is not required Table 1. tube-type tires in line-haul operations. • lighter weight and less federal excise tax Tubeless Tire Characteristics • better trailer cube potential due to Wide-Base vs. Tube-type: smaller tire diameter on new equipment (Super Single) Tires • less complicated mounting process due • improved stability and handling from to use of a single-piece wheel higher lateral spring rate A wide-base tire is simply a larger tire • decreased weight with lighter tire/ •greater susceptibility to sidewall with a lower profile by nature. Currently, wheel assembly curb damage the primary application in North America • less maintenance of parts and reduced As fleet experience with low profile is on vehicles whose front axle loads exceed parts inventory tires increases, other considerations the capacity of standard tires. Construction • improved bead durability potential (such as vehicle geometry, alignment vehicles such as cement mixers and refuse from less brake drum heat resulting maintenance, and brake wear) may haulers are prime examples. In addition from higher wheel clearance need to be addressed depending on the to increased load capacity, these larger • improved crown and sidewall durability applications and service requirements tires provide improved flotation versus potential from cooler running of the operation. conventional size tires. tubeless casing The common wide-base sizes include: • better lateral stability from lower 385/65R22.5, 425/65R22.5, 445/65R22.5, section height 435/50R22.5, and 445/50R22.5. •reduced downtime from punctures

11 Tire Selection S ECTION T WO

The pros and cons of wide base take full advantage of the wide base change in the tire RPM is 3 percent or singles versus duals in many performance single concept is to use a 77.5 inch wide less, a gearing change is not required. categories are dependent on specific axle in place of the standard 71.5 inch. In a tire selection process, it is vehicle configuration and operations. Inherent advantages of duals versus mandatory that consideration be given Some key considerations and potential wide base singles include standardization to selecting a tire size and load range benefits are discussed in the following of tires/wheels, reduced road service due which at least equals the maximum load paragraphs. to tire problems through “limp” capability requirements by axle position (steer, Potential advantages for wide base to get to repair facility, and improved drive, or trailer). All highway truck tires singles include: increased payload vehicle stability/control during tire air loss. have load limits established for tires used weight and volume due to lower tire/ in normal highway service. Therefore, wheel weight/volume, ease of maintenance Matching Tires For when selecting a tire for service, both (no mismatched tires, etc.), reduced Speed And Axle Weights the carrying capacity and speed inventory, improved fuel economy, and implications must be considered. sometimes more uniform wear in free- As mentioned earlier, there are drive For example, when selecting tires rolling trailer applications. Possible train/gearing considerations which must for a tractor-trailer combination with legal restrictions of nonsteer axle be made at the original equipment or a gross combination weight (GCW) application of wide base singles should replacement level when utilizing low of 80,000 lbs. and an axle weight be thoroughly investigated before profile tires. These involve engine RPM, distribution of 12,000 lbs. on the steer, finalizing size selection. transmission, drive axle gear ratio and 34,000 lbs. on the tandem drive, and Original equipment fitment of wide tire RPM. The objective is to obtain the 34,000 lbs. on the tandem trailer axles, base singles offers the potential for most fuel efficient engine RPM/ground common conventional tire sizes used lowering the center-of-gravity and thus speed relationship consistent with are 295/75R22.5 (275/80R22.5), improving the stability of vehicles such service condition requirements. 285/75R24.5 (275/80R24.5), 11R22.5 as tankers. In retrofit applications, care The effect on road speed at the and 11R24.5 Load Range G. The must be taken to properly select wheel/rim same engine RPM, using a 55 mph base, load and inflation tables (from the offsets to maintain a tracking width for depends upon which conventional sizes Engineering Data Book for Over-the- acceptable stability. A common way to and which low profile diameters are Road Truck Tires or www.goodyear.com involved. Generally, if the percent /truck) for these sizes are shown in Table 2.

Table 2 TABLE 2 Tire Load Limits (lbs.) At Various Cold Inflation Pressures (The Pressure is Minimum for the Load, Maximum Speed of 60 MPH) Inflation Pressure (psi) Size Usage 70 75 80 85 90 95 100 105 110

11R22.5 Dual 4380 4580 4760 4950 5205(F) 5415 5625 5840(G) 5895 Single 4530 4770 4990 5220 5510(F) 5730 5950 6175(G) 6320 11R24.5 Dual 4660 4870 5070 5260 5510(F) 5675 5840 6005(G) 6205 Single 4820 5070 5310 5550 5840(F) 6095 6350 6610(G) 6790 295/75R22.5 Dual 4500 4690 4885 5070(F) 5260 5440 5675(G) 5800 6005(H) Single 4500 4725 4945 5155 5370 5510(F) 5780 5980 6175(G) 285/75R24.5 Dual 4540 4740 4930 5205(F) 5310 5495 5675(G) 5860 6175(H) Single 4545 4770 4990 5210 5420 5675(F) 5835 6040 6175(G)

(F) = Load Range F (G) = Load Range G (H) = Load Range H

12 S ECTION T WO Tire Selection

Therefore, with conventional tire is not an exact science, but there are • maintenance training for personnel sizes, it would require at least an 11R22.5 certain general rules and guidelines •retreadability/repairability costs tire with a carrying capacity of 6,175 lbs. which, if followed, can lead to selecting and servicing at 105 psi on the steer axle (which would a tread design that will give the maximum • warranty and adjustment servicing be the most critical for load and single desired performance for the service • leading edge or “experimental” application).The 11R22.5 would be more application in a particular fleet. In order product availability than adequate for drive and trailer axle to help select the right tread design, refer •effects of non-standardization applications. In low profile sizes, the to Technology & Maintenace Council RP •effects of tire down-sizing on vehicle 285/75R24.5 at 105 psi would have the (Recommended Practice) 220, Tire Tread gearing and braking adequate carrying capacity for the steer Design Selection. • timing for phase-in or changeover as well as the drive and trailer axle loads. programs The Tire and Rim Association has Fleet Operation • legal or contractual requirements established inflation pressures for load Considerations limits at various speeds for truck tires Retreadable Tires used on improved surfaces. Consult When evaluating the many tire options available for any given vehicle Retreading your worn tires or the Tire and Rim Association table or purchasing retreads from a dealer can individual tire manufacturer for specific application, there are numerous management considerations in addition provide new tire service and performance recommendations to meet your at a fraction of the cost of a new tire. operating condition. You can contact to the mechanical considerations already covered. While these considerations When selecting new tires, purchase The Tire and Rim Association at those that are designed to be retreadable. 330-666-8121 or www.us-tra.org. apply most directly when spec’ing out new equipment, they also can be used To insure retreadability, follow prescribed to reevaluate tire selection prior to maintenance and avoid regrooving Tread Design Selection tire replacement. which may damage the valuable casing. The selection of the proper tread Fleet Operation Considerations Retreaded Tire Considerations design for an intended application is • availability of various products and • provide equivalent service and very important to the fleet that wishes service maintenance performance to obtain the maximum potential from • tire purchase price vs. performance •reduce overall cost-per-mile tires and thereby lower tire expenses. (cost-per-mile) • conserve natural resources Selection of the proper tread design • financial inventory investment and • tread designs available for all space requirements applications Figure 2.2: Tire Construction

Tube

Flap

One-Piece Rim Multipiece Rim Rim Diameter Difference — 2-1/2 inches

Tube-Type Tire Tubeless Tire

13 Tire Selection S ECTION T WO

Overall Assembly Width Dual (or Center-to-Center Spacing)

Vehicle Clearance (V/C)

Tire Section Tire Section re Clearance

Width Ti Width

Wheel Offset Wheel Offset

Figure 2.3: Overall Width, Dual Tires

Common aspect ratio categories of medium truck tires are as follows: -98 Tube-type conventional sizes (10.00R20) Section Height -88 Drop center tubeless (11R22.5) = .75 Aspect Ratio -70-75-80 Low profile (295/75R22.5, 255/70R22.5) Section Width -65 Wide-base singles (18R22.5, 445/65R22.5)

New Tire Dimensions

Overall Diameter Section Height

Rim Width

Section Width Overall Width

“Aspect Ratio” is defined as the percent of the section height to the section width of the tire.

Figure 2.4: Aspect Ratio

14 S ECTION T WO Tire Selection

Standard Aspect Tires Low Profile Tires

11 R 22.5 295 / 75 R 22.5 Rim diameter in inches (15'' tapered bead) Rim diameter in inches

Radial Radial Aspect Ratio

Cross Section (inches) Cross Section (mm)

More recently the trend has been towards low profile tires. These are usually tubeless tires designed for either 22.5 or 24.5'' diameter wheels. The most common low profile tires are listed below showing conventional sizes which they normally replace:

Low Profile Sizes Conventional Sizes 295/75R22.5 (275/80R22.5) 10.00R20, 11R22.5 285/75R24.5 (275/80R24.5) 10.00R22, 11R24.5

Width

Standard Aspect Radial Tire 90-series (11R22.5)

Height is 75% of Width Low Profile Radial Tire 75-series (295/75R22.5)

Figure 2.5: Sizing Definition *Information courtesy of The Maintenance Council (TMC) — Recommended Practices Book

15 Tire Selection S ECTION T WO

TIRE SELECTION PROCESS WORK SHEET STEP 1 Record maximum axle weights expected during vehicle operation.

Axle Weights Steer Drive Drive/Trail Trail Trail STEP 2 Check types of service

______Line Haul —Travel on interstate and normal highway roads at maximum speeds with runs over 250 miles. ______Local — Most travel between and around city areas, with runs generally less than 250 miles. ______On-Off-Road — Travel on some highway and secondary roads with possible travel on gravel/dirt roads. ______Off-Road — Travel on mostly secondary and gravel/dirt roads with a potential for tread cutting due to rocks, debris, etc. STEP 3 Determine size restrictions

1. If spec’ing for new equipment, provide for adequate tire clearance and brake compatibility. a. Minimum tire diameter due to brake restrictions ______b. Maximum tire diameter desired ______

2. If retrofitting tires on existing equipment, will rim size change? a. [ ] No (State Rim Size) ______b. [ ] Yes (Select new rim size in Step 10)

If wheel size becomes larger (change from dual tires to wide-base tires or to larger dual tires), determine present tire clearances: (1) Vertical Tire Clearance ______(2) Front Wheel Clearance ______(3) Overall Width of Present Tire ______(4) Overall Diameter of Present Tire ______(5) Current Wheel Offset ______(6) Overall Width Across the Tires ______STEP 4 Write in type of tires to be used — Duals or Wide-Base ______STEP 5 Write in type of construction to be used — Radial or Bias ______

16 S ECTION T WO Tire Selection

STEP 6 Write in type of air retention construction — Tube-type or ______Tubeless (This will be determined by the type of rims to be used.) STEP 7 Write in aspect ratio to be used ______(This step may be incorporated into Step 8.) STEP 8 Select tire size from Tire and Rim Association tables or tire manufacturers’ data books using the tire described in Steps 4 through 7. Do this by cross checking the axle weights and speed restrictions to be sure the tires can carry the maximum axle load recorded in Step 1 at operational speeds.

Tire Size ______Dual Load ______Single Load ______at ______psi

If maximum loads cannot be attained with the initial tire desired, a change in either Steps 3(1), 4, or 5 must be made. Repeat Step 8 until a tire size with the necessary carrying capacity is selected. STEP 9 Write in selected tire’s dimensions from Tire and Rim Association tables or tire manufacturers’ data books.

Overall Diameter ______

Overall Width ______

Revolutions per Mile ______

1. If spec’ing new equipment, redesign space restrictions if adequate clearance and brake compatibility are not afforded, or return to Step 8 and select another size tire. 2. If retrofitting tires on existing equipment and larger size tires than presently used are selected, determine clearances:

a. Vertical Clearances:

Vertical Tire Clearance of Present Tire ______

Overall Diameter of Present Tire + ______

= ______(Subtotal)

Overall Diameter of Selected Tire - ______

Vertical Tire Clearance = ______(Consult the vehicle or suspension manufacturer for minimum clearance required.)

Overall Vehicle Height ______

17 Tire Selection S ECTION T WO

b. Front Tire Clearance:

Clearance of Present Tire ______

Overall Diameter of Present Tire + ______

= ______(Subtotal)

Overall Diameter of Selected Tire - ______

Front Tire Clearance = ______(Must be a positive number.)

c. Overall Width:

Overall Width Across the Present Tire ______

Overall Width of one current - ______outside tire

= ______(Subtotal)

Overall Width of one selected + ______outside tire

= ______(Subtotal)

Offset of both current outside wheels - ______

= ______(Subtotal)

Offset of both selected outside wheels + ______

Overall Width (Must be 102'' or less.) ______

If all clearances are not suitable, return to Step 8 and select a smaller size tire. STEP 10 Select wheel/rim from Tire and Rim Association tables or wheel/rim manufacturers’ catalogs. Check to see that load and inflation pressure ratings are adequate (compare with Single Load and Pressure in Step 8).

Wheel Size ______Load Rating ______at ______psi STEP 11 Select tread designs for steer, drive, and trailer positions using Technology & Maintenance Council Recommended Practice 220, Tire Tread Design Selection. Call 800-ATA-Line to order. STEP 12 Incorporate fleet operation considerations at this point. Compute gear ratio changes if appropriate.

18 Mounting S ECTION T HREE Procedure

Mounting Procedure

It is essential that good mounting procedures

be followed in order to obtain optimum tire

performance and operating efficiency. Also,

tire and rim servicing can be dangerous.

To prevent serious injury, be sure you

know, understand and follow all procedures

and safety instructions.

19 Mounting Procedure S ECTION T HREE

SAFETY INSTRUCTIONS LUBRICATION Do not mount or demount tires without proper training. Wall charts containing mounting and demounting instructions for all on-highway rims should be available through your normal rim supplier. “Safety Precautions for Mounting and Demounting Tube Type Truck/Bus Tires” are also available Figure 3.1 Lubricate areas shown by arrows through the United States Department of Transportation, National Highway A non-water base commercial bead Traffic Safety Administration, lubricant should be used since water in Washington, DC 20590. Inspect wheel mating surfaces for chaffing, corrosion the tire can cause excessive rim corrosion www.nhtsa.dot.gov or pitting. problems. However, thin vegetable oil soap solutions with a water base are approved. Lubricants which contain a WHEEL INSPECTION rust inhibitor can be an advantage. Avoid GUIDELINES the use of excessive lubricant Figure 3.1. Never use anti-freeze, silicones, Remove any and all cracked wheels or petroleum based lubricants. from service. Cracked wheels not removed from service will fail.

Figure 3.2 Area of tube stretched thin due to improper Inspect wheels for sometimes small cracks emanating Mating surfaces should be clean, smooth, and flush lubrication and mounting. from stud holes. so as to permit uniform distribution of clamping and torquing forces. When a tube and flap are not properly lubricated before mounting, they will be stretched thin in the tire bead and rim region Figure 3.2. This will cause premature failure.

These cracks will continue to grow outward, through the “dish” or between stud holes.

Remove wheels from service with excessively worn mating surfaces and/or worn or “wallowed” stud holes.

20 Mounting S ECTION T HREE Procedure

to remove any burrs or nicks on the tire side of the rim. These may damage the Area of Excessive tire during mounting or in service. Be Flexure very careful to clean all dirt and rust from the lock ring and gutter. This is GG important to secure the lock ring in its Ring Possible proper position. A filter on the air Flap and inflation equipment to remove moisture Tube Pinch GG from the air line helps to prevent Ring corrosion. Drain the air tank frequently. The filter should be checked periodically to see that it is working properly. Bead Check rim components periodically Properly Seated Bead Not for cracks. Replace all cracked, badly Properly worn, damaged and severely rusted Seated components with new parts of correct Figure 3.3 Improper bead seating size and type. When in doubt replace. Mark or tag the unusable parts as scrap Always use lubricant when mounting IRE IM LEANING and remove them from the service area. radial truck tires to ensure proper T & R C Do not, under any circumstances, bead seating and to prevent eccentric To prepare the tire, first clean and attempt to rework, weld, heat, or braze mounting. The more flexible sidewall of dry the inside with an air hose. Inspect any rim components that are cracked, the radial tire makes the use of lubricant for loose material inside. A small piece broken, or damaged. Replace them with in the bead area more critical than for of paper left inside a tube type tire can new parts or parts that are not cracked, bias ply tires which have stiffer sidewalls. chafe a hole in the tube and cause a flat. broken, or damaged and which are of If the bead is not properly seated on Dust the inside of the tire sparingly with the correct size and type. either a 2-piece or 3-piece rim and dry soapstone to prevent the tube from Make sure matching parts are being becomes “hung-up,” usually on the sticking to the tire. Do not let soapstone assembled. Check DOT chart, your removable flange side of tube type tires, accumulate in the tire. distributor or the manufacturer if you the lower sidewall area flexes excessively Also inspect and clean the tire beads have any doubts. under load, and irregular treadwear and to remove any accumulation of corrosion cracking in the lower sidewall bead area material or rubber that may be stuck to often result. Improperly seated beads it. Wipe the beads with a dry cloth can also produce severe truck vibration until clean. and cause chafing through the lower Clean rims to remove dirt, surface sidewall down to the wire. rust, scale and rubber build up. Repaint When the bead is not properly seated, to stop the detrimental effects of the bead toe is lifted, and the flap may corrosion and facilitate checking and be forced under the toe Figure 3.3. tire mounting. Be sure to clean the tire Continued up and down flexing of the seat areas thoroughly to insure proper toe can cut through the flap. As this fitment of the tire and to eliminate process continues, the tube becomes the potential for air leaks in tubeless pinched and may fail suddenly. assemblies. Also file or use emery cloth

21 Mounting Procedure S ECTION T HREE

ASSEMBLY OF TUBES & FLAPS TIRE TUBE FLAP Always install a new radial tube and a Insert the tube into the tire and new radial flap in a new tire. Use only partially inflate it to round out the tube. tubes designated for radials and make Apply rubber lubricant to the inside and sure the proper size tube and flap is used. outside surfaces of both beads and to WARNING Never use undersized tubes. Certain the portion of the tube that appears Always use a safety cage or precautions must be taken when mounting between the beads. Do not allow approved safety device and used flaps, or damage to the tire and lubricant to run down into the tire. extension hose with air gauge tube will result. Apply the lubricant with a cloth, and clip-on air chuck for airing a tire on a multi-piece rim or New truck and bus flaps can be used swab, or brush. single piece rim. with any one of several different tire and For detailed, illustrated instructions rim sizes as recommended. But, once on procedures and proper use of tire used, the flap must be remounted in the tools in mounting and demounting Tube type tires should always be same size tire and on the same size rim Goodyear radial truck tires on various aired once before the valve core is from which it was removed. Always use types of rims, see the wall charts installed. This will eliminate confusion a flap of adequate width to prevent available through RMA (www.rma.org). in inflating a tire twice. All tube type tube pinching. After mounting and before inflating radial tires should be inflated twice. As a precaution against flap failure, the tire, inspect all components of To inflate twice, the tire is inflated mark the tire and rim size on the flap at multipiece rims to make sure they are in to full inflation pressure, then all the the time of removal (if inspection shows place. See that tires are properly mounted air is let out and the tire is reinflated. that it is not damaged and can be used and seated on the rims by checking the The first inflation seats the bead of the again). When the flap is again mounted, distance between the tire GG ring and tire, but over stretches the tube and this marking protects against the danger the rim flange. This distance should be flap in the area between the bead toes. of misusing the flap with the wrong size the same all the way around the tire; Completely deflating the tire allows the tire and rim. that is, the rim flange must be concentric tube and flap to relax. A partial deflation with the GG ring (refer to the photograph doesn’t get the job done. The full Figure 3.4 below, and Figure 3.3 on deflation and reinflation stretches CAUTION page 19, for GG ring location on tire) the tube and flap uniformly. Used flaps cause tube failure unless and the distance must be the same for Important: During the first inflation, mounted with the size tire and rim both sides. the airing should be stopped at about 10 originally used. psi, and the side ring or lock ring should be checked carefully to make sure it is properly seated. Also, it is recommended The valve core provides a temporary that the side ring or lock ring seating air seal while air pressure checks are be checked at 10 psi during the being made, but it will leak air slowly if second inflation. the cap is loose, missing, or damaged. Use a sealing-type valve cap. A metal cap is preferred but a sealing-type nylon Figure 3.4 Use of GG ring to indicate correct mounting cap is acceptable. WARNING In the case of used tires and tubes, Never, under any circumstances, recondition the valve stem every time a attempt to seat rim components tire is mounted. Recondition the threads by tapping with mallet when tire on both the inside and the outside of is inflated or partially inflated. the stem with a valve stem rethreader Deflate tire first. tool. Install only new valve cores. Used or dirty valve cores may be defective. Don’t take a chance. Valve cores must Install a sealing-type valve cap finger be stocked in clean closed containers at tight. A valve cap has two functions to all times, since a small particle of dirt perform. The first is to keep dirt from will render a core ineffective. damaging the valve core sealing surface. The second, is to provide an air seal for

22 Mounting S ECTION T HREE Procedure

TUBELESS TIRE MOUNTING the valve. A valve cap, therefore, must For mounting tubeless tires, the be durable. procedure is about the same as for tube The black plastic cap that sometimes type tires except that it is not necessary comes on a new tube is not a valve cap to inflate twice. Cleaning the rim is WARNING and will leak air at the high inflations again critical because the tire depends Always use a securely held safety used in truck tires. Its purpose is to keep on the rim for its air seal. Make sure the cage and extension hose with dust and dirt out of the stem during inside of the tire is clean and dry. If tires clip on air chuck for airing the tire. Rapid air loss can propel shipment, protect the threads of the have been stored outdoors, any water in the assembly. stem, and shield the folded tube against the tire must be removed and the tire abrasion by the threads. The plastic cap dried before mounting. Water vapor in threads are easily stripped; the plastic the inflation air tends to cause rim cap will crack in cold weather and will corrosion. The valve stem must be melt if the stem comes in contact with inspected to make sure it is tight in the INSTALLATION the brake drum. A metal valve cap rim and that the rubber grommet Installation of the tire on the vehicle contains a rubber gasket which provides between the rim and stem is in good is the final step. When pulling a tire an air seal; a plastic cap contains none. condition. from stock, check the air pressure against Therefore, always use a metal cap or a To install the tubeless tire on the rim, the desired value. When tires are to be self-sealing nylon cap. lubricate both bead seats of the rim and mounted as duals, make sure that the Valve extensions, or “air-through” both tire beads to ensure damage-free two tires are actually the same size. valves are not a substitute for caps, since and uniform mounting. Bead lubricant (See Matching of Duals on page 25.) they are still subject to core seal leaks at must also be used during demounting to Measure the outside diameter of high pressure. Valve extensions require a avoid damage to the bead area. Due to every tire after it is mounted and inflated sealing-type valve cap. their greater sidewall flexibility, it may and before it goes into stock. The Bend the valve stem to its proper be necessary to use an inflation aid to diameter should be written on the tread position. If it is left flat and touching help seat radial tubeless tire beads. For so that it is visible when the tire is in the rim, the valve cap will be difficult to detailed mounting and demounting the spares rack. Then by simply looking remove and accurate air pressure checks instructions, refer to the wall charts at the treads of the spares in stock, a will be hindered. (If it is easy to check available through OSHA Occupational replacement tire of the correct diameter the pressure in a tire, it is more likely to Safeaty and Health Administration to match an already mounted dual can be checked.) The stem should not be (www.osha.gov). When using tire irons, be selected. bent up enough to cause it to touch the exercise caution to prevent damage to There are many ways of measuring brake drum. Heat from the drum will be the tire or rim. the size of a tire, but two ways appear conducted along the brass valve stem to Check that the distance between to be more satisfactory than the others. the tube/flap area around the stem base the tire GG ring and the top of the Both involve measuring the complete and cause decomposition of the rubber. rim or wheel flange is uniform all circumference of the tire. The first uses This will lead to eventual tube failure. around the tire, and that the distance a 14-foot endless steel mating tape. In such a heated valve stem, the valve is the same on both sides of the tire. This is a steel band that is formed into a core seal may also be ruined. If this distance is not uniform, the hoop. The hoop is slipped over the tire, After the tire is mounted and inflated, bead is not properly seated. pulled up tight, and a reading made. the tire/wheel assembly should be put If the GG ring in no concentric with The second type is a pocket-size steel into stock for 24 hours to permit a test the rim flange, it is recommended that tape. With this it is necessary to hook of its air retention. Just prior to being the “inflate-twice” procedure also be the end in the tread and roll the tire one put in service, the pressure in the tire used in mounting tubeless tires in order revolution, which brings the tape end should be checked and compared with to seat beads properly. back around and permits a reading of the initial value applied. If the pressure the circumference. is more than 5 psi lower, the tire should Another way of measuring tires be withheld from service and checked uses calipers that measure tire diameter. for a leak. The tape method is preferred because it provides an average diameter rather than any one particular diameter measurement.

23 Mounting Procedure S ECTION T HREE

1 2 1 10 8 7 4 3 6 5 5 6 4 7 2 9 3 8

Figure 3.6 Proper sequence for tightening stud nuts on Figure 3.8 Proper sequence for tightening stud nuts on an 8 stud system. 10 stud system. DEMOUNTING Always deflate any tire to be removed prior to loosening rim or wheel nuts. 1 Bead lubricant must be used when demounting tubeless tires. 3 4 Figure 3.5 Measuring with pocket size steel tape.

On demountable rims, lugs should 5 2 be tightened uniformly in a triangulated or criss-cross sequence to achieve trueness of the rim on the wheel. Lug nuts should be torqued properly so they do not loosen in use. On disc wheels, Figure 3.7 Proper sequence for tightening stud nuts on stud nuts should also be drawn up and an 5 and 6 stud systems. tightened in a criss-cross sequence. See rim and wheel manuals for more installation details. Lug or stud nuts should be checked for tightness after the first 100 miles of travel and once 1 each week thereafter. 6 3

45 2

24 Mounting S ECTION T HREE Procedure

MATCHING OF DUALS Mismatched duals have the same effect In addition to matching diameters and Matching dual tires is important on the life of tires as low inflation or inflation pressures on dual installations, to insure even wear and load sharing overload. An underinflated tire on a dual it is very important not to mix radials capabilities. Tire circumference of duals assembly shifts its share of the load to and bias ply tires on the same axle due should be as close as possible with a its mate, which then becomes overloaded to different load/deflection characteristics maximum tire circumference tolerance and frequently fails prematurely. A of these two types of tires. Radial tires of 3/4" for tire sizes 8.25R20 and 1-1/2" difference of 15 psi inflation may result deflect more under a given load than maximum circumference tolerance for in the lesser inflated tire supporting 500 bias ply tires. If radial and bias ply tires tire sizes 9.00R20 and larger. pounds less than the tire with the proper are mixed in dual installations on the When mounting duals on a truck, inflation. A similar action occurs when same axle, the bias ply tires will bear there will generally be some difference one tire’s diameter is smaller than its the greater part of the axle load and in the diameter of the two tires (within mate. A difference of 1/4 inch in diameter may operate in an overloaded condition the limits described above). Mount the may result in the larger tire carrying 600 that will lead to reduced mileage and small tire on the inside. The outside tire pounds more than the smaller. The shift early failure. wears faster than the inside tire. As it in load becomes more prevalent as the Radial tire overall diameter will govern wears its diameter will approach that of difference in diameters or inflation the revolutions per mile obtained from the inside tire. Additionally, any crown becomes greater. a given tire. It is necessary to closely on the road will favor the placement of Improperly matched duals are subject match tire revolutions per mile with the smaller diameter tire on the inside. to rapid treadwear because the larger tandem drive axle units coupled directly At the time of mounting duals on a tire carries more load and will wear fast . together, as when an interaxle differential vehicle, locate the two valves diametrically Although the mismatched duals have does not exist or is locked out. Otherwise, opposite (180 degrees apart) for different diameters, they must rotate at the drive transmission may freeze up or accessibility. Hand holes on disc wheels the same speed. The smaller tire then fail in some way, and/or excessive slip must be located so that the inside valve also wears unevenly because it is forced on one of the sets of tires will lead to a is accessible. to scuff over the road. The overall result loss in traction and uneven wear. is abnormal and unequal treadwear for It is important that the tires of tandem both tires. driving axles be inspected and matched Improperly matched duals may also at regular periods, as determined by the lead to sudden air loss as a result of one type of service. tire being required to flex severely in doing more than its share of the work.

25 Mounting Procedure S ECTION T HREE

SPACING OF DUALS Proper spacing between dual tires is important. Too often, the service Section Width Section Width rendered by dual tires is sharply reduced because of insufficient spacing. It is a condition caused by either (a) oversized tires or (b) improper rims and wheels.

Tires mounted too close together do not re Clearance Ti ehicle Clearance

allow proper air circulation to dissipate V tire heat. Heat increases tire tread loss CL CL rate and reduces tire durability. When a truck is heavily overloaded, insufficient spacing can cause the sidewalls of the idth W Spacer duals to rub together, wear off rubber, and become overheated due to continuous friction. If the space between duals is too Offset Offset great, there will be excessive dragging Dual Spacing and scuffing of the outside tire each time a turn is made. Also, check overall Figure 3.9 Cross-section through typical dual installation vehicle track width to assure compliance with width laws. Rim offset determines dual spacing PACERS Note that proper dual spacing for and affects vehicle clearance and possibly S radial tires is the same as for bias ply. overall vehicle width. Any change in Spacer installation procedure is as An understanding of the geometry offset of the inside rim will change follows: of a dual tire installation is important. vehicle clearance proportionally. Any 1. Examine spacer brand to be sure it A cross-section through a typical dual offset changes of the outside rims will is not damaged, bent, or distorted. installation is shown in Figure 3.9. change the overall distance across the It should be perfectly circular. The dual spacing of the installation is vehicle from outside tire wall to outside 2. Do not roll vehicle, wheels, axle, the sum of the rim offsets and the tire wall. or assemblies on spacers. spacer width. Both load and inflation must be 3. Position inside rim over cast spoke To determine tire clearance, subtract considered in selecting rim size or wheel as close as possible to the the section width from the figure for type. Consult rim manufacturer for mounting level. dual spacing. Use the loaded section recommended rim style for extra ply 4. Push spacer band over cast spoke width (LS) at rated load for a more exact rating tires. wheel with consistent pressure on clearance figure. The loaded section both sides. Avoid cocking band. width can be found in the Goodyear Achieve snug fit against spokes and Truck Tire Engineering Data Book, or inside rim gutter edge. the width of a tire can be measured 5. Turn spacer band on wheel to check under load. concentricity. Dual spacing and tire clearance can 6. Position outside rim, install outer be varied by changing spacer width. rim clamps and tighten nuts To increase spacer width, however, the evenly. Tighten nuts gradually in mounting width on the dual wheel must a criss-cross sequence across the be great enough to accommodate a diameter of the wheels. Consult wider spacer. The distance from the rim manufacturer’s recommendations outside tire wall of one dual assembly to for proper torque range. the outside tire wall of the assembly on 7. Examine clamps to be sure they the other side of the truck will be made have not bottomed out. Check rim greater when spacer width is increased. edges to be sure they consistently If this distance is the maximum width of meet the spacer band edges. the vehicle, state laws governing truck 8. After road service, recheck torque. width must be considered.

26 Mounting S ECTION T HREE Procedure

PROPER MATCHING OF RIM PARTS CORRECT Accuride 5˚ or Motor Wheel “CR” or “FL” Flange Motor Wheel or Accuride “CR” or “FL” Side Ring Motor Wheel or Accuride “CR” or “FL” Lock Ring Proper Fit

Proper Fit Motor Wheel or Accuride “CR” or “FL” Base Motor Wheel LW and LB Base Accuride or Budd LB Base Motor Wheel LW Side Ring Accuride or Budd LB Side Ring Proper Fit Motor Wheel or Accuride “CR” and “FL” Bases and Components Interchangeable With Accuride “CR” and “FL” Motor Wheel “LB” Bases and Components Interchangeable With Accuride and Budd “LB”

INCORRECT Accuride 5˚ Lock Ring “CR” / “FL” Side Ring “LW” or “LB” Base “CR” or “FL” Base Bead Seat Too High Loose Fit

Bead Seat Too High Improper Seating

“CR” or “FL” Flange & Lock Ring “LW” or “LB” Base

“LW” Side Ring “CR” or “FL” Base Loose Fit

Improper Seating

Figure 3.10 Correct and incorrect matching of rim parts

Most highway rims look alike, but all In addition to the safety problems Mismatched assemblies that result vary somewhat in certain construction posed by mismatched rings and bases, in a low bead seat can sometimes be features. Variances between rims of mismatched components can cause special recognized by rust on the bead face. different types make part mixing problems in tire, flap, and tube wear. Such assemblies allow: hazardous. A close, proper fit between Mismatched rim components that • Irregular bead base wear rim parts is essential to long tire life as result in a high bead seat often achieve • Off-center mounting, higher well as operating safety. Although side bead seating over only a portion of the imbalance, more vibration rings, flanges, and lock rings of different rim circumference. This causes: • Rotational slippage of tire on rim types appear to be properly seated, • Vibration • Valve stem tear-outs difficult to detect gaps are often present. • Uneven wear Rim component mismatch — with The illustrations in Figure 3.10 • Severe rim chafing at top of flange either high or low bead seat diameter — show correct, safe matchings of rim • Larger gaps in two piece rim flanges permits bead rocking which can cause parts. Mismatched rings and bases, which cut chafer the tire bead toe to cut through the which almost always create an unsafe • Torn chafers at bead heel flap and tube. This additional bead operating condition are also shown. For • Cut bead heels, which generally movement can also cause the flap edge more information, refer to Department identify this condition to cut through the tube. In either case, of Transportation (DOT) Multipiece • Bead base irregular chafing a flat tire is the eventual result. Rim/Wheel Matching Chart. • Lower sidewall separation due to (www.dot.gov) stress concentration at flange top • Broken beads

27 Mounting Procedure S ECTION T HREE

SAFETY PRECAUTIONS Inspection: Precautions And Reasons For Precautions •Clean rims and repaint to stop • Do not, under any circumstances, • Don’t be careless or take chances. detrimental effects of corrosion and attempt to rework, weld, heat, or braze If you are not sure about the proper facilitate checking and tire mounting. any rim components that are cracked, mating of rim and wheel parts, consult Be very careful to clean all dirt and broken, or damaged. Replace with a rim and wheel expert. This may be rust from the lock ring and gutter. new parts or parts that are not cracked, the tire man who is servicing your This is important to insure that the broken, or damaged and which are fleet, the rim and wheel distributor lock ring seats in its proper position. of the same size and type and are in your area, or the manufacturer’s A filter on the air inflation equipment compatible with the other parts. sales engineer. to remove the moisture from the air Heating may weaken a part to the Failure to exercise proper care can line helps prevent corrosion. The filter extent it is unable to withstand forces result in serious physical injury should be checked periodically to see of inflation or operation. or death. that it is working properly. • Make sure correct parts are being • Don’t reinflate a tire that has been run Parts must be clean for a proper fit — assembled. Check your distributor flat or has been run at 80 percent or particularly the gutter section which or the manufacturer if you have less of its recommended operating holds the lock ring in proper position. any doubts. pressure, or when there is obvious or • Components that are cracked, badly Mismatched parts may appear to fit, suspected damage to the tire or wheel worn, damaged, bent, repaired, or pitted but when the tire is inflated may fly components. from corrosion must not be used and apart with explosive force sufficient Components may have been damaged must be discarded. When component to cause serious injury or death. or dislocated during the time the tire condition is in doubt, replace. was run flat or seriously underinflated. Parts that are cracked, damaged or excessively corroded are weakened.

28 Mounting S ECTION T HREE Procedure

MOUNTING AND INFLATION: Precautions For Potential Steel Cord Fatigue Damage Underinflated truck tires can be subject GOODYEAR STRONGLY • Goodyear’s long-standing policy to cord fatigue in the upper sidewall area RECOMMENDS THAT: and Occupational Safety and caused by over-flexing of the tire. This •Truck tires should be visually inspected Health Administration (www.osha.org) cord fatigue leads to a loss of strength of daily for cuts, snags, penetrations or Standard 1910.177, require that all the ply cords. When a tire loses air and puncturing objects. tubeless and tube type truck tires be is continued in service without remedial inflated in an OSHA approved •Proper tire inflation be maintained. action, it may sustain internal damage inflation safety cage in conjunction that could lead to failure upon reinflation • Highway truck tire inflations be with the use of an extension air hose or subsequent service. When such a checked at least weekly, or more equipped with a clip-on air chuck. frequently if operating conditions tire is reinflated, or removed from the • While this OSHA standard pertains dictate, using an accurate calibrated rim (for example, for tire repair or to medium truck tires, Goodyear air gauge. maintenance) and then remounted, strongly recommends these procedures inflation used to bring the tire to its • Any tires suspected to have been be used for all LIGHT TRUCK operating pressure may cause one or operated underinflated must be clearly tires also. more of the weakened cords to break. marked and segregated, so as to UNLESS THE PRECAUTIONS This cord failure causes an increase in prevent their accidental use prior NOTED ABOVE ARE CAREFULLY tension on cords adjacent to the broken to being thoroughly inspected by AND COMPLETELY FOLLOWED, cord, with the result that more of the a trained tire technician. SUCH FAILURE MAY CAUSE weakened cords may fail. This breakage •Tires that show discoloration and may continue until a rupture occurs in SERIOUS PERSONAL INJURY wrinkling of the innerliner, and/or OR DEATH. this area of the tire with accompanying weakness and distortion of the upper air loss, which is commonly referred to sidewall (indications of damage due as a Zipper Rupture. to underinflation) are to be scrapped. Permanent tire damage due to • After servicing the tire, inflate it to underinflated operation cannot always 20 psi OVER recommended operating be detected. Any tire known or suspected pressure in an APPROVED SAFETY to have run at 80% or less of normal CAGE USING A CLIP-ON CHUCK, operating inflation pressure could possibly EXTENSION HOSE AND PRESSURE have permanent structural damage and REGULATOR. Allow the tire to remain should be treated as having been operated overinflated for 20 minutes and then flat or underinflated. The tire should be deflate to the recommended operating demounted using proper precautions and pressure BEFORE removing from the should not be reinflated until the tire is safety cage. carefully inspected by a trained technician for determination of the cause of the inflation loss, and any possible strucural. damage. (See pages 29 - 31)

29 Mounting Procedure S ECTION T HREE

MOUNTING AND INFLATION: Precautions And Reasons For Precautions • Always match a tire (size) diameter If tube type, inflate tire to • Follow recommended mounting, designation with exactly the same rim approximately 75 psi pressure demounting, inflating and deflating diameter designation. Don’t assume (Grader, 50 psi). Then completely procedures for tires and rims as that it came in with proper size. deflate to remove buckles and uneven outlined in this manual. •Rims of different diameters and tapers stresses from the tube and flap before Misassembled parts may fly apart cannot be interchanged. reinflating to correct operating pressure. during inflation: check at 10 psi to • Don’t try to seat rings or other This repeat inflation is necessary to determine whether parts are in components by hammering while tire prevent buckles which may lead to proper position. premature tube failures. is inflated or partially inflated. • Don’t hammer on rims or components • Never introduce a flammable substance After completing inflation, check with steel hammers. Use rubber, lead, into a tire — before, during or valve and rim components in both plastic or brass faced mallets if it is after mounting. bead areas for leaks. Observe tire necessary to tap uninflated components lower sidewall circumferential groove’s together. Mallet faces should be in Doing so is unsafe and may result in concentricity with top of flange. If the internal tire damage or fire, rim good condition to avoid chips from distance between the groove and rim mallet face inside of the components. damage or a potentially dangerous flange varies by 1/8'' or more around Properly matched and assembled vapor remaining in the tire. Any of the circumference or from one bead components will seat without tapping. these conditions could cause serious to the other, the tire beads must If a part is tapped, it or the tapping personal injury during the mounting be unseated from the bead seat, tool may fly out with explosive force. and inflating procedure. relubricated and reseated. • When moving a tire or wheel with • Double check to make sure all • Never sit on or stand in front of, or a cable or chain sling, stand clear. components are properly seated over, a tire and rim assembly that is prior to and after inflation. being inflated. During inflation, always The cable or chain may break, lash • Always inflate in a safety cage or use a clip-on chuck with sufficient out and cause serious injury. use another restraining device that is length of hose to permit standing • Never attempt to weld on an approved by the Occupational Safety clear of the potential trajectory of the inflated tire/rim assembly or on a and Health Administration wheel components, and use an in-line rim assembly with a deflated tire. (www.osha.gov). valve with gauge or a pressure regulator Heat from welding will cause a sudden, • Don’t inflate a tire before all preset to a desired value when inflating drastic increase in pressure, often components are properly in place. a tire. When a tire is in a restraining resulting in a large, explosive force. Place assembly in a safety cage or use device, do not lean any part of your Deflated tires can catch fire inside the another restraining device and inflate body or equipment on or against the air chamber. restraining device. to approximately 10 psi. Recheck • Mixing parts of one type rim with those components for proper assembly. If parts are improperly installed they of another is extremely dangerous. Observe that the O-ring does not roll may fly apart with explosive force Always check manufacturer for out of its groove. If the assembly is sufficient to cause serious injury or approval if in doubt. not proper, deflate and correct. Never death. Rapid air loss can propel hammer on an inflated or partially an assembly. inflated tire/rim assembly. If the assembly is proper at approximately 10 psi, continue to inflate to fully seat the tire beads.

30 Mounting S ECTION T HREE Procedure

OPERATION: Precautions And Reasons SERVICING TIRE AND RIM ON VEHICLE: For Precautions Precautions And Reasons For Precautions • Always use rims recommended for the • Block the tire and wheel on the under the jack. Always provide for tire. Consult catalogues for proper opposite side of the vehicle before vehicle support with blocks just in tire/rim matching. placing the jack in position. case the jack should slip. • Don’t overload or overinflate tire/rim • Regardless of how hard or firm the The vehicle may shift, slip off the jack assemblies. Check for adequate rim ground appears, put hardwood blocks and cause injury. strength if special operating conditions are anticipated. Excessive overload or overinflation can cause damage to the tire and Inspection Procedures For Identification rim assembly. Of Potential “Zipper Ruptures” In Steel Cord • Never run a vehicle on one tire of Radial Medium And Light Truck Tires a dual assembly. The carrying capacity of the single tire Any tire suspected of having been and rim is dangerously exceeded, and operated underinflated and/or overloaded operating a vehicle in this manner can must be approached with caution. WARNING result in damage to the rim and tire or Completely deflate the tire by removing cause a tire fire. the valve core before removing the Permanent tire damage due to underinflation and/or overloading • Never use a tube in a tubeless tire/rim tire/rim/wheel assembly from the vehicle. After removing from the vehicle, cannot always be detected. Any assembly where the rim is suspected tire known or suspected to have of leaking. clearly identify the tire, so it will not be reinflated until carefully inspected by a been run at 80% or less of normal Loss of air pressure through fatigue trained technician, to determine the operating inflation pressure and/or overloaded, could possibly have cracks or other fractures in a tubeless cause of inflation loss, as well as any tire rim warns you of a potential rim failure. permanent structural damage damage resulting from underinflation (steel cord fatigue). Ply cords This safety feature is lost when tubes and/or overloading. are used with leaking rims. Continued weakened by underinflation and/or overloading may break use may cause the rim to burst with one after another, until a rupture explosive force. occurs in the upper sidewall with • Always inspect rims and wheels for accompanying instantaneous air damage during tire checks. loss and large explosive force. Early detection of potential rim This can result in serious injury or death. failures may prevent serious injury. • Never add or remove an attachment or otherwise modify a rim (especially by heating, welding or brazing) unless the tire has been removed and approval has been received from the rim manufacturer. Modification or heating of a rim or one of its parts may weaken it so that it cannot withstand forces created by inflation or operation.

31 Mounting Procedure S ECTION T HREE

Inspection Procedures For Tires Suspected Of Having Been Run Underinflated And/Or Overloaded Inspect Deflated Inspect Suspect Inspect Suspect Suspect Tires Mounted Tire Inflated Tires after A on the Rim – B to 20 psi — C Dismounting — LOOK for: LOOK for: LOOK for: cuts, snags, or chips exposing body distortions or undulations (ripples bead rubber torn to the fabric or cords or steel*; distortions or undulations and/or bulges); and steel*; cuts, snags, or chips exposing (ripples and/or bulges), using an indirect body cords or steel*; distortions or LISTEN for: light source, which will produce shadows undulations (ripples and/or bulges), left by any sidewall irregularities. any popping sound. using an indirect light source, which will If any of these conditions are present, produce shadows left by any sidewall FEEL for: the tire should be made unusable irregularities; creasing, wrinkling, soft spots in the sidewall flex area; and scrapped. cracking or possible discoloration of distortions or undulations (ripple and/or If none of these conditions are the innerliner; and any other signs of bulges); protruding filaments indicating present, dismount the tire to visually weakness in the upper sidewall. broken cords; and and manually inspect it, both inside If any of these conditions are LISTEN for: and outside. present, the tire should be made any popping sound when feeling for unusable and scrapped. *If no other soft spots or when rolling the tire. condition is present and a tire contains cuts, snags, or chips exposing body If any of these conditions are present, cords or steel, it must be referred to a the tire should be made unusable and full-service repair facility, to determine scrapped. *If no other condition is if it is repairable and not a source of a present and a tire contains cuts, snags, potential zipper. or chips exposing body cords or steel, it must be referred to a full-service If none of these conditions are repair facility, to determine if it is present, the tire may be returned to repairable and not a source of a service, using the procedures on the potential zipper. next page. If none of these conditions are present, place the tire/rim/wheel assembly in an approved inflation safety cage. REMAIN OUTSIDE OF THE TIRE’S WARNING TRAJECTORY. DO NOT PLACE HANDS IN SAFETY CAGE WHILE STAY OUT OF TRAJECTORY AS INSPECTING TIRE, OR PLACE INDICATED BY SHADED AREA. HEAD CLOSE TO SAFETY CAGE. Note: Under some circumstances, With the valve core removed, reinflate the trajectory may deviate from its the tire to 20 psi, using a clip-on air expected path. Always deflate tires before handling. Inflate only in chuck with a pressure regulator and safety cage. an extension air hose.

32 Mounting S ECTION T HREE Procedure

Inspection Procedures For All Tires Returning to Service (Including used, retreaded, or repaired, regardless of being suspect or not suspect) Inspect Dismounted Inspect Mounted Inspect Mounted Tires Tires (including Tires Inflated Inflated 20 psi OVER used, retreaded, to 20 psi — Operating Pressure — A or repaired)– B C LOOK for: LOOK for: LOOK for: bead rubber torn to the fabric or steel*; distortions or undulations (ripples distortions or undulations (ripples cuts, snags or chips exposing body cords and/or bulges); and and/or bulges): and or steel*; distortions or undulations LISTEN for: LISTEN for: (ripples and/or bulges), using an indirect any popping sound. any popping sound. light source, which will produce shadows left by any sidewall irregularities; creasing, If any of these conditions are present, Any tire suspected of having been wrinkling, cracking, or discoloration the tire should be made unusable underinflated and/or overloaded must of the innerliner; any other signs of and scrapped. remain in the safety cage at 20 psi weakness in the upper sidewall; If none of these conditions are present, OVER operating pressure for 20 minutes. FEEL for: with valve core still removed, inflate the If any of these conditions are present, tire to 20 psi OVER the recommended the tire should be made unusable soft spots in the sidewall flex area; operating pressure. During this step, and scrapped. distortions or undulations (ripples if any of the above conditions appear, and/or bulges); protruding filaments If none of these conditions are present, immediately stop inflation. indicating broken cords; and BEFORE removing the tire/rim/wheel assembly from the safety cage, reduce LISTEN for: the inflation pressure to the recommended any popping sound when feeling for operating pressure. REMAIN OUTSIDE soft spots or when rolling the tire. OF THE TIRE’S TRAJECTORY. If any of these conditions are present, Occupational Safety and Health Administration the tire should be made unusable and Standard 1910.177 requires all tubeless and tube-type scrapped. *If no other condition is medium and large truck tires be inflated using an present and a tire contains tears, cuts, OSHA-approved restraining device (e.g. safety cage) snags, or chips exposing body cords or barrier, and using a clip-on air chuck with a or steel, it must be referred to a full- pressure regulator and an extension air hose. While service repair facility, to determine the OSHA (www.osha.gov) standard pertains to if it is repairable and not a source of medium and large truck tires, RMA also strongly a potential zipper. recommends these procedures be used for all LIGHT If none of these conditions are present, TRUCK TIRES. place the tire/rim/wheel assembly in an approved inflation safety cage. REMAIN OUTSIDE OF THE TIRE’S TRAJECTORY. DO NOT PLACE WARNING HANDS IN SAFETY CAGE WHILE Mounting Tires Is Dangerous - INSPECTING TIRE, OR PLACE failure to follow the above and HEAD CLOSE TO SAFETY CAGE. Rubber Manufacturer‘s Association After properly seating the beads, with (RMA) “Demounting and Mounting the valve core removed, adjust the tire Procedures for Truck/Bus Tires” to 20 psi, using a clip-on air chuck with or “Demounting and Mounting a pressure regulator and an extension Procedures for Automobiles and air hose. Light Truck Tires” charts and safety precautions can result in serious injury or death. For more information visit www.rma.org.

33 Collecting & Storing Tire Information S ECTION F OUR

Collecting & Storing Tire Information

Keeping appropriate records of your tire

related data is the best source of information

on tire performance, because they summarize

your actual experience based on your

equipment, your drivers, and your operating

environment. They can help you to make

cost effective tire purchase decisions and

adjustments to tire and wheel maintenance

schedules to better control costs.

34 Collecting & Storing Tire S ECTION F OUR Information

COLLECTING & STORING TIRE INFORMATION BRANDING TIRES Depending on the size of your fleet, Several branding methods exist. Before A third method is “mold branding.” tire data can be kept using a computer- branding, you need answers to several This is done when the tire is being aided method or simple paper files. Large questions. What branding method is best manufactured. While this method offers fleets may need the huge information for the quantities of tires involved? On the best appearance, it’s available only storage capacity and the networking what part of the tire is it “safe” to brand? when large quantities of tires are ordered capability of a computer. Small fleets How deep can a tire be branded without and usually for only bias-ply tires. may find the expense and complications damaging the tire? Should you buy tires Use lower sidewall area. Most truck of computer-aided information storage branded to your specifications or brand tires have a special branding panel on unnecessary. Whatever the method of them yourself? Many fleets brand their the sidewall. It’s located on the lower storage, there are several common factors own tires. Others, particularly large fleets, portion of the sidewall where little involved in tire data collection. Items find it more cost-effective purchasing flexing occurs under normal use, thus recorded for tire performance records, tires branded by the manufacturer or reducing the chances of cracking. at a minimum, should include: distributor. Three common branding If your tires don’t have these panels, • Tire Size • Recommended methods include the “cold method,” then brand in the lower sidewall area • Tire Brand/Type Inflation “hot method” and “mold branding.” between the top of the rim flange and • Initial Tire Cost • General Cold branding is somewhat of a the “line” around the tire at its maximum • Vehicle ID Comments misnomer because some heat is part of width. Never brand near the maximum Number • Actual Inflation the procedure. In this method, pressure, section width area of a radial tire. That’s • Vehicle Mileage • Vehicle Removal air or hydraulic, is used to produce a the tire’s critical sidewall flexing area. at Installation Mileage brand that is legible and usually less If you’re branding tires without panels • Installation Date • Removal Date damaging to the tire than the higher and wish to brand both sides, then • Tread Depth at • Tread Depth temperature hot method. Another apply brands on opposite sidewalls Installation Removal advantage to cold branding is its ability 180 degrees apart. to emboss brand. Numbers and letters How deep? By building a base of information are raised much like the markings on In general, you should brand truck across the fleet, trends in tire performance a new tire. Embossed brands are less tires between 1/32 inch and 2/32 inch in can be established. damaging to the tire than the more depth. Brands less than this depth range • How does mileage of Tire A compare common recessed brands though often are often difficult to read. Those greater to Tire B? more difficult to read. can result in cracking that may propagate • Which tire brand produces the lowest Both cold and hot methods provide away from the branded area, or worse, cost per mile? permanent brands but the higher they may go deeper into the sidewall temperatures of a hot branding iron rubber. Eventually, these deep cracks • Which tire has fewest adjustments? encourage branding too deeply into the might reach the outer surface of the A similar file can be used to track tire sidewall. Also possible is overheating the casing cords. This could allow moisture performance through retread life. Again, rubber compound around the brand and into the casing which then could lead performance of various tread patterns, creating a brittle surface area that could to degradation of casing durability. retread suppliers, and casing manufacturers initiate sidewall crack. If care is exercised, can be closely followed. Decisions on the hot method using medium heat will future retread purchases can then be made yield acceptable results. Always strive on hard facts rather than perceptions for the lowest possible temperature to and guesses. produce legible brands without scorching Permanent identification of each tire sidewall rubber. can make the tracking from purchase to scrap easier. Tires could be branded, or a Radio Frequency Identification Chip could be added to the tire to provide a unique identity for that tire.

35 Collecting & Storing Tire Information S ECTION F OUR

RADIO FREQUENCY IDENTIFICATION TAGS RF TAG USAGE Passive radio frequency (“RF”) Fleets may use RF tags for tire record Having well documented tire identification devices can be molded keeping and maintenance as well as performance information allows intelligent into a tire or encapsulated in a patch inventory. To ensure that RF tags are decisions to be made on alignment and bonded to the inner liner of radial, easily read and correlated with the intervals, recommended inflation medium and heavy duty, tubeless truck proper tires, the following tire mounting pressures and tire brand or type choices. tires. Guidelines have been established procedures should be followed: Keeping appropriate records of tire by the Technology and Maintenance Council A. Always mount tires with the DOT information is a final step in achieving a (www.tmc.truckline.com) to standardize code side on the deep dish rim side lower cost per mile from tires. Having the identification information provided of disc wheels, the fixed flange side clear records not only helps decision by an RF transponder when it is installed of tube type demountable rims making but also provides documentation during the tire manufacturing process, and the adapter side of tubeless of tire problems to be addressed by your used in an aftermarket application demountable rims. tire company’s representative. in truck tires and provide minimum B. The DOT code should be aligned After all, your goal as well as the goal performance criteria for the use of with the valve stem so that local read of your tire representative is to provide this technology. RF tags can be located and found you with the best tire for the job and to The transponder is a single chip, easily except in cases where match get all the mileage and service out of solid state, electronic device with an mounting takes a priority. your tires that they can give. integral or external antenna. Each tag C. Local read tags will then be readable that passes within the radio frequency on opposite sides when mounted as transmission range of a reader/interrogator duals and will be readable on the will be energized and have its circuit inside of the steering axle except turned on. In turn, the tag will respond for directionally mounted tires. by transmitting its encoded identification. D. 360 degree read tags are not restricted The reader will receive the RF transmitted by mounting. code and translate it into an alpha- numeric tire identification.

36 S ECTION F IVE Inflation

Inflation

Proper inflation of radial truck tires is the

most important maintenance practice to

ensure long tire life. Once proper tire

inflation has been determined, it should be

maintained at that level as consistently as

possible. Loads carried may be increased/

decreased for a given tire inflation when

operating at reduced/increased speeds,

but underinflation must never be allowed

in over-the-road truck tires.

37 Inflation S ECTION F IVE

A tire requires proper air pressure on load and service conditions. Most data each axle position. That would be ideal, to adequately carry the load placed on contained in this book is taken from tables but impractical for many linehaul fleets. it. The “container volume,” material published by the Tire & Rim Association Equal inflation pressure properties and inflation pressure determine (T&RA). Its members, U.S.-based tire, To compromise, determine the proper the load carrying capacity of the tire. rim and wheel manufacturers, set the inflation pressure for each tire on the Figure 5.1 Your tires provide traction for technical standards for manufacturing vehicle and use the highest pressure. braking, accelerating and turning and those products in this country. Remember that overinflation is preferred must carry out these tasks for many Using the tables is quite simple. First, to underinflation. That makes the miles. Without proper inflation pressure, determine the maximum load that your compromise acceptable. tires cannot carry out these tasks as they tire is likely to encounter. Then, for your Also consider operating speeds. were designed to do. tire size/ply rating, find the load in the Vehicles operated at less than highway But what is the proper inflation for table that is close to but slightly more speeds can carry greater loads, as shown your tires? A simple answer would be than the maximum anticipated load. The in Table 3. great, but not practical. inflation pressure at the top of this column Using load/inflation tables can help is your minimum pressure for the load. Loads determine inflation you get the most from your current tires. All tire manufacturers offer load/ Duals vs. singles It can also help you choose future tire inflation tables that can be used to Note that loads are shown for single sizes based on your vehicles’ needs and determine the proper inflation pressure and dual applications. When you run their service conditions. at various loads. duals, the allowable load at any given Always check inflation pressures when Load/inflation tables for Goodyear inflation pressure will be less than with tires are cold. Never bleed air from hot commercial tires are published on the singles. That’s to minimize overloading tires to relieve normal pressure build-up. Web site www.godyear.com/truck and in the when one tire in a dual assembly is The normal increase in pressure due to Engineering Data Book for Over-the-Road underinflated and to compensate for service conditions will be 10 to 15 psi, Truck Tires. This book, available at your road crown. and this is allowable in a radial truck tire. Goodyear Commercial Truck Tire Center, Position is another consideration. Steer, It is particularly important to keep and is updated periodically with the latest drive and trailer tires may carry different moisture from the inside of any tires and sizes and types of commercial truck tires. loads, with steer tires normally handling we strongly encourage proper selection Section “L” in this data book provides the heaviest because they run as singles. of compressor equipment, air-line routing, the information you’ll need to determine To optimize tire performance, you may and the use of air dryers to avoid moisture the proper inflation for your tires based require different inflation pressures in in high pressure air used for inflation.

LOAD Container Volume

Figure 5.1

38 S ECTION F IVE Inflation

Table 3

TABLE 3 TRUCK-BUS TIRES The service load and minimum (cold) inflation must comply with the following limitations: SPEED RANGE INFLATION PRESSURE INCREASE LOAD CHANGES WITH SPEED (MPH) RADIAL PLY TIRES RADIAL PLY TIRES CONVENTIONAL (STD. PROFILE) WIDEBASE/METRIC (LOW PROFILE) CONVENTIONAL WIDE BASE/METRIC 65 MPH 75 MPH 65 MPH 75 MPH 65 MPH 75 MPH 65 MPH 75 MPH 71 thru 75 + 5 PSI None + 5 PSI None - 12% None - 12% None 66 thru 70 + 5 PSI None + 5 PSI None - 4% None - 4% None 51 thru 65 None None None None None None None None 41 thru 50 None None None None + 9% + 9% + 7% + 7% 31 thru 40 None None None None + 16% + 16% + 9% + 9% 21 thru 30 + 10 PSI + 10 PSI + 10 PSI + 10 PSI + 24% + 24% + 12% + 12% 11 thru 20 + 15 PSI + 15 PSI + 15 PSI + 15 PSI + 32% + 32% + 17% + 17% 6 thru 101) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 60% + 60% + 25% + 25% 2.6 thru 51) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 85% + 85% + 45% + 45% Creep thru 2.51) 2) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 115% + 115% + 55% + 55% Creep + 40 PSI + 40 PSI + 30 PSI + 30 PSI + 140% + 140% + 75% + 75% Stationary1) + 40 PSI + 40 PSI + 30 PSI + 30 PSI + 185% + 185% + 105% + 105% 1) On conventional tires apply load increase to dual loads and inflations only, even if tire is in single application. 2) Creep–motion for not over 200 feet in a 30 minute period.

Source: The Tire & Rim Association Yearbook

39 Inflation S ECTION F IVE

A tire’s cold inflation pressure will Since this difference is small, the effect The inflation pressure reading at change with altitude and temperature. of altitude change on tire inflation, in 0 degree F might happen when the truck The air pressure gauge reads the difference general, is not considered to be significant. is parked on a cold winter night. It will between the tire’s contained air pressure Ambient temperature effects on a increase rapidly, though, once the truck and atmospheric pressure. Atmospheric tire’s cold inflation pressure, on the other begins to run and the tires warm up. pressure changes 0.48 psi for every 1000 hand, is significant. Using as an example At the other extreme of ambient feet change in altitude. Assuming constant a tire with an initial inflation pressure temperatures, for example during the temperature and internal tire volume, of 100 psi at 60 degree F ambient summer, it is common to find tire inflation if a tire pressure gauge reads 100 psi at temperature, for each 10 degree F change pressures in the 115 to 120 psi range. sea level, for every 1000 feet increase in temperature, there is about a 2 psi We always caution operators not to in altitude, the gauge will read 0.5 psi change in the tire’s inflation pressure, bleed air pressure down on cold tires higher inflation pressure, see Figure 5.2. see Figure 5.3. when they are at these higher ambient temperature conditions. Always inflate 105 tires cold to the required pressure no matter whaat the ambient temperature is.

104 UNDERINFLATION Underinflation can have detrimental 103 effects on the performance of your tires and vehicles. Increased tire wear rate, irregular treadwear, reduced casing 102 durability and lower fuel economy are

Inflation Pressure (psi) some of the unnecessary costs incurred from tires not properly inflated. 101 Running on underinflated tires costs you in lost tread life and higher fuel 100 consumption. Tests conducted by Goodyear have shown that just 15 0 1000 2000 3000 4000 5000 Altitude (feet) percent underinflation of steer, drive and trailer tires results in about an 8 Figure 5.2 percent drop in expected tread mileage and a 2.5 percent decrease in miles per gallon, Figure 5.4. 120 100

110 90

100 80 Inflation Pressure (psi) 90 70 Expected Mileage (percent)

80 60 0 20 40 60 80 100 120 140 0102030 Ambient Temperature (deg F) Under Inflation (percent)

Figure 5.3 Figure 5.4 40 S ECTION F IVE Inflation

The damage doesn’t end there. When inflating or reinflating tires, With the capabilities of today’s truck UNDERINFLATION always use a tire safety cage. This holds tires, underinflation is also detrimental CAN CAUSE: true for both tube-type and tubeless to your tires’ potential for multiple • Separations tires. The past few years have seen a retreads as well as sustained operation • Circumferential Breaks decline in the use of tire cages, because in today’s service conditions. of the growing popularity of tubeless • Higher Risk of Road Hazard Underinflation can cause casing tires. Some consider the cage necessary damage and thus diminish the tire’s ability • Loss of Fuel Economy only when inflating the complex as an “air container.” This is of special • Uneven/Irregular Wear assemblies of a tube-type tire and rim. concern since today’s radial tires are • Higher Risk of Road Hazard We strongly recommend using a tire capable of running much longer than • Higher Downtime Expense cage regardless of the wheel or rim type. the life of their original treads. • Loss of Casing Durability The evolution of the radial tire has made it a long wearing, durable component No spare aboard of today’s trucks. We should keep in Add to this fact that many fleets don’t mind that “radial” is not synonymous carry spare tires anymore. Although Check psi weekly with “indestructible”, and that proper fleet inflation pressure maintenance has Paying close attention to inflation inflation is the primary key to preserving improved over the years, sometime over pressures and to tires that have run radial tires’ outstanding qualities. their working life, today’s truck tires are underinflated has never been more still likely to run underinflated or flat. important, considering the potential Continued running this way can for sidewall ruptures, the value of ºseriously damage the casings. retreadable casings, and the cost of Sidewall flexing increases noticeably tire related downtime. when a tire’s inflation drops 15 to 20 The tire industry recommends percent below recommended. Excessive checking inflation pressures once each flexing can result in cord fatigue and week on all tires. This check should be broken cords, and cords adjacent to made with a calibrated tire gauge or a these are subjected to greater tension gauge that is checked periodically with when the tire is reinflated. The potential a gauge known to be accurate. for a sidewall rupture then becomes Another valuable tip is to use a sealing very great. metal or nylon valve cap or a quality Excessive heat does often cause the “air-through” type cap. Plastic caps do liner to wrinkle and discolor, and the not provide a secondary seal to the upper sidewall to visibly distort and outdoor environment, and no cap at discolor. all allows dirt, water and other foreign materials into the valve. Their presence invites air leakage. Carefully inspect any tires that have been repaired or now have cuts, snags or other penetrations. Scrap any that show definite signs of underinflation. Mark a tire that looks suspicious in any way and set it aside for a thorough inspection by a trained tire technician.

41 Inflation S ECTION F IVE

DO’S AND DON’TS FOR MAINTAINING PROPER INFLATION PRESSURE NITROGEN INFLATION DO Over the years, nitrogen inflation has Reduced rim or wheel corrosion has been proposed for various types of tires, also been cited as an advantage of nitrogen • Do maintain proper minimum inflation including large earthmover tires down inflation. However, corrosion is primarily for load carried per the Goodyear through small passenger tires. At the the result of excessive moisture introduced recommended table present time, Goodyear endorses nitrogen by air that has not been properly dried, • Do maintain mated dual tires at inflation for certain sizes of earthmover rather than a direct result of air versus equal inflation tires used in particular applications, and nitrogen inflation. • Do use sealing-type valve caps has issued detailed instructions for these An additional concern is that past • Do check inflation at frequent intervals tires. Anyone concerned with applying studies have shown that a very small or maintaining earthmover tires should percentage of non-nitrogen make-up • Do keep inflation air dry be aware of the Goodyear Service inflation significantly contaminates the Department Bulletins and Off-the-Road contained nitrogen atmosphere within a DON’T Tire Training Manuals that contain details tire. In other words, if any benefits are • Don’t permit tires to operate of nitrogen inflation recommendations to accrue from nitrogen inflation, it is underinflated for these large off-the-road tires. essential that virtually all make-up inflation • Don’t “bleed” air from warm tires The issue of nitrogen inflation for throughout the life of the tire/wheel to relieve pressure buildup over-the-road truck tires is not quite so assembly be diligently controlled to assure clear. Various performance improvements a near 100 percent nitrogen environment. • Don’t reduce tire pressure to obtain have been claimed, including better A final issue is that of insuring against a softer ride treadwear, casing durability, and reduced tire fires and/or self-ignition of tires • Don’t run with one tire of a dual susceptibility to tire fires. resulting from excessive heat. For truck assembly at low pressure or flat Although little actual controlled test tires, this concern has been greatly • Don’t inflate to cold pressures beyond data exists, a summary of Goodyear’s reduced in recent years, primarily rated rim capacity experience with nitrogen inflation for because of the changes from bias to truck tires is the basis for the following radial tires and from tube-type to tubeless comments. Treadwear appears to be tires. The tubeless radial tire is simply affected negligibly by the tire inflation much less susceptible to a tire fire than medium. Specifically, there is little, if a bias tube-type design. This is partly any, tread life change to be expected by because of the simplicity of the tubeless using nitrogen inflation compared to design (i.e. no separate tube and flap to normal air. So far as casing durability create heat from rubbing or internal and retreadability are concerned, the friction when the assembly deflates or primary criteria is to avoid moisture in runs severely underinflated or overloaded), whatever inflation medium is used. To and partly because steel radial truck tires this end, we strongly encourage proper require higher temperatures for a fire to selection of compressor equipment, start than their fabric-reinforced bias-ply air-line routing, the use of air dryers, counterparts. and other good shop practices to avoid In summary, nitrogen inflation the introduction of moisture into high appears to have significant advantages pressure air used for both initial tire for certain sizes and applications of large inflation and make-up air. Again, we off-road tires, especially those operating know of no significantly improved casing in extremely high load or speed durability or retread durability performance environments. However, nitrogen to be expected from nitrogen inflation in inflation appears to have quite small, over-the-road truck tires. perhaps insignificant, advantages for over-the-road truck tires.

42 Total Vehicle S ECTION S IX Alignment

Total Vehicle Alignment

Vehicle alignment settings serve several

purposes in vehicle operation. They affect

handling, steerability, stability and have a

significant impact on tire performance.

Camber settings are not considered

adjustable in the field.

NEVER ATTEMPT TO ADJUST

THESE SETTINGS BY BENDING

OR MODIFYING AXLE/STEERING

MECHANISM COMPONENTS.

43 Total Vehicle Alignment S ECTION S IX

The long treadwear potential offered by modern radial linehaul truck tires can be reduced by the misalignment of tractor and/or trailer wheels and axles. Extensive research has demonstrated that total vehicle alignment programs can pay dividends in extended tire wear and improved fuel economy. Front of Vehicle There has been increased attention to proper truck alignment procedures during the past few years, and for good reason. Current radial steer axle tires provide a much slower rate of wear than earlier generation radial or bias ply tires. This also means that they may reflect the adverse effects of improper alignment Figure 6.1 Toe-in that was unseen on faster wearing tires. Opinions on proper alignment for radial tires often seem as varied as the number of authorities giving them. For this reason, Goodyear has been actively involved in working toward industry wide agreement to define the effects of improper alignment on tire wear, durability and vehicle handling, Front of Vehicle and to establish recommended alignment settings. Much of this work is being directed through industry associations including The Maintenance Council of American Trucking Association, The Society of Automotive Engineers and with individual OEM truck, axle and Figure 6.2 Toe-out suspension manufacturers.

Figure 6.3 Positive camber Figure 6.4 Negative camber

44 Total Vehicle S ECTION S IX Alignment

STEER AXLE LOADED VS UNLOADED ALIGNMENT ALIGNMENT SETTINGS In particular, certain truck and axle The major front-end alignment Alignment changes as load changes, manufacturers have responded to the settings involve: especially steer axle camber, caster and requirements for more precise alignment Toe: toe. Since springs, axles and suspension settings. These OEM’s do not recommend Toe is defined as the difference in mountings vary by truck and components delivery realignment of their vehicles at distance apart, at the front and at the with different weight ratings are often the dealer level. rear, of the steering-axle tires as seen chosen, different unloaded truck Specific irregular wear patterns and in a top view of the truck. Toe-in alignment settings may be required to their causes are discussed in detail in exists when the tires are closer together obtain optimum loaded truck alignments. the “Irregular Wear” section of this in the front than in the rear Figure 6.1 On steer axles, toe and camber settings service manual. and excessive toe-in results in feather are related and should be considered Years ago, alignment meant simply a wear in the direction shown by the together for optimum tire life, especially “front-end job”. But the steer axle is only arrows. Toe-out exists when the tires in line-haul service where treadwear the beginning of the total alignment are closer together in the rear than in rates are slow. Positive camber (refer to story in the radial age. the front Figure 6.2 and excessive toe illustration) creates a slightly shorter We now know that proper attention out results in the feather wear in the rolling radius on the outside shoulder of to drive axles, trailer axles and dolly direction shown by the arrows. a radial tire than on the inside shoulder. axles completes the picture. Not only Camber: This creates a tendency for the tire to does alignment affect tire wear, but the Camber is the tilt of the tires as seen roll toward the outside—a toe-out amount of fuel used by a truck/trailer in a front view of the truck. Positive condition. Since all the working combination as well. (See Section 9 camber exists when the tires are closer tolerances in the tie-rod ends and for additional details). together at the bottom (point of road kingpins must be taken up before contact) Figure 6.3. Negative camber the tendency to toe-out is restrained, exists when the tires are closer together an initial static toe-in setting is essential. at the top Figure 6.4. Caster: Positive caster is provided by a NOTE backward (rotational) tilt of the top Alignment recommendations may of the axle or backward inclination need to be “customized” for certain of the kingpin at the top as seen in vehicle/tire/service conditions. a side view of the truck Figure 6.5. Negative caster would be a corresponding tilt forward at the top. Before any alignment adjustment is performed, always check the vehicle for Figure 6.5 Caster loose kingpins, worn wheel bearings, tie rod ends, or any looseness in the steering system. Adjust wheel bearing end play in accordance with the recommendations of the OE manufacturer. Attempts to correct alignment on a vehicle with worn or loose components are pointless.

45 Total Vehicle Alignment S ECTION S IX

TOE Toe settings generally have the At high values of toe-in or toe-out Camber Wear greatest effect on truck tire treadwear. and at relatively early mileage, the tread One side of thread Toe is also the easiest front-end alignment of the outside or inside ribs can be worn excessively variable to adjust in the shop. completely worn away. For 5/16-inch Road tests were made using three toe-in condition this can occur after trucks with different amounts of loaded only 19,000 miles of highway travel. truck toe-in (1/32-inch, 1/8-inch and Gauges for measuring toe-in setting 1/4-inch) with radial tires on the are relatively simple and inexpensive. steering axles. Every maintenance shop should use The test results showed: them frequently. It is not necessary to •Tire tread mileage decreases with send a truck to an alignment shop to increased toe-in. The 1/32-inch toe-in check toe-in settings. showed the best treadwear rate Setting toe alone is usually not (miles per 32nd of tread depth). sufficient. A total vehicle alignment • Assigning a value of 100 to the (toe and axle) is recommended per Figure 6.6 treadwear rate with 1/32-inch toe-in, TMC RP642. the treadwear rate values compared CASTER as follows: CAMBER Generally, caster is not considered to Loaded After years of recommending camber affect tire wear, but is important in the Toe-in Comparative settings of +1/4 degree for left front and handling and driveability of the vehicle. Value Treadwear 0 degrees for right front, major axle Overall effects of caster can be (Inches) Rates manufacturers have changed to 0 degree summarized as follows: 1/32 100 settings for both left and right steer axle —Too little caster causes: 1/8 82 positions on axles designed for line • Unstable steering 1/4 76 haul service. • Constant corrections required The objective of this change is to •Wander and weave optimize steer tire wear and minimize or • Oversteer In addition to wear, drivers’ reactions • Failure to return to straight ahead to the toe-in settings, without power eliminate irregular wear. Theoretically, these new settings will result in steer out of a turn steering indicated that the 1/4-inch toe-in • Roadwalk caused the truck to “roadwalk” badly. tires running straight down the road in a 0 toe/0 camber mode. Goodyear —Too much caster causes: The 1/32-inch value was considered • Hard steering to have the best handling. Proving Ground tests and independent field tests support this theory. • Shimmy Tire wear due to excessive toe-in on • Road shock radial tires shows up initially as irregular Tires with excessive camber will wear as shown in Figure 6.6. It can be seen Vehicle manufacturers normally wear — more so on the outside than the recommend caster settings for their inside grooves of the tires and more so on that improper camber causes wear on one side of the tire, this can be on the vehicles. Proper caster is that which the right-front than on the left-front tire. gives best handling in combination Excessive toe-out will show a reversed inside or outside of the tire depending on camber setting and tire position with the camber and king pin inclination effect: more wear on the inside than the designed into the axle. outside grooves and more so on the (LF or RF). left-front than the right-front tire.

46 Total Vehicle S ECTION S IX Alignment

ACKERMANN STEERING EFFECT ON TIRE WEAR There are many variables to check (which is the rear axle of a two-axle consider the dynamic effect of many when determining the source of irregular vehicle) to establish a pivot point for outside influences on the path a vehicle tire wear patterns. One potential cause a turn; then drawing lines to the pivot takes through a turn is somewhat correct. for irregular wear on steer tires may be points of the two steer tires. The To further complicate the Ackermann a truck’s “Ackermann” characteristic. Ackermann, then, is the angle the tires/ Principle as it applies to trucks, remember The Ackermann Principle states that wheels needed to be turned to form that the turning axis must be drawn to for any given corner, the outside wheel a right angle with each of the lines determine a pivoting point about which should have less turn angle than the extending from the turning pivot point the vehicle turns. It’s more difficult to inside one, because it is following a to the tire/wheel pivots. This results in define this axis for vehicles with more larger radius than the inside wheel the steer tires “toeing out” when turning. than one drive axle. Fifth wheels, Figure 6.7. A vehicle’s wheelbase is the most critical depending on their location, can also This difference in wheel turning variable affecting the “theoretical alter where this line would fall. angles is determined by the length and Ackermann” for a vehicle. The trend is for vehicle manufacturers angle of the steering arms that are Keep in mind that Ackermann is a to provide different Ackermann arms attached to the hubs of the steer axle. purely geometric concept. The argument for different wheel bases and different The theoretical Ackermann angle that the Ackermann Principle was fleet vocations. for a particular vehicle is determined by developed in the early 1900’s for very drawing a line through the pivoting axis slow-moving vehicles and does not

Ackermann Principle

• Definition The Ackermann Principle States that for Any Given Corner the Outside Wheel Should Have Less Turn Angle Because It Is Running at a Larger Radius than the Inside Wheel.

Figure 6.7

47 Total Vehicle Alignment S ECTION S IX

DRIVE AXLE ALIGNMENT Drive axle alignment is very important. Tandem drive axles that are not parallel to each other have a definite effect on steer-tire wear. Figure 6.8 shows a model of a tandem- drive-axle tractor with both drive axles in proper alignment. In this case, the driver simply steers the truck straight ahead and neither fast wear nor irregular wear would be expected as a result of the driving axles. However, Figure 6.9 is an exaggerated view of a truck with drive axles parallel, but not perpendicular, to the chassis Figure 6.8 centerline. The eight driving tires create a “thrust angle” to the left at the rear of the truck. Turning the steering wheel slightly to the left aligns the steer and drive tires to run parallel, but the vehicle however will “dog track.” Even though lateral forces on the steer tires are minimal, the steering geometry is affected, which may result in asymmetrical steer tire wear. A more severe case is shown in Figure 6.10. Here the drive axles are neither parallel to each other nor perpendicular to the chassis centerline. The drive-axle tires are trying to force the vehicle to turn left and the driver must compensate by turning to the right. This will result in fast and irregular wear Figure 6.9 and, as recent tests have shown, in a much more severe way than the previous case. These tests also indicated that the steer tire on the same side of the truck on which the drive tires are closest together will wear into an out-of-round condition as well. Recommendations for drive-axle alignment are as follows: •Tandem axles should be parallel within 1/8-inch difference between the axles centers measured on the left and the right side of the vehicle. Figure 6.11 •Axles should be perpendicular to the chassis centerline within 1/8- inch Figure 6.10 measured between axle end and vehicle centerline. Figure 6.12

48 Total Vehicle S ECTION S IX Alignment

TRAILER AXLE ALIGNMENT With more long-wearing radial tires The loaded axle camber can be up The following guidelines have proved being applied to trailer axles, their to negative 1° without affecting to be beneficial for improving overall alignment has become an important issue. tire wear. tire treadwear: Trailer-axle tires have the potential for Axles should be parallel to each other longer life (more miles per thirty-second STEER AXLES within 1/8-inch measured between inch of treadwear) than any of the tires on TOE IN (unloaded): axles on both sides of the trailer at the tractor. They are, therefore, more Check Limits* 1/16'' ± 1/16'' a 71.5-inch axle track. This provides susceptible to irregular wear due (Range 0-1/8'') a scrub angle of ±0.1°. to misalignment than any other tires on Reset Limits 1/16'' ± 1/32'' the vehicle. Axles should be perpendicular to the *When alignments are found within Goodyear’s recommendations for centerline of the trailer frame within these limits, adjustment is not trailer alignment are as follows: 1/8-inch per side or 1/4-inch from necessary. If outside of check lim- side to side at a 71.5-inch axle track. its, set to the reset limits. Preferred toe setting: This provides a thrust angle of ±0.2°. DRIVE AXLES 1/32-inch toe-in to 1/32-inch Tandem axles to be parallel within toe-out, or ±2.7 minutes per spindle. 1/8'' measured at axle end. Acceptable toe setting: 1/16-inch toe-in to 1/16-inch toe-out, Axles to be perpendicular to chassis or ±5.4 minutes per spindle. centerline within 1/8'' when measured IN-SERVICE from axle end to chassis centerline, ALIGNMENT or within 1/4'' when measured from •Rear Tandem Parallelism RECOMMENDATIONS left to right axle end. Toe-in is recognized throughout the TRAILER AXLES industry as the most important contributor Tandem axles to be parallel within to optimizing steer tire treadwear. In 1/8'' measured at axle end. order of priority, gains in tread life can ABbe expected by focusing on the Axles to be perpendicular to chassis following vehicle alignment parameters: centerline within 1/8'' when measured • TOE from axle end to chassis centerline, • REAR TANDEM PARALLELISM or within 1/4'' when measured from • CAMBER (NON-ADJUSTABLE) left to right axle end. Nominal toe setting: A = B within 1/8 inch • REAR TANDEM PERPENDICULARITY • CASTER 0'' ± 1/32'' Figure 6.11 Most vehicle manufacturers, in recent years, have developed new factory •Rear Tandem Perpendicularity equipment and procedures to control alignment to much narrower tolerances than was previously possible. Today there is less need to adjust alignment ABon new vehicles than in the past. Alignment accuracy and repeatability can best be achieved by proper training, adherence to strict procedures and by properly maintaining and frequently Reference TMC Recommended calibrating alignment equipment. Practice RP642 regarding total vehicle THE VEHICLE MANUFACTURER’S alignment for more detailed information. ALIGNMENT SPECIFICATIONS A = B within 1/4 inch SHOULD BE ADHERED TO.

Figure 6.12

49 Factors Affecting Treadwear S ECTION S EVEN

Factors Affecting Treadwear

Alignment problems are often blamed for all

irregular treadwear. However, many other

factors can be responsible for, or contribute

to, irregular wear. While the wear pattern

can often suggest the cause of the problem,

it sometimes takes real detective work to

track down and correct the real source

of trouble.

50 Factors Affecting S ECTION S EVEN Treadwear

Footprint Shapes

ALIGNMENT

DUAL MATCHING

Bias Radial INFLATION Figure 7.1 A bias tire footprint is oval shaped… the radial footprint is rectangular.

BALANCING

TIRE SELECTION

The issue of irregular tire wear has in bias ply tires. Since the tread wears always been a concern even in the days away usually much faster on bias tires, when most trucks ran bias ply tires. With unusual wear patterns are literally today’s longer wearing radial tires, scrubbed off as they develop. irregular wear has surfaced as the primary The Technology & Maintenance concern of most truck maintenance Council (TMC) of the American managers. In fact, it is the ability of today’s Trucking Association has publicly said advanced radial tires to deliver long that the positive attributes of the radial original tread life which requires even tire, particularly longer tread life, Figure 7.2 Radial Tire Conditions Analysis Guide more attention to good maintenance can result in the tire exhibiting more — an excellent reference book. practices and vehicle alignment. irregular wear patterns when vehicle and Radial tires have a different footprint tire maintenance or tire construction shape than bias tires. See Figure 7.1. is inadequate. This results in less scrubbing and longer The TMC has also published an tread life. However, this same attribute excellent reference guide titled Radial Tire of the radial design can also result in the Conditions Analysis Guide. This booklet tire exhibiting more irregular wear when clearly defines the types of irregular wear vehicle and tire maintenance are below common to steer, drive, and trailer axles par. These wear patterns are not as evident and offers possible reasons that such wear occurs. Figure 7.2. Contact The Technolgy & Maintenance Council at http://tmc. truckline.com or order publications through The ATA Marketplace: 1-800-282-5463.

51 Factors Affecting Treadwear S ECTION S EVEN

STEER TIRE WEAR Uneven or irregular tire wear is a While many fleet owners and widespread problem in today’s trucking maintenance personnel believe they KEY IRREGULAR industry. All brands of rib tires have have heavily loaded steer axle applications, WEAR CONDITIONS experienced this undesirable situation. they’re running with loads in the 10,000 DEFINED Extensive testing has proven that to 10,500 pound range and below. Heavy Chamfer wear — A nibbling or vehicles with lightly loaded front axles GVW doesn’t equate with heavy front erosion that occurs on the outside are more prone to irregular steer tire wear axle load. edge of the shoulder ribs of a tire. than those with heavily loaded front This condition typically results ends Figure 7.3. By lightly loaded, we’re Load/Footprint Comparison from slow rate of wear line-haul talking about a front axle configuration service and does not indicate a tire of 10,000 to 10,500 pounds or less for or vehicle problem. the typical linehaul-sized tires. We also know that tractors with wheelbases more Erosion or river wear — A nibbling than 200 to 210 inches long are also effect at the edge of the interior candidates for irregular steer tire wear. ribs of a tread design. It’s most often Several factors help determine steer tire seen on very slow wearing tires in load. These include vehicle configuration, Figure 7.3 line-haul steer applications. wheelbase, axle set-back and fifth wheel Fast rib wear — One or more of position. How this load contacts the Tire inflation also plays a role in tire the interior ribs of a tire wear away road surface is then influenced by wear. Once loading is determined, you much more rapidly than the alignment settings. Vehicle toe, camber, must run your tires at the proper inflation adjacent ribs. Tire construction, caster, drive axle parallelism and to match loading. Your tire company itself, may be the cause. perpendicularity are important factors representative should help you determine in steer tire wear patterns. optimum inflation for that configuration. Diagonal wear — Rapid wearing All things considered, how a tire A good rule of thumb — inflate to away of a diagonal patch of the tread wears depends on the forces that the T & RA recommended pressure tread design. Causes are generally act upon the contact patch of that tire required for the load plus 10 psi. This non-tire related. Probable suspects as it meets the road. will compensate for tire-to-tire variations include mismounting a tire on the If a tire is highly loaded, it tends and normal leakage. wheel, brake or bearing problems. to have a square footprint shape. The Periodic inspections of your vehicle Diagonal tire wear is not caused shoulder rib contact area is very long, and tires are a must. Look for signs of by a heavy splice or component about the same length as the center ribs. irregular wear or vehicle component ending in a tire. As the tire rotates, contact with the road problems. Then take immediate action Fast shoulder wear — Rapid is good. to correct these problems. wearing away of one or both tire By contrast, a lightly loaded tire tends And finally, work very closely with shoulders on steer axle position. to have very short shoulder ribs, much your tire company representative to The problem shows up as smooth shorter than the center rib. As this tire determine the right tire for the application. rapid wear or a scalloped “island rotates, the footprint center maintains A tire designed for highway use, for wear” configuration as the tire runs. very good contact but the shoulder example, may not be the best choice for area does not. This causes much more running off-road. Tires, like trucks, are scrubbing action and wearing away of built to do specific jobs. Defining that the shoulder rib. mission is a good first step. Vehicle misalignment, non-parallel or non-perpendicular drive axles and suspension system problems naturally affect steer tire wear.

52 Factors Affecting S ECTION S EVEN Treadwear

SETBACK STEER AXLES Though increasingly popular today, Tires on the “super setbacks” must work Loaded vs. unloaded alignment angles “setback” steer axles are not new to the harder, and in some cases, require higher Differences in payload can also affect trucking industry. For many years, “setback” inflation pressures to support the increased steer tire loading differently, depending front axles have been used in on/off road loads. Load/inflation pressure tables are on fifth wheel location, suspension type applications in construction, oil field, available from www.goodyear.com/truck, and degree of axle setback. Therefore, waste hauling and specialized services. Engineering Data Book or Over-the-Road you can’t continue to assume traditional The primary benefits of “setback” Truck Tires, or a qualified tire company changes in toe, camber and caster from steer axles are improved maneuverability, representative. bobtail condition (typical when checking more desirable load distribution and, in If higher steer tire pressures are alignment) to fully loaded. In fact, certain many cases, improved ride. The application required, this may mean you’ll be using “setback” axle designs have shown no of “setbacks” to over-the-road linehaul different inflation pressures for drive camber change. type trucks, however, is fairly recent. and trail tires. Toe change, on the other hand, can The term “setback” is relative, and range from no change to a decrease, or, Increased lateral tire scrub some designs are more setback than others. in some cases, to an increase with addi- As the wheelbase dimension shortens, Generally, the axle of a modern “setback” tional load. Caster change may also be steer tires must generate an increasing linehaul tractor is positioned about 13 to different from model to model, since amount of side force to turn the truck 15 inches behind its traditional position. most “setback” axle designs also employ chassis when cornering. This is especially This design is typically found on long springs that are longer or have different true for tandem drive axle units. As conventional and medium conventional deflection characteristics. an example, compare a tractor with a cab models. 140-inch wheelbase with one whose Ackermann steering geometry More pronounced “super setbacks” are wheelbase is 230 inches Figure 7.4. While Ackermann geometry has not usually found on COE models where the Steer tires on the shorter vehicle must typically been a major problem on axle is positioned about 25 inches behind generate 65 percent more cornering linehaul type vehicles, it should now be its normal position. Collectively, all trucks force to slide the tandems around a considered because most “setback” axle with “setback” axles can be expected to designs also incorporate increased present distinct characteristics which can wheel cut angles. The industry standard affect tire selection and usage patterns. Truck Wheelbase Effects for many years has been in the 32- to These include shorter wheelbases, higher on Steer Tire Wear 34-degree range. Now typically in steer tire loads, higher wheel cut angles. new designs are wheel cuts of 42 to 44 While these characteristics are “setback” degrees, meaning steer tires are likely to steer axle benefits, there are others that be scrubbed more severely when turning. can adversely affect tire wear. 230 As a result, the effects of improper or 140 Steer tire inflation pressures compromised Ackermann geometry will As a general rule, irregular wear be more pronounced. tendencies are more of a problem on Suspension damping control trucks with lightly loaded steer axles. Damping control has also become This is especially true of trucks pulling Shorter wheelbase truck must develop more more important, since many “setback” heavy loads where high drawbar force cornering force with steer tires to generate axle designs employ softer riding on the kingpin tends to unload the steer the same cornering moment to turn truck or to counteract a chassis thrust angle suspensions. The older stacked spring axle when the truck is rolling. Rearward designs had considerable leaf-to-leaf positioned fifth wheels offer further Figure 7.4 friction, which tended to act as a built-in opportunities to reduce steer axle loads. shock absorber. This damping also varied “Setback” axle trucks tend to have corner. The normal result will be faster with loading. heavier steer tire loading both statically overall steer tire wear rates than Now, depending on the specific and dynamically. This is because most of experienced by the longer wheelbase suspension, damping control can become them also employ extensive aerodynamic unit. Another result will be less irregular critical. Shock absorbers should be packages that restrict fifth wheel placement wear because the extra scrubbing tends properly sized, maintained and replaced flexibility. In fact, some “super setback” to clean up uneven wear patterns as they when necessary to control suspension designs can have nearly identical steer develop. You’ll also find tires with wider movement, which, in turn, leads to tire tire loadings from bobtail to fully treads or more massive tread rib designs wear irregularities. loaded condition. will usually perform better on the shorter wheelbase vehicles. 53 Factors Affecting Treadwear S ECTION S EVEN

DRIVE TIRES Let’s review some of the key elements that impact drive tire wear: Engine Torque (More usable torque means less tread life) Engine torque is measured in foot- pounds of twisting force without regard to time. Peak torque on many of today’s engines occurs at lower engine rpms and remains at a relatively high level over a wide rpm range. A typical engine might develop 1,200 to 1,250 foot-pounds of peak torque at only 1,300 rpms. High engine torque over a wide rpm range adversely affects drive tires, which transmit this higher torque to the highway. Increased stress, deflection, deformation and reduced tread life result. Highway Speeds (Faster speeds mean less tread life) Linehaul tractor trailers are now permitted to travel at 65 mph in rural But tighter turns equate to higher Extreme variations in air pressures of areas in place of 55 mph in 71 percent cornering forces in the drive tire footprint dual wheel assemblies is another major of the states. At 65 mph, that means a and reduced tread life. Depending on the cause of reduced tread life and also of 16-percent tread life penalty, according percentage of straight-ahead highway irregular drive tire treadwear. Fleets that to one study. Experts cite as causes driving, these forces can also cause rear don’t control air pressures of duals in increased tire footprint deformation and tandems to wear much faster than effect allow the tire with lower air pressure higher tire running temperatures. forward tandems. to overdeflect, deform, scrub excessively and non-uniformly and eventually develop Rear Suspensions Inexperienced Drivers irregular drive tire wear. (Service/maintenance sensitive) (Tread life can suffer) Here are some tips to obtaining Good suspension and shock High turnover means truckload and desirable drive tire tread life with minimum maintenance is critical to obtain long irregular route drivers are less experienced irregular wear: than in the past. Driver turnover surpasses tread life and uniform wear. Inadequate • Recognize the effect of vehicles, 100 percent annually in some fleets. care can cause uncontrolled jounce and service and operating conditions Inexperienced drivers can abuse their rebound, and over long time periods, on drive tire tread life. vehicles with rough gear shifting, irregular drive tire wear as well. •Train drivers in proper operating spinning wheels on wet surfaces and Empty backhauls can aggravate the techniques. fast accelerating and braking. problem. Lightly loaded trucks with leaf spring suspensions and deep tread tires • Exercise speed control. Setback Steer Axles can develop a cyclic bouncing process, •Maintain rear axle/tandem alignment. (Affect drive tire wear) particularly on rutted or deteriorating • Balance air pressure between duals. Setback steer axles were engineered to highways and highly crowned roads. improve vehicle comfort, load distribution Significant tread life losses and various and vehicle maneuverability. A tractor’s degrees of irregular wear can result. wheelbase is shorter when its steer axle is placed 13 to 15 inches behind the usual position (or up to 25 inches in the case of super setback axles). Shorter wheelbases mean greater wheel cut angles, from the normal 30 degrees up to 42 inches in some cases. Smaller turning radii are the result of higher cut angles.

54 Factors Affecting S ECTION S EVEN Treadwear

Suspension systems are changing. Early trucks were stiffly sprung with Leaf Springs SHOCK ABSORBERS — suspensions similar to horse-drawn 3 CONSIDERATIONS buggies. Today, the demand is for a • Selection. For maximum softer ride. Better driver and passenger effectiveness, select the right comfort is one reason. Another is a shock absorber for the job. need to protect delicate cargo such as Consult with a manufacturer’s electronic equipment and computers. For Stacked Multiple Leaves representative to make the these and other reasons, air suspensions (Much Leaf to Leaf Friction) proper choice. are becoming more popular. • Placement. Proper placement There are two basic suspension of shock absorbers in a systems. A taper leaf is used primarily suspension system ensures on steer axles and trailer axles. Air optimum shock compression suspensions are used mainly on drive or extension and axle Taper Leaf movement damping. axles and trailer axles, but are now (Little Leaf to Leaf Friction) being introduced on steer axles. Besides • Maintenance. Regularly check shock absorbers to make sure a softer ride, air suspensions provide full Figure 7.5 Taper-Leaf springs produce little self-dampening. suspension movement regardless of load they are performing adequately. Replace shocks when they condition and the ability to equalize the Temperature is another way to check are worn. load between axles. Radial tires work shock effectiveness. After a truck returns best when in firm contact with the from a highway run, a mechanic should road surface. touch the shock absorber. A warm shock Suspension systems are a combination is working, a cold shock is not. BEARING ADJUSTMENT of springs and dampers (shock absorbers). With air suspensions, shock absorbers Ask five different fleet maintenance Older, multiple-leaf spring suspensions had are also considered the “stops” at the managers about how wheel bearing so much leaf-to-leaf friction that they were extended end of the suspension travel. adjustments affect alignment settings and virtually self-damping Figure 7.5. Today’s Present and future trucks will have you’re likely to get five different answers. taper-leaf systems, with fewer leaves and softer, more compliant suspensions that They’ll likely agree that axle end play is space between leaves, produce little self- provide many advantages over older a tire wear concern but the reasons why damping. In fact, a low friction material systems. Proper maintenance of these may not be fully understood. often is placed between the leaves to reduce suspensions will assure the benefits of Axle end play is an indicator of damping. Air bags also lack self-damping. these systems are realized without a wheel bearing adjustment. End play is the Placement of shocks in the suspension negative impact on tire life. movement, in and out, of the tire/wheel/ system can help or hinder their effectiveness. Vehicles should be spec’d considering hub assembly at the end of the axle. Most Consider, for example, shocks mounted ride and tirewear. Frequent suspension vehicle and axle manufacturers say near the center of the frame. Bump inputs system maintenance assures maximum .001-inch to .005-inch end play is to both the right and left sides of the axle treadwear and tire life. acceptable. Trailer manufacturers may – such as road expansion joints – are allow up to .020 inch. You need a dial properly damped. But a bump input to indicator to measure this movement one side or the other results in the axle accurately, but experienced mechanics rotating about its center. There is little and technicians can grab the tire at two shock compression or extension and little points 180 degrees apart and detect damping of axle movement. in-and-out movement by giving the Fluid leaks around the shock’s piston assembly a wiggle. Not a precise rod are a sign that shocks should be measurement by any means, but replaced. Replace a shock absorber if experienced hands can usually tell one end is disconnected or if the shock if there is too much play, flagging can be easily compressed and extended. the need for maintenance.

55 Factors Affecting Treadwear S ECTION S EVEN

Axle end play changes camber and A .020-inch end play will only change toe properly so irregular tire wear will be toe setting. For example, pushing in the the camber about 1/8 of a degree. Camber chronic if end play is not within spec. top of the assembly and pulling out at the tolerance is commonly plus or minus 1/4 Some experienced mechanics claim bottom will change camber angle. Similarly, of a degree, so if end play is kept within improved tire and bearing life with pushing on the front side of the tire spec, the camber change caused by this “preloaded” bearings. In addition, some while pulling on the rear alters toe setting, amount of play is insignificant. long-life, low maintenance wheel systems which raises the obvious question: “How But tolerances are closer for toe. Toe are being offered that require a preloaded much change in camber and toe does setting is commonly expressed as the bearing arrangement as part of their wheel bearing end play cause?” difference in distance from the tractor standard installation requirements. To The amount of change can be center line to the front and rear edge avoid overtorquing these systems, a great predicted with mathematical calculations. of each tire as measured at hub center deal of care must be used to achieve a The graph in Figure 7.6 shows height. Recommended settings for proper bearing preload. As a result, the camber change for a given amount of over-the-road trucks are: manufacturer’s recommendations should end play. Steer axles: be closely followed. Toe in 1/16'' ± 1/32'' (unloaded) Bearing manufacturers strongly End Play vs. Camber For trailer axles: discourage overtorquing a bearing just to 0 ± 1/32'' eliminate servicing after a break-in period. .020 We also calculated possible toe-in Although you get more bearing and tire

.015 change at various end play settings. wear, a too-loose bearing is safer on an Remember, toe in is the relationship over-the-road truck than a too-tight one: .010 between front and rear sides of one tire, the overtorqued bearing can heat up, Max. Recommended By

End Play (in) Most Manufacturers so we can look at toe change due to end may crack and could cause a dangerous .005 play on one side or both sides of the axle failure on the road. 0.02.04.06 .08 .10 .12 vehicle. The graph in Figure 7.7 illus- We urge you to limit axle end play Total Camber Change (˚) trates our findings. to the low end of the specified tolerance Figure 7.6 End Play vs. Toe Change range and follow the manufacturer’s or Camber Change recommendations when preload is If end play and bearing taper angle required. Make periodic end play checks are known, calculations may be used to when permitted by the manufacturer to determine the diametral clearance (DC) maintain tight settings. The payoff will of both inner and outer bearings. Then, be more accurate toe adjustment, safer knowing the distance between the bearings, operation and longer tire life, particularly the angle change is found using the for high mileage radials. following formula: 1/2 DC (Inner Bearings) x 1/2 DC (Outer Bearing) ENVIRONMENTAL Distance between bearings EFFECTS Figure 7.7 Road surfaces and environmental factors play a big factor in tire performance If both sides of the steer axle are at and tread life. An understanding of the maximum allowable end play, toe change effect pavement conditions have on End Play of .080 (more than 1/16) inch could treadwear can help fleet managers analyze vs. Toe result. That’s a very significant difference variables in overall tire costs. Engineering Change because maximum allowable toe tolerance studies have drawn conclusions about or is only 1/32-inch. So you should keep the following variables: Camber end play on steer axles well below Change accepted maximums to get longest tire life. Road surface textures on treadwear Maintain within specs for longer tire Tire engineers agree that rough, sharp wear. Obviously, any tire/wheel/ hub surfaces and those with embedded shells assemblies that are outside the current are more abrasive and tend to generate spec for axle end play have potential for faster wear rates than polished concrete and tire wear problems. And they won’t go smooth asphalt. Rough surfaces create a away. Excessive end play prevents setting higher scrub force, which accelerates

56 Factors Affecting S ECTION S EVEN Treadwear

treadwear. (Tests show coarse chip and Curves and tread life Also affected directly is tire performance. seal pavement increased rolling resistance More curves, lower tread life. That’s The faster you roll, the more heat by 33 percent over concrete.) because curve-imposed side forces cause your tire casing creates. This degrades To illustrate, engineers have designed lateral tire deflection and deformation. casing durability, promotes irregular indoor laboratory tests and imposed Tests show frictional forces during specific treadwear, shortens tread life and extreme conditions on sets of similar cornering can be 5.8 times as great as reduces impact resistance. tires. In one specific example, they found when driving straight. During braking, Casing durability: The extra heat abrasive surfaces can create a 100 percent frictional forces can be 2.4 times as great. associated with running faster will affect worn situation in as little as 1,000 miles. your tire casings over time. If you’re Climate and tire wear Meanwhile, the same tires evaluated on currently averaging two retreads per Water acts as a lubricant. Tires that polished/ worn surfaces typically were casing, you may only average 1.5 to 1.75 often travel over wet pavements can only 25 percent worn after 2,000 miles. retreads per casing by running at higher show up to 30 percent longer treadwear While far from real road conditions, the speed limits. than tires that run only on dry pavements. tests showed a wear rating improvement Running hotter can take its toll on Temperature is also a factor. When the for the smooth surfaces of 800 percent. rubber. A good example is in the tire’s temperature increases, so do treadwear Under actual conditions, the tires would shoulder area, where the belt edge of the rates. For example, when roads are wet, have run much farther in both cases. top steel belt can obtain temperatures up fleets typically obtain better treadwear Fresh concrete is tough on tires. In to 180 degrees F running continuously in the fall and winter verses spring outdoor tests, engineers found treadwear at 75 mph. At 55 mph, belt edge and summer. rates were 70 percent faster on month-old temperatures average 160 degrees F. Driving technique plays a major role pavement than on 24-month-old concrete. The increased temperature degrades in maximizing tire life, but so does Reason: Over time, traffic wears down the casing durability, especially in the where the vehicle is driven. abrasive edges of the fresh surface. second and third retread stages. If we were to assign wear ratings to Accelerated Treadwear: Tests show several different road surface materials, HOW SPEED AFFECTS that every 1 mph increase over 55 mph the differences would be significant. IRE EAR results in 1 percent reduction in tread Dirt, for example, would rate approxi- T W mileage. So, running at 75 mph instead mately 50 while hot mix asphalt would In 1995, Congress repealed the of 55 may cost your fleet 20 percent in score 100. Higher numbers indicate national 55 mph maximum speed limit. removal miles. treadwear mileage. By early summer 1996, 10 states had Irregular wear: As your truck speed raised the truck limit to 75 mph, seven increases, your tires flex more, resulting in others to 70 mph and 22 states to 65. Road Surface Wear Rating a different footprint. Going from 55 to 75 If you’re running where 75 mph signs mph causes the tread centerline to lengthen, Hot mix asphalt 100 are found, you might shave two hours which can cause tire shoulders to develop Concrete 90 from a 500-mile trip. That assumes no cupping and overall fast shoulder wear. Crushed rock asphalt 65 extra rest stops, no construction slowdowns Impact resistance: Your tire’s resistance Dirt 50 or any slowdowns at all. But surveys show to sidewall snags and tread area punctures that faster drivers take more breaks due is reduced at higher running speeds to stress, refuel more often, suffer more because of higher rubber temperatures. Grades and tire wear breakdowns and expose themselves to Expect more incidents of road damage Today’s high torque/low rpm diesel more potential accidents. at higher speeds. engines have changed typical driving Conclusion: a faster 20 mph speed How can truckers minimize these techniques for truckers from “slow uphill/ does not often translate into a 20 mph negative factors? Be sure to maintain fast downhill” to more constant speeds. But faster average over the long haul. proper air inflation pressure. Running this added torque to the drive wheels has And what does rolling in the fast lane underinflated will accelerate all the also created greater driveline and tire stress do to your rig? problems associated with higher speeds. over extended time periods. Steep grades First, there is the fuel penalty. The rule themselves add to this stress.The two factors of thumb says for every 1 mph over 55, subject tires to higher longitudinal forces your semi’s fuel economy goes down by in the tire footprint area. This condition 0.1 mpg. So, running 75 instead of 55 leads to tire slip, abrasion and wear. may cost you 2 mpg, or 33 percent if Those carriers operating in the your truck averages 6 mpg. mountains, for instance, can experience Even running 65 mph vs. 55 costs you 50 percent faster treadwear than carriers 1 mpg or an extra 2.5 cents per mile. operating on relatively flat terrain. 57 Ride Disturbance S ECTION E IGHT

Ride Disturbance

Vibration in modern over-the-road trucks

can affect driver comfort (and, therefore,

productivity), cargo safety, and equipment

wear. As with most other problems, vibration

can have a number of different sources and

an effective solution requires that the cause

(or causes) be accurately determined.

58 Ride S ECTION E IGHT Disturbance

Frame Flexing/ Resonance

Figure 8.2 Frame flexing may occur at a point that causes great discomfort for the driver. four remaining ones. The driveline, of course, must be balanced, but may also cause a problem if the angle that the driveshaft forms between the back of the transmission and the front of the Concern for truck vibration problems Additionally, longer wheelbase trucks differential is too great. See Figure 8.3. has increased in recent years as trucks are more likely to have a frame flexing or This is encountered most frequently with have evolved to fill today’s more demanding resonance problem. This simply means a short wheelbase vehicle, such as a single trucking industry needs. Several current that as the frame flexes (as all frames do drive axle tractor, designed to pull design trends (e.g. longer wheel bases) to some degree), the amplitude of flexing multiple trailers, or with a truck chassis have resulted in trucks that are more and the locations of the high and low that has been shortened. Specific susceptible to vibration problems. points along the frame are more likely to procedures and specifications for For increased driver comfort and be objectionable on a long wheelbase checking driveline angularity can be reduced cargo damage, many over-the-road chassis. See Figure 8.2. found in truck service manuals for the suspension systems are now designed Whenever a vibration complaint is particular make/model of the vehicle to be “softer” than in the past. This is voiced on a particular vehicle, the first being diagnosed or from driveline accomplished in part by having springs step is to eliminate the non-tire sources equipment manufacturers. Any ride or other devices that have more vertical and concentrate on the remaining disturbance that can be eliminated by travel (referred to as jounce and rebound) possible offenders. taking the truck out of gear at road speed when a bump is encountered. Since little can be done about road is probably engine or driveline related. Some frequently encountered sources roughness, we must concentrate on the of ride vibration disturbances are: Road surface roughness Driver Ride Tire/Wheel/Hub non-uniformity Excitation Sources Judgement Driveline component balance or propshaft angularity/phasing 1. Road Roughness 2. Tire/Wheel/Hub Improper fifth wheel position Truck’s Cab Trailer influence 3. Driveline Balance Dynamic Vibrations 4. Fifth Wheel Position Response 5. Trailer Influence

Figure 8.1 Frame Flexing/Resonance

59 Ride Disturbance S ECTION E IGHT

Fifth wheel position and trailer • TYPE OF DISTURBANCE ALANCE ELATED influences can often be altered to – Up and down indicates run-out, B R determine their effects on a ride vibration balance VIBRATION concern. If the problem seems to be – Side to side indicates run-out, Balance is most critical on free-rolling related to the tires, wheels, or rims or balance and possibly irregular wear wheels (steer and trailer). In general, hubs, you should consult your tire – Steering wheel shimmy indicates spin-balancing of drive tires is not needed. company representative. steer tire dynamic imbalance It can also be dangerous due to the If ride testing determines that the differential action, which can result in vibration is likely due to rotating axle very high rotational speeds at one axle components, guidelines for pinpointing RIDE DIAGNOSTICS: end, and damage to the truck is possible. tire/wheel/hub related vibration problems TIRES/WHEELS On-vehicle balancing with a properly calibrated spin balancer may aid in are as follows: • Identify critical conditions/speed of correcting the vibration problem by the vibration balancing that particular tire/ wheel •A vibration that gets worse as speed or rim/hub assembly. However, when RIDE TEST TIPS increases may be balance related placing that tire and wheel (or rim) • Drive 15-20 miles to warm up tires and •A vibration that occurs at only one on another wheel position or vehicle, eliminate flat spotting which occurs speed is probably run-out related it is likely to be out-of-balance. If the when a truck has been sitting idle. •A vibration that phases in and out problem is an out-of-balance hub, • LOCATION – STEERING indicates a problem at more than the ultimate solution is to have the WHEEL, SEAT one wheel position hub balanced. –Steering wheel and/or floor under • Low speed wobble is run-out related – the driver’s feet – indicates steer tires not a balance problem – Backslap in seat – indicates rear •A vibration while braking only is UN UT ELATED assemblies R -O R probably a brake system issue VIBRATION For run-out problems, the match- Driveline Angularity mounting procedure is a complex but effective method to eliminate, or at least 1 isolate, the source of the concern. Match- 2 mounting isolates the tire, wheel, and bolt circle of the wheel to determine 31 where the problem may be. It can also determine if a combination of variables is responsible because the tolerances “stack” 1 Universal Joint to create an unacceptable condition. 2 Slip Joint Since all tires and wheels are likely to 3 Shaft have some run-out and all bolt circles are not perfectly centered, it is important Figure 8.3 Driveline angularity can cause vibration problems. that these factors do not “add up” to create a ride vibration even when individual components are within spec. The accepted Runout Guidelines guidelines for run-out of tires, wheels, Radial Lateral and wheel bolt circles are shown in Figure 8.4. Vehicles with assemblies Assembly (on vehicle) .060'' .150'' and components within these guidelines Sensitive Vehicle <.060'' should not have vibration problems due Wheel .040'' to tire/wheel factors. Bolt Circle .020'' If run-out appears to be a problem, use Tire .060'' .080'' the following match-mounting procedure to attempt a correction: Figure 8.4

60 Ride S ECTION E IGHT Disturbance

MEASURING RADIAL RUN-OUT High Spot High Spot Assembly Wheel Index

Low Spot Run-out is a measure of deviation • Measure radial run-out on the • Mount the tire/wheel assembly from a perfect circle 1 3 vehicle at the tire centerline on a balancer. Check tire “GG” grooves for concentricity with •Warm up tires rim flanges on both sides (visual). • Lift vehicle If not concentric, deflate, break • Place the dial indicator against the sidewalls away from rim flanges, center of the tread pattern High Spot Wheel lubricate and re-inflate •Turn the wheel slowly and watch the Assembly Index • Recheck the run-out on the needle Hub balancer. Compare peak locations • Find the low spot and zero the gauge Index and magnitudes to results from • Spin the wheel to check run-out on-vehicle measurement. Mark • Mark the high spot the high spot of the assembly and •A reading of less than 0.060” (RRO) is index the tire to wheel as shown usually good. Sensitive vehicles may Assembly • If RRO on balancer is greater than require 0.060” or less Position RF on vehicle, hub-to-wheel index is Right Front OK. If RRO is less than on vehicle, REQUIRED TOOLS hub index should be rotated 180° 2 • Mark the high spot of the when the assembly is reinstalled • Goodyear infoLink, tire/wheel assembly and the on the truck Ph: 800-755-2772 amount of run-out if over .060” – Gauge (0.100" per rev) & slider • Index tires to wheels and wheels to shoe, part no. 220-011-300 hubs and record assembly position (LF, RF, etc.) on each tire before – Stand, part no. 220-011-200 removal from vehicle

61 Ride Disturbance S ECTION E IGHT

Wheel Wheel New Assembly Index Index High Spot

First Assembly High Spot First Assembly RF High Spot

4 • If the assembly RRO is over 0.060”, 6 • If above step is OK and the run-out 8 • Remount tire on the vehicle and rotate tire 180° on wheel and is still unacceptable, and the new measure radial run-out. Run-out remeasure on balancer. If OK, stop. high spot is within 6” of the wheel should be the same as measured If still excessive, rotate 90° and index, replace the wheel. (i.e., If the on the balancer. If out of limits, remeasure. If OK, stop and balance. high spot moves with the wheel, check the stud circle run-out the wheel’s run-out contribution is • When re-installing steer assemblies higher than the tire’s contribution) on vehicle and before tightening lug nuts, locate the high RRO spot at 12:00 on the hubs Wheel • When re-installing drive dual Index 7 • Mark final assembly high spot assemblies on vehicle, install (red) from inside to outside of tire, highest RRO spot of one assembly so it is visible for mounting on the at 12:00 on the hub. The high New Assembly truck. Erase original marks on the spot of RRO on the other assembly High Spot tire (yellow) should be opposite (180° from) • Balance all assemblies before the first assembly replacing on vehicle • Torque all lug nuts to manufacturer’s First Assembly • Repeat steps 1-6 for each assembly specification and re-ride the truck High Spot on vehicle to optimize overall vehicle ride 5 • If the run-out is still unacceptable and the new high spot is within 6” of the first high spot on the tire, replace the tire. (i.e., If the high spot moves with the tire, the tire’s run-out contribution is higher than the wheel’s contribution) For further information, see TMC Recommended Practice RP648 regarding ride troubleshooting.

62 Factors Affecting Truck S ECTION N INE Fuel Economy

Factors Affecting Truck Fuel Economy

63 Factors Affecting Truck Fuel Economy S ECTION N INE

VEHICLE AND ENGINE DESIGN A. Performance Factors Fuel consumption is a function of FIGURE 1 power required at the wheels and overall Vehicle Speed engine-accessories-driveline efficiency. vs. Factors that affect fuel consumption Aerodynamic Drag and Tire Drag at steady speeds over level terrain are: Power Output-Engine-Accessory- Driveline System 1. Basic engine characteristics; fuel Drag Force consumption vs. RPM and BHP. Aerodynamic Drag 2. Overall transmission and drive axle gear ratios. Tire Drag 3. Power train loss; frictional losses in overall gear reduction system. 4. Power losses due to fan, alternator, air-conditioning, power steering, and 30 40 50 60 70 80 any other engine-driven accessories. Vehicle Speed Power Required - Vehicle and Tires The horsepower required for a vehicle to sustain a given speed is a function of B. Type of Vehicle Trailer shape has a large impact on the the vehicle’s total drag. The greater the The type of vehicle affects aerodynamic aerodynamic drag of the tractor-trailer drag, the more horsepower is required. drag through its size (frontal area) and combination. Some examples of trailers that The total vehicle drag can be broken shape. The following illustration shows have lower aerodynamic drag shapes are: into two main components; aerodynamic two tractor-trailer combinations which, drag and tire drag. Factors affecting as a result of their shorter height these components are: (h2 and h3), have smaller frontal areas Factors than the standard van-type trailer. Influencing Drag Aerodynamic – Vehicle speed Vehicle Frontal area Vehicle Shape Tire – Vehicle Gross Weight h1 Tire Rolling Resistance Both aerodynamic drag and tire drag are influenced by vehicle speed. It is important, though, to note that speed has a much greater affect on aerodynamic drag than on tire drag, Figure 1. Gains in fuel economy can be made h2 by either optimizing or reducing some of the factors affecting drag.

h3

Where: h1>h2

64 Factors Affecting Truck S ECTION N INE Fuel Economy

Drop frame trailers – Less “Open Air” space under the trailer. This also creates less airflow disturbance in crosswind conditions and thereby reduces the amount of drag.

Airflow Rounded Vertical Edge – Maintains “Attached” airflow along the trailer sides, which reduces drag.

Airflow Sharp Vertical Edge

Airflow

Airflow

65 Factors Affecting Truck Fuel Economy S ECTION N INE

C. Use of Aerodynamic Side Gap Seal D. Engine and Driveline Drag Reduction Devices Airflow Characteristics With van-type trailers, certain add-on The use of wide torque band low devices are capable of reducing a vehicle’s RPM engines and wide-step top gear aerodynamic drag. These devices help transmissions, combined with proper maintain an “attached” airflow along the rear axle ratios, leads to fuel economy trailer sides. Again, an increase in drag improvement when operated in the occurs when the airflow becomes “detached.” speed and RPM ranges recommended The favorable impact of roof fairings by engine and vehicle manufacturers. is maximized when the vehicle is operating Vertical Gap Seal Note that a change in the overall in a “head-on” wind condition as shown diameter of the drive axle tires can above. The effectiveness of a roof fairing Vertical gap seal devices reduce drag effectively alter the rear axle ratio and is reduced when the vehicle encounters a by preventing the airflow from entering could adversely affect fuel economy. The “crosswind” (yaw wind) condition. Also, the “open air” space between the tractor determination whether a drive tire change if the trailer height is lower than the top and trailer. Unlike the roof fairing, the produces an increase or decrease in fuel of the fairing, as in the case of a flat-bed impact of this device is maximized economy depends on how much and in trailer, the fairing increases drag because when the vehicle is operating in a which direction engine RPMs are changed. it increases the vehicle’s frontal area. Use yaw wind condition. of a “roof shield” is less effective than a “roof fairing” because it doesn’t channel the wind at the sides. Therefore, a “roof fairing” is preferred.

Gap Also of importance is the amount of gap between the back of the tractor cab and the front of the trailer. The larger the gap, the greater the disruption to the airflow and the resulting drag. This becomes even more important when encountering crosswind conditions (yaw wind). A rule of thumb is for every 10'' over a 30'' gap there is about a 1/10 drop in MPG. Gap Long Wheelbase Tractor

Airflow Yaw Wind Condition

66 Factors Affecting Truck S ECTION N INE Fuel Economy

VEHICLE OPERATION The effect of tire overall diameter on A. General resistance to the total BHP required. In fuel consumption can be illustrated using Consider a typical tractor and van this case, reducing tire rolling resistance an engine fuel map, Figure 2. This is an combination operating at 80,000 lb. by switching to radials has a greater example of a typical part load brake specific gross combination weight and at 55 MPH impact on reducing the total BHP fuel consumption (BSFC) engine map. It on a level highway. No aerodynamic required. shows lines of constant BSFC as a function drag reduction devices are used on of engine BHP output (vertical axis) and either the tractor or the trailer. Using FIGURE 3 engine RPM (horizontal axis). Tractor-Trailer Horsepower Requirements bias ply tires in all wheel positions, the By Component A smaller diameter drive axle tire approximate distribution of horsepower results in an increase in engine cruise requirements is as follows: Van Trailer RPMs, from point A to B. At point B the 400 HP 357 engine is consuming more fuel for the Item Requirement Percent 334 same BHP output. Proper drive train component matching Aerodynamic Drag 104 40 300 257 can provide the most fuel efficient RPM/ Tire Roll Resistance 97 38 237 ground speed combination to maximize Driveline Losses 36 14 200 fuel economy. Engine RPMs can be 179 172 determined using the following formula: Engine Accessories 20 8 257 100 32% Engine RPM=V x TR x AR x (Tire RPM) 38% 28% 60 100 34% Where: In this example, the horsepower 17% 15%

V=Vehicle Speed (mph) required to overcome bias ply tire rolling

Engine Brake Horsepower Required TR = Transmission Ratio @ resistance is essentially the same as that 0 Top Gear (e.g. 1.0 for Bias Rad Bias Rad Bias Rad required to counteract aerodynamic drag. GCW=78,500 GCW=25,000 GCW=78,500 Direct Drive) The total horsepower requirement can AR = Rear Axle Ratio (e.g. 3.70) 55 MPH 65 MPH Tire RPM = Tire Revs Per Mile be lowered with the use of radial ply tires. (obtained from Goodyear’s Because radial ply tires have lower Engineering Data Book or rolling resistance than bias ply tires, Tanker Trailer www.goodyear.com/truck) tire horsepower requirements are lower. 400 As a result, fuel economy is improved. And as the proportion of tire horsepower FIGURE 2 requirement on a vehicle increases, the 300 282 A = Cruise Point @ 0% Grade, gain in fuel economy due to using radial 260 80,000 Lbs. GCW truck tires increases. Some examples 211 360 Lines Of Constant BSFC of tire horsepower requirements as a 200 192 330 percentage of total vehicle horsepower 134 128 300 requirements are given in Figure 3. 41% Increasing Fuel Consumption 100 37% 270 At lower Gross Combination Weights 46% 42% 240 (at the same speed), the horsepower 23% 20%

210 required to overcome the tire rolling A B Engine Brake Horsepower Required resistance is a smaller portion of the 0 180 Bias Rad Bias Rad Bias Rad GCW=78,500 GCW=25,000 GCW=78,500

total brake horsepower required (BHP). 150 This is also true as speed is increased (at 55 MPH 65 MPH

Engine Output - BPH 120 the same GCW). As the vehicle’s aero- Key: HP Required to Overcome – 90 dynamics are improved, as in the case of Aerodynamic Drag 60 a tractor pulling a tanker trailer rather Tire Rolling Resistance 30 than a van trailer, the BHP required to overcome aerodynamic drag is reduced. Driveline Losses

600 900 1200 1500 1800 1200 This has the effect of increasing the Accessory Losses Engine Speed - RPM percent contribution of tire rolling

Source: Mack Truck Engineering, Allentown, PA, Oct. 1992 Source: Goodyear Maintenance Calculations

67 Factors Affecting Truck Fuel Economy S ECTION N INE

B. Type of Haul C. Vehicle Speed FIGURE 5 The ideal type of haul for maximum As vehicle speed is increased, Calculated Horsepower Requirements fuel economy consists of long distance horsepower requirements to overcome the Tractor, 13.5 Ft. High Van Trailer runs at steady moderate speed with a aerodynamic drag increase rapidly. There 400 vs. Total Vehicle Vehicle Speed Requirements minimum of stop-and-go driving and is also an increase in the horsepower 11R22.5 Radial Tires with a minimum of turning. Shorter runs required to overcome increasing tire 300 GCW=78,500 Lb. involve more braking, acceleration and rolling resistance, though this occurs at 200 turning. The engine and tires operate a lower rate. The sum total horsepower Aero. Drag at less than optimum conditions. Fuel requirement for a tractor-trailer vehicle 100 Tire Roll. Resist. economy tends to be reduced. In some increases along a curve which has a Horsepower Required Driveline Losses cases of stop-and-go driving, tires may continually steeper slope as speed is 0 Accessories be operating “cold” part of the time increased. For example, Figure 5 shows 20 30 40 50 60 70 without sufficient continuous driving that the total horsepower requirement at Truck Speed–MPH time for adequate warm-up. A curve of 65 MPH is 40 percent greater than at tire rolling resistance vs. warm-up time 55 MPH for the typical tractor and van- Source: Goodyear Maintenance Calculations as obtained from a laboratory test is type trailer. As a result, fuel economy will A rule of thumb. Increase of given in Figure 4. fundamentally decrease as operating 10 mph = decrease of 1 mpg. speed is increased from 55 to 65 MPH. FIGURE 4 50 Laboratory Tests Truck Tires FIGURE 6 40 Vehicle Speed 75 PSI Rolling Resistance Cold vs. 30 vs. 54 Warm-Up Time Percent Change in MPG & BHP 52 With Capped Air 20 Miles-Pe 11-22.5 Bias Ply r-Gallon 50 LR-F, 4760 Lb. Load 10 48 95 PSI Hot 0 46 44 95 PSI -10 Cold d -20 ire 42 equ r R 11R22.5 Radial we 40 -30 po LR-G, 5300 Lb. Load % Difference in MPG rse 38 Ho 110 PSI Hot -40 cle 36 ehi -50 V

Uncorrected Rolling Resistance–Lb. 015 30 45 60 75 90 105 Elapsed Time–Minutes 30 40 50 55 60 70 Vehicle Speed (MPH)

A 1975 study by the U.S. Department Source: Goodyear Fuel Economy Model Prediction of Transportation and the U.S. Super Hi-Miler and Custom Cross Rib a A calculated curve of the percent difference bias ply tires on the same vehicles to Environmental Protection Agency a concluded that the type of haul (local, in MPG versus speed is shown in Figure 6. determine relative miles per gallon. short-haul, or long-haul trips) has a strong A reduction in MPG of about eight Figure 7 shows the results of the tests effect on fuel economy improvement percent was found for every 5 MPH along with calculated curves passing attributable to radial tires. increase in vehicle speed over 55 MPH. through the test points. The effect of The increased stop-and-go driving For 65 MPH, this would equal close to vehicle gross combination weight on miles of the shorter haul reduces the fuel a mile-per-gallon loss in fuel economy. per gallon is shown. Note that as truck economy gain due to radials. The gross weight was increased, miles per results of the study are given below: D. Vehicle Gross gallon decreased with both the Unisteel Combination Weight radial tire and the bias ply tire; however, Fuel Economy Improvement Due To As gross combination weight is the Unisteel tire gave proportionately Radial Tires Versus Driving Mode increased, tire rolling resistance increases, greater improvement in fuel economy Fuel Economy Driving Mode Improvement and vehicle miles per gallon decreases, as truck gross weight was increased. Local 3 to 5% assuming speed is maintained constant. Tests were run at the San Angelo Short-Haul 4 to 8% To verify this point, fuel economy Proving Groundsa to determine the effect Long-Haul 5 to 9% tests were conducted at the Goodyear of Gross Combination Weight on vehicle aInteragency Study of Post-1980 Goals for Commercial San Angelo Proving Grounds on miles per gallon, comparing 11R22.5 Motor Vehicles; Revised Executive Summary, November 1976. Goodyear over-the-road tractor-trailers. Unisteel radial to 11-22.5 bias ply tires at U.S. Department of Transportation and U.S. Environmental Protection Agency. Unisteel radial tires were compared to 60 MPH. Figure 8 shows that at a GCW of 68 Factors Affecting Truck S ECTION N INE Fuel Economy

you know if you are making any FIGURE 7 10.00R20/10.00-20 Size Tires 13.5 Ft. High Van improvements. Miles Per Gallon vs. Truck Gross Weight Cummins NTC 350 Engine •Try progressive shifting, don’t run V=55 MPH ˚ Test Points against the governor on every shift 7.0 and stay 200-300 RPM below the 12th Gear, G.R.=1.00 governor at cruise (See Figure 9). Texas Shuttle • Stay in as high a gear as possible. 6.0 You can’t lug today’s engines if you can San Angelo Tests maintain speed in any gear. Keep RPM low: below the governor but above 5.0 Radial the minimum RPM recommended Tires by the engine manufacturer. 4.0 • Eliminate unnecessary idling. Shorten Miles Per Gallon Weight warm-up and cool-down times to Empty the minimum recommended by the 3.0 engine manufacturer. Don’t leave the Bias engine idling while you eat lunch Tires or have coffee. 2.0 • Drive defensively. 20 40 60 80 100 120 140 • Cut down top speed. Each MPH over Gross Combination Weight (Thousands of Pounds) 55 costs you 2.2% in fuel costs! •Watch the fueling operation. If you top the tank that valuable liquid could Source: Goodyear Testing Data spill or overflow later when you’re 78,700 lb., the measured MPG advantage E. Driver parked in the sun. of the radial tire was 6.7 percent, while at Driver operating procedures are • Carry as big a load as you can. a GCW of 46,000 lb., the corresponding important factors in achieving maximum Run as few empty miles as you can. value dropped to 1.6 percent. This vehicle fuel economy. The potential •Anticipate traffic conditions. measured reduction in the miles per gallon benefits of lower vehicle aerodynamic Accelerate and decelerate smoothly. advantage of radial tires at the lighter drag, lower tire rolling resistance, and load was more severe than theory would more efficient engines can be offset or Tire care can also affect fuel economy. indicate. Calculations show that the 6.7 even negated by a driver running at a The most important thing a driver can percent advantage should drop to about higher speed. do is to check inflation pressure often 3.5 percent at the lighter load. General rules for the driver to with a calibrated tire gauge and make aThe Effects of Goodyear Unisteel Radial Ply Tires on Fuel follow are:b Economy. Goodyear Tire & Rubber Company Booklet dated 2/77. sure that tire pressure is maintained at a • Keep accurate records of fuel used, recommended high value. (See Figure 14 FIGURE 8 routes taken and loads carried so for effects of inflation pressure on Effect of Gross Combination Weight (GCW) on MPG Advantage of Radial Tires fuel economy.) Percent Increase in MPG Radial/Bias GCW Test Data Calculated FIGURE 9 Progressive Shifting 78,700 6.7 6.7* 46,000 1.6 3.5 Governed *Assumed Same Value As Test Data RPM

Source: Goodyear CFG Tests and Mathematical Calculations

The test data above confirms that the RPM fuel economy advantage of radial truck Engine tires over bial ply tires increases with Idle heavier vehicle Gross Combination RPM Weights. 0102030405060 Miles Per Hour aTire Parameter Effects of Truck Fuel Economy. R.E. Knight, The Goodyear Tire & Rubber Company. SAE Technical Paper 791043, November 1979. Source: Tricks to Save Fuel and Save $$$, DOT Pamphlet HS 804547, June, 1978 b“17 Tricks to Save Fuel and Save $$$$”; Pamphlet DOTHS 804 547, June 1979. 69 Factors Affecting Truck Fuel Economy S ECTION N INE

TIRE SELECTION AND MAINTENANCE A. Tire Rolling Resistance The primary cause of tire rolling FIGURE 11 resistance is the hysteresis of the tire Radial Ply vs. Bias Ply Construction materials/structure, its internal friction, which occurs as the tire flexes when the vehicle moves. Tire rolling resistance acts in a direction opposite the direction of travel and is a function of both the applied load and the tire’s inflation pressure (See Figure 10).

FIGURE 10

Load

Tire Rolling Resistance Direction (Tire Drag) of Travel Unisteel Radial Ply Bias Ply

To accurately determine a tire’s rolling B. Types of Tires Tubeless vs. Tube Type resistance, a controlled laboratory test is Radial Ply vs. Bias Ply Laboratory rolling resistance tests conducted. One method employed, is to The significant differences between indicate that by changing from a 10.00R20 run the tire against an electrically driven these two tires are the angle of body plies tube type tire to an equivalent 11R22.5 67'' diameter flywheel. A torque cell is and the presence of belts. Figure 11 shows tubeless tire in all wheel positions, a used to measure the amount of torque the basic structural differences. Note gain of about 2% in miles per gallon can required to maintain a set test speed at a that the Unisteel radial tire incorporates be achieved at 80,000 Ib. GCW. prescribed test load condition. With this a single radial ply and a multiple belt Larger Diameter Tires torque value, additional adjustments are system. The bias ply tire has six to eight performed to arrive at the tire’s rolling Laboratory tests indicate that, under diagonally oriented plies and no belt the same load and inflation condition, resistance. The laboratory test provides system (although the bias ply tire usually a procedure where environmental larger diameter tires produce slightly has two fabric “breakers” under the lower rolling resistance, as in the case of influences (such as ambient temperature, tread with same angle as the plies). One wind, and road surface texture) can be an 11R22.5 versus an 11R24.5. This can significant advantage of the Unisteel produce an improvement in fuel economy either controlled or eliminated. Also, tire is the relatively low internal friction strict limits are placed on allowable coupled with the reduction in engine RPMs compared to that in a tire using bias due to the larger overall tire diameter on variations in test speed, slip angle, applied ply construction. load, and specified test inflation. These drive axles. (See Section 1-D for the The lower internal friction of the effect of engine RPMs on MPG.) controls insure test repeatability and Unisteel tire helps minimize operating allow the accurate assessment of a tire’s temperatures and rolling resistance, true rolling resistance. major causes of tire wear and excess Tire rolling resistance is commonly fuel consumption. defined in two ways: Unisteel radial ply tires can provide a. Pounds resistance per 1000 pounds fuel savings of six percent and more of load compared to bias ply tires in over-the-road b. Pounds resistance per pound load tractor-trailer applications. (rolling resistance coefficient)

70 Factors Affecting Truck S ECTION N INE Fuel Economy

Wide Base Super Single Tires radial tires instead of 11R22.5 steel the percentage due to steer, drive, and Goodyear Proving Grounds tests show radial tires in the dual positions. A trailer tires. For maximum fuel economy that a fully-loaded tractor-van trailer comparison of the super single versus as well as for best handling, radial tires using Goodyear Super Single Unisteel duals configuration is shown in Figure 12. should be used in all positions of a tractor- 15R22.5 tires instead of dual steel radial trailer unit. Using radial tires especially Retreaded Radial Tires 11R22.5 tires on tractor drives and on designed for trailer application will also Goodyear laboratory tests show that trailer, obtains an average increase of provide an additional improvement in the rolling resistance of newly retreaded seven to eight percent in MPG. fuel economy. For example, the radial radial tires is, on the average, the same Commercial fleet testing using loaded low profile G114 offers approximately a as radial tires with the full original tread. tractor-tanker trailers showed a nine 10 percent lower rolling resistance than There are some differences due to type percent gain in measured MPG through the G159 low profile. of retread, but all newly retreaded radial the use of wide base single 15R22.5 steel For a vehicle already equipped with tires tested exhibited considerably lower radial tires and being switched to another rolling resistance than new bias ply tires. FIGURE 12 type of radial, the percent contribution Radial Wide Base Single Tire Radial Tires on Trailer Axles by axle to fuel economy will differ vs. Radial Dual Tire Assembly The type of tire used on an axle has from that shown in Figure 13. A rule of Wide Base Single a direct impact on the vehicle’s fuel thumb for this case is that the front tires economy. Testing has shown that using contribute about 14 percent of the total, radial tires on trailer axles produces over the drive tires about 39 percent, and the half of the total improvement obtained trailer tires about 47 percent. It should be when converting a vehicle from all bias noted that the actual percent contribution to all radial. Figure 13 details the total may differ from the above due to the percent gain in MPG by switching from effects of vehicle loading, tire inflation, bias to radial tires and, of this total gain, and tire type. Dual Assembly

-Control- FIGURE 13 Radial- All Bias % Difference in MPG Fronts Bias Tires vs. Radial Tires Bias Bias % Gain % of in MPG “All Radial” vs. Control Gain in MPG Bias Bias Radial Fronts 1.0% 17% Radial Drives 1.5% 25% Bias Radial Radial Trailers 3.4% 58%

All Radial- Radial- Radial Trailers Drives

Radial Radial Bias

Radial Bias Radial

Radial Bias Bias

% Gain in MPG vs. Control = 5.9%

Source: Goodyear CPG Test

71 Factors Affecting Truck Fuel Economy S ECTION N INE

FIGURE 14 5.0 Radial Truck Tire Inflation 4.5 4.0 vs. 3.5 Percent Change in MPG 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 Tire Inflation Varied: -1.0 -1.5 Front Axle -2.0 % Difference in MPG -2.5 Drive Axles -3.0 -3.5 -4.0 Trailer Axles -4.5 -5.0 Front, Drive and -5.5 Trailer Axles -6.0

60 65 70 75 80 85 90 95 100 105 110 115 120 Tire Inflation (psi) GCW =78,780 lbs. V = 55 MPH

Source: Goodyear Fuel Economy Model Predictions

C. Tire Maintenance A dual tire load of 4250 Ibs./tire and inflation pressures results in the smallest Inflation Pressure a steer tire load of 5390 Ibs./tire were percent change in MPG. Laboratory tests were conducted to selected along with a specified inflation It must be noted that the tractor- determine the effect of inflation pressure pressure of 100 PSI for all tires. Figure 14 trailer load affects the percent reduction on the rolling resistance of the 295/75R22.5 shows the percent loss in fuel economy in MPG due to underinflation. The G159, G167, and G114 radial truck tires. due to the lower inflation pressures. lighter the GCW, the smaller the percent This laboratory data was used to calculate Operating a loaded tractor-trailer loss in MPG (for the same reduction in the corresponding effect of inflation with inflation pressures of all tires as low tire inflation). pressure on the fuel consumption of a as 70 PSI results in a calculated reduction typical tractor-trailer at 55 MPH on a in MPG of about five percent. The largest A good rule of thumb is that every level highway. The effect of inflation contributor to this loss in MPG is the 10 PSI reduction in overall tire pressure on fuel consumption by axle reduction in inflation pressure of the inflation results in about a one position was also studied. The results trailer tires — it alone accounts for half percent reduction in MPG. are shown on Figure 14. the loss. Varying only the steer tire

72 Factors Affecting Truck S ECTION N INE Fuel Economy

to 1-inch in test #4 does produce a loss in MPG which is significant. FIGURE 15 The greatest loss in MPG was Tractor-Trailer Alignment Effects On Fuel Economy produced in test #5 where a “dog-tracking” Test #1 Test#2 Test#3 Test #4 Test #5 condition was simulated. The trailer tandem axles were misaligned by 1.5- inch though the axles were parallel to one another. The loss in fuel economy was about two percent in addition to increased tread loss. Treadwear As the tread is worn down, tire rolling resistance decreases and vehicle fuel economy increases for both radial and bias ply tires. Proving Grounds tests showed about a one percent increase in miles per gallon for radial tires with tread approximately 30 percent worn.a Laboratory tests show about a 10 percent decrease in rolling resistance for both radial and bias ply tires with tread half worn, and a 20 percent decrease for a fully worn tire. (See Figure 16.)

aTire Parameter Effects on Truck Fuel Economy by R. E. Knight, The Goodyear Tire and Rubber Co. SAE Technical ALIGNMENT Paper No. 791043, November 1979. Steer Tire. Toe-In: 0'' 1/4'' 1/4'' 3/8'' 3/8'' Drive Axle. FIGURE 16 Non-Parallel: 0'' 0'' 1/2'' 1'' 1'' Effect of Treadwear on Truck Trailer Axle. Tire Rolling Resistance Non-Parallel: 0'' 1/2'' 1/2'' 1'' 0'' Laboratory Data *Non-Perpendicular to Frame, 1-1/2'' % Improvement in Fuel Economy: -0.6 -0.8 -1.7 -2.2 100 Bias Ply

Alignment Goodyear fuel economy test program run 80 Radial ply For optimum fuel economy on a tractor- at TRC of Ohio in 1986. These evaluations 60 trailer, and also for optimum tire wear, were Type II tests conducted to SAE J1376 tandem drive axles and tandem trailer standards. Tests #2 and #3 with steer axle 40 axles should be maintained in proper toe-in of 1/4- inch, along with misaligned alignment. Alignment of the vehicle’s tandem axles of 1/2-inch total (difference 20 tandem axles should be considered as in fore and aft distance between axle Percent Rolling Resistance 0 important as the alignment of the steer center lines, from one side of the vehicle 0 20 40 60 80 100 axle tires. The importance of this is not to the other), did not result in a significant Percent Treadwear only reflected in the loss of MPG due loss in MPG versus the specification 10.00R20/11R22.5 Sizes At Approx. Rated to the increase in tire rolling resistance, aligned tractor-trailer. The percent Dual Load And Inflation, LR-F but also in the increase in tire wear as increase in tire rolling resistance due to ‘‘Tips For Truckers’’ FEA/DOT/EPA a result of the greater amount of side- the slip angles (under .2°) generated by Document GPO 910-940 scuffing. The effects of drive axle and these misalignment conditions is small. Calspan Rep. DOT-TST-78-1 trailer axle alignment is even greater What is of greater significance is the Goodyear Test Calculation, Based On Goodyear Fuel due to the number of tires involved: loss in tire treadwear life. Economy Test eight vs. two. Increasing the steer tire toe-in to 3/8- Figure 15 illustrates the results of a inch and the tandem axle misalignment Source: Goodyear Fuel Tests at TRC of Ohio, 1986 73 Factors Affecting Truck Fuel Economy S ECTION N INE

ENVIRONMENTAL CONDITIONS A. General C. Road Surface Another study on passenger tiresc Conditions external to the vehicle The type of road surface can affect investigated the effect of road roughness can have a strong influence on the fuel tire rolling resistance. Smooth-textured (not surface texture) on rolling losses economy achieved by a given driver and highway surfaces provide the lowest and concluded: tractor-trailer/tire combination. Some of rolling resistance, while coarse-textured 1. Road roughness increases both the greater influences are exerted by: surfaces give the highest tire rolling resist- rolling and aerodynamic losses (the Winds ance and the lowest fuel economy. latter due to vehicle pitching action). In a test,b it was found that a coarse 2. Road roughness significantly increases Road Surface chip-and-seal pavement surface gave an vehicle rolling losses due to energy Ambient Temperature increase in passenger tire rolling resistance dissipation in the tires and suspension. Terrain of 33 percent over that obtained on a 3. Tests on rough roads led to increases typical new concrete highway surface. in rolling losses as large as 20 percent, B. Winds Relative rankings of the test surfaces were: in addition to introducing increases in aerodynamic drag. Headwinds and crosswinds reduce Relative truck fuel economy by increasing truck Rolling Truck fuel economy may be expected airspeed and/or yaw angle, thus increasing Surface Resistance % to be influenced in a manner similar to aerodynamic drag. To avoid excessive Polished Concrete 88 that of passenger cars; by the surface fuel consumption in sustained strong New Concrete 100 condition of the roadways traveled and headwinds, a decrease in truck highway Rolled Asphalt by the type of materials used in the speed is indicated. (rounded aggregate) 101 pavement—especially in asphalt/ crushed Crosswinds also tend to diminish the Rolled Asphalt (medium stone mixes. Tire treadwear as well as effectiveness of aerodynamic drag-reducing coarse aggregate) 104 vehicle fuel economy may be influenced devices such as cabmounted flow deflectors. Rolled Asphalt by the particular area of the country Tailwinds are generally beneficial in (coarse aggregate) 108 being traversed, depending upon the increasing fuel economy because of the Sealed Coated Asphalt sharpness and hardness of the local reduced airspeed for a given highway (very coarse) 133 crushed stone used in asphaltic concrete speed. However, if the driver takes road pavement mixes. advantage of the tailwind and increases his highway speed, the fuel economy bL. W. DeRAAD “THE INFLUENCE OF ROAD SURFACE TEXTURE ON TIRE ROLLING RESISTANCE”, SAE gains will be reduced or lost completely. TECHNICAL PAPER 780257 PRESENTED AT THE CONGRESS AND EXPOSITION, COBO HALL, DETROIT, FEBRUARY 27 - MARCH 3, 1978.

cSteven A. Velinsky and Robert A. White, “Increased Vehicle Energy Dissipation Due to Changes in Road Roughness with Emphasis on Rolling Losses.” SAE Technical Paper 790653 Presented at Passenger Car Meeting, Dearborn, Michigan, June 11-15, 1979.

74 Factors Affecting Truck S ECTION N INE Fuel Economy

5.4 MPG vs. Average Daily Ambient Air Temperature

5.2 * 5 * * 4.8 ** *

MPG * * *** * * *** 4.6 * * * * * * * *** * * * * ** * 4.4 * ** * * * * * * * 4.2 * ** 02040 60 80 100

Average Daily Ambient Air Temperature

D. Ambient Temperature E. Terrain 2. Altitude High ambient temperatures reduce 1. Grades As altitude increases, air density and tire rolling resistance. High temperatures Most proving grounds fuel economy atmospheric pressure decrease. At 5,000 also reduce atmospheric density, resulting testing is done on level terrain, and most ft. altitude, for example, air density in a in lower aerodynamic drag. However, fuel simplified calculations relating various standard atmosphere is 14 percent less economy performance of non-turbocharged truck and tire parameters to truck fuel than at sea level. This percent reduction diesel engines may be adversely affected economy also assume level terrain. in air density also applies to reduction in by high ambient temperatures, and this The effect of traveling up a grade aerodynamic drag, all else being equal. would tend to negate some of the gains is very significant in terms of reducing Tire rolling resistance is not affected resulting from lower tire drag and lower truck fuel economy. Assuming a one by altitude, per se, unless cold inflation aerodynamic drag. percent grade and an 80,000 pound pressure is set at lower altitudes and not Cold weather operation has an tractor-trailer, there will be a rearward changed as altitude of operation increases opposite effect: tire drag and aerodynamic force exerted by gravity of 80,000 during the course of the trip. For example, drag increase at the lower ambient pounds x .01 = 800 pounds. a tire with a gauge cold inflation pressure temperatures. The greater thermal Proving grounds tests over a measured of 100 PSI at sea level, if taken to 5,000 ft. efficiency of internal combustion engines mile on a road with a 0.1 percent grade altitude at the same ambient temperature, at low ambient temperature is usually consistently showed eight to ten percent would have a gauge cold inflation pressure cancelled by longer warm-up times and lower miles per gallon, comparing going of about 103 PSI. This added inflation longer idling times to maintain cab uphill to the west with going downhill would tend to reduce tire rolling resistance. temperatures during stopover periods. to the east. This difference was obtained Altitude effect on engine fuel economy Thus, wintertime fuel economy is generally using a typical tractor-trailer at 55 MPH performance depends on the particular lower than that obtained in the summer. and at a gross combination weight of engine design and whether or not it is 78,500 pounds. supercharged or tuned for high-altitude Traveling on a downhill grade improves operation. fuel economy and in hilly country helps to counteract the losses in fuel economy sustained by traveling upgrade.

75 Factors Affecting Truck Fuel Economy S ECTION N INE

TIRE DESCRIPTION AND SPECIFICATIONS • Static Loaded Radius (SLR)—The Goodyear Unisteel distance from the road surface to Low Profile Radial the horizontal centerline of the wheel, under dual load 1 • Minimum Dual Spacing—The minimum dimension recommended from rim centerline to rim centerline for optimum performance of a dual wheel 4 9 installation • Loaded Section (LS)—The width of 2 the loaded cross-section Tire profile or cross-sectional shape is described by aspect ratio (AR): the ratio 8 of section height (SH) to section width (SW) for a specified rim width. For a 5 7 given tire size, the aspect ratio for a Goodyear radial truck tire is the same 6 10 3 as for a bias ply truck tire.

Cross-Sectional View of Typical Tire Section 1. Tread—This rubber provides the 7. Chafer—A layer of hard rubber that Width (SW) interface between the tire structure resists rim chafing. Outside Section and the road. Primary purpose is to Diameter 8. Radial Ply—The radial ply, together Height (SH) provide traction and wear. (OD) with the belt plies, withstands the 2. Belts—Steel cord belt plies provide burst loads of the tire under operating Rim strength to the tire, stabilize the pressure. The ply must transmit all Flange Width Height tread, and protect the air chamber load, braking, and steering forces from punctures. between the wheel and the tire tread. Minimum 3. Stabilizer Ply—A ply laid over 9. GG Ring—Used as reference for Static Loaded Dual the radial ply turnup outside of the proper seating of bead area on rim. Radius (SLR) Spacing bead and under the rubber chafer 10. Bead Core—Made of a continuous that reinforces and stabilizes the high-tensile wire wound to form a bead-to-sidewall transition zone. high-strength unit. The bead core is Loaded Section 4. Sidewall—The sidewall rubber must the major structural element in the (LS) withstand flexure and weathering plane of tire rotation and maintains while providing protection for the required tire diameter on the rim. Safety Warning the ply. Terms Used To Describe Tire/ Serious Injury May Result From: 5. Liner—Layers of rubber in tubeless Rim Combination •Tire failure due to underinflation/ tires especially compounded for • Outside Diameter (OD)—The overloading/misapplication—follow resistance to air diffusion. The liner unloaded diameter of the tire/ tire placard instructions in vehicle. in the tubeless tire replaces the rim combination Check inflation pressure frequently innertube of the tube-type tire. • Section Width (SW)—The maximum with accurate gauge. width of the tire section, excluding • Explosion of tire/rim assembly due to 6. Apexes—Rubber pieces with any lettering or decoration improper mounting—only specially selected characteristics are used to • Section Height (SH)—The distance trained persons should mount tires. fill in the bead and lower sidewall from the rim to the maximum height When mounting tire, use safety cage area and provide a smooth transition of the tire at the centerline and clip-on extension air hose to inflate. from the stiff bead area to the flexible sidewall.

76 Factors Affecting Truck S ECTION N INE Fuel Economy

SUMMARY The average fuel costs of a given trucking fleet are related to two factors: •Average fleet miles per gallon •Average fuel cost per gallon While it seems little can be done at the present time to reduce fuel cost per gallon, there are steps that can be taken to increase average fleet miles per gallon. The miles per gallon achieved by a given truck depends on many factors, the major ones being: •Vehicle, Engine and Accessory Design and Maintenance •Vehicle Operation •Tire Selection and Maintenance • Environmental Conditions Major fuel-saving steps to apply to trucking operations are: 1. Use fuel-efficient high torque rise, lower RPM engines. 2. Use engine accessories with reduced horsepower requirements, such as clutch fans, synthetic lubricants, etc. 3. Use aerodynamic drag reduction devices such as flow deflectors and rounded trailer fronts and corners on tractors pulling van-type trailers. Cover open-topped trailers with a tightly-stretched tarpaulin. 4. Use radial tires in all wheel positions, trailer as well as tractor. 5. For best fuel economy, do not allow radial tires to operate below 95 PSI cold inflation pressure. 6. Do not exceed the tire’s rated speed; operate truck fully loaded as much of the time as possible to increase ton-miles per gallon.

77 Factors Affecting Truck Fuel Economy S ECTION N INE

APPENDIX Fuel Economy Test Procedures There are three fuel economy test A. SAE Type I B. SAE Type II procedures which have been developed The SAE Type I procedure is best used The SAE Type II procedure is best by the Society of Automotive Engineers to evaluate a component which can be used to evaluate a component which (SAE) and which are currently being easily switched from one vehicle to another. requires a substantial amount of time used by vehicle manufacturers, tire The procedure requires two vehicles for removal and replacement. manufacturers, and by some fleet owners. of the same specification; these are run This procedure also requires two These offer a standardized method to simultaneously and are identified as vehicles, though they do not have to be evaluate either a complete vehicle or a vehicles “A” and “B.” of the same specification. The vehicles component. Consideration has been given The minimum mileage required for are identified as “C” and “T.” Vehicle “C” to the effects of environmental conditions one complete test cycle is 200 miles. is the control vehicle and as such is not (such as those described in Section 4), This is composed of a 100 mile round modified during the course of the test; and their effect on fuel economy results. trip with the test component on vehicle vehicle “T” is the test vehicle which is This is accomplished by requiring the “B” and then another 100 mile round trip used to evaluate the test component. use of a control vehicle which is run with the test component on vehicle “A.” The minimum mileage for a complete simultaneously with the test vehicle. Since a round trip must start and finish test is 240 miles. This is composed of Environmental conditions should affect at the same location, the minimum three valid test runs of 40 miles (minimum) both vehicles in a similar manner so that length of the outbound and inbound each with vehicle “T” running a baseline for a set of tests, the ratio of either the test leg is 50 miles. component (control component) and fuel used or the MPG of the test and On the outbound test leg vehicle “A” then three valid test runs of 40 miles control vehicles should be relatively leads vehicle “B” (approximately 200 - (minimum) each with vehicle “T” running constant even though the actual values 250 yard separation). At a point halfway the test component. Vehicle “T” starts of either the fuel used or the MPG may through this test leg (approx. 25 miles) off first; after approximately 5 minutes vary from test to test. vehicle “A” slows down to allow vehicle vehicle “C” begins its run. The test run A brief description of each procedure “B” to take the lead. At the completion of starts and finishes at the same location. is listed along with some of their important the outbound leg, fuel tanks are weighed For each test run the amount of fuel requirements. or fuel meter readings are recorded. On used by vehicle “T” is compared to that the inbound test leg, vehicle “B” leads “A” used by vehicle “C” in the form of a T/C (same separation distance as outbound ratio—the quantity of fuel used by vehicle leg). Also at a point halfway through the “T” divided by the quantity of fuel used test leg “B” slows down to allow “A” to by vehicle “C.” To be considered valid take the lead. Upon completion, fuel is test runs, three T/C ratios within a two weighed or meters recorded. The test percent band must be obtained. This may component is then switched between require one or more additional test runs. vehicles and another round trip is made. Test speed — as required The amount of fuel used by vehicles Vehicle loads — not required to “A” and “B” when they are operating be the same with the test component is compared to Vehicle that used by both vehicles without the warm-up — minimum of one test component. hour at test speed Test speed — as required Test run time — elapsed time of the Vehicle loads — within five percent test runs must be of each other within .5% Vehicle warm-up — representative of fleet operation or not less than 45 minutes at test speed

78 Factors Affecting Truck S ECTION N INE Fuel Economy

C. SAE Engineering Type For each test run a T/C ratio is The SAE Engineering Type test provides obtained. This is the MPG of vehicle standardized procedures to evaluate fuel “T” divided by the MPG of vehicle “C.” economy for different modes of operation, A test is considered valid if for the three such as Long Haul Cycle, Short Haul runs (or more) the spread of T/C ratios Cycle, Local Cycle, and Transit Cycle. doesn’t exceed three percent of the This procedure is more controlled than mean value. either the Type I or II tests both in terms Test speed — 55 MPH of test site conditions and test procedures. Vehicle loads — as required The effect of this is reflected in greater Ambient repeatability. This procedure is best run temperature — 60 to 80° on a test track. Wind velocity — average wind speed The procedure requires two vehicles not to exceed preferably of the same specification. 15 MPH The vehicles are identified as “C” and “T.” Vehicle Vehicle “C” is the control vehicle and is warm-up — minimum of 1 hour not modified during the course of the at 55 MPH test. Vehicle “T” is the test vehicle which is used to evaluate the test component. Long Haul Cycle: The minimum mileage for a complete test is 180 miles. This is composed of three valid 30 mile test runs with vehicle “T” running the baseline component (control component) and three valid test runs with “T” running the test component. The start time of the vehicles should be staggered such that they don’t aerodynamically interfere with each other. Halfway through each test run (15 miles) the vehicles are to come to a complete stop, idle for one minute and then accelerate back to the test speed. A test run starts and finishes at the same location. If this procedure is not run on a track it can be handled by running 15 miles outbound and 15 miles inbound.

79 Tire Repairs S ECTION T EN

Tire Repairs

High loads, speeds and tire operating

pressures place critical importance on tire

maintenance practices. Tire repair is an

integral part of maintaining radial tires to

achieve the maximum in performance and

value. Because of this, personnel should be

adequately trained in repair procedures and

techniques, and only the highest quality

repair materials should be used.

80 S ECTION T EN Tire Repairs

Tire repairs normally made by fleet Significant cuts and cracks in the The cutaway view of the Unisteel tire operators and tire service centers are sidewall area should be spot repaired in Figure 10.1 shows the construction limited to simple punctures such as nail as soon as possible to prevent the need typical of Goodyear radial truck tires. holes. Anything more extensive, such as for a major section repair. Frequent tire The single radial ply of steel cord as spot, reinforcement, or section repairs inspection in service is recommended. well as the four steel cord belt plies should be referred to an authorized full This section gives information are evident. service Goodyear retreading and concerning tire damage, extent, and repair facility. location, to help determine whether or not section repairs are feasible.

Figure 10.1 Cutaway View of Unisteel Tire

81 Tire Repairs S ECTION T EN

NAIL HOLE REPAIR PROCEDURES Radial tire nail hole repairs up to 3/8-inch diameter (9.5 mm) may be made in the tread face as long as the nail hole is at least one-inch inside the shoulder. All injuries outside this point should be treated as a section repair. RADIAL ONLY

Radial Only

Repair Area

Figure 10.2 Any number of repairs in the approved Figure 10.4 Beads in relaxed position. Using a car- Figure 10.6 Brush chemical cure cement on nozzle and crown area only tread minus outer 1” area bide cutter, drill the injury from the inside to clean and insert into the hole while turning clockwise. (use outer grooves as a guide). Refer larger injuries to prepare the injury for the plug. a full service repair shop. Do not overlap patches.

Figure 10.3 Dismount tire. Remove puncturing object. Figure 10.5 Apply a coating of chemical cure cement Figure 10.7 Apply air pressure (80 psi) to top of gun. Using a probing awl, determine the size and extent to the leading 1/3 of the cured plug. Remove This presses the plug through the nozzle into and of injury, and angle of penetration. Thoroughly the end of the plug insertion tool and insert the plug through the injury. Remove the gun while turning in a inspect the inside of the tire for additional damage. into the nose piece. Do not contaminate the plug or clockwise direction. Clean area to be repaired inside of tire cross thread the nose piece. If a pull-through plug is used, insert the plug into with scraper and pre-buff cleaner. the wire puller, apply chemical vulcanizing cement to the leading 1/3 of the cured plug and pull through the injury from the inside of the tire. 82 S ECTION T EN Tire Repairs

Figure 10.8 Cut excess plug 1/16'' above the liner Figure 10.10 If using a chemical cure repair patch, surface on the inside. Do not stretch plug. cement the back of the patch and the buffed liner with chemical vulcanizing cement. If using a “Versacure” type repair patch, cement the buffed liner only. Thoroughly cover the cemented areas with a light, even coat. Allow proper drying time before applying the repair patch. RADIAL ONLY

Radial Only

Figure 10.9 If necessary, repeat the liner cleaning Figure 10.11 Place beads in a relaxed position. Center procedure with pre-buff cleaner. Using a low-speed the patch over the plug and stitch the patch from the grinder, buff the liner to an RMA1 texture finish. center out. Directional arrows on the patch Then vacuum to remove dust and debris. must be properly aligned, after stitching is *When using chemical cure MCX series patches, complete. Apply a coat of butyl liner repair sealer to use chemical vulcanizing solution on the buffed the patch edges and the over buffed liner. Trim the excess liner and back of repair patch for heat and plug no more than 1/8” above the outside tread surface. non-heat applications.

83 Tire Repairs S ECTION T EN

RADIAL SECTION REPAIR LIMITS IN SIDEWALL AND SHOULDER AREA Most sidewall injuries will be the NOTE split-type, caused by snags and punctures. Wire must be sound and free of rust. Maximum injury sizes for sidewall and Maximum shoulder and sidewall injury shoulder repairs are shown below. for typical line haul medium truck tire The number of these section repairs is 1'' wide (circumferentially) x 4'' should be limited to 2 per tire for line long (radially). See authorized Goodyear Center Patch haul service and 3 for city service with a full service repair facility for other Over Injury maximum of 2 repairs per any 90 degree appropriate limits. quadrant of the tire as long as repair patches do not overlap and the same ply wires are not affected by more than one injury. Spot repairs may be made without Figure 10.16 limit providing that the body plies are Repair Patch not exposed or damaged. Existing repairs Should Be must be reworked if loose or questionable. Centered Over Injury

Max Repair

Figure 10.14 Y Body Ply X

Maximum Shoulder and Sidewall Repair Size

Figure 10.12

Maximum Injury Size Casing Size (b) (X) Width (Y) Length 10.00R20/22 Cable 1-1/2 11.00R20/22 1/8 3-3/4 11R22.5/24.5 12R22.5 3/8 5 Figure 10.15 285/75R24.5 295/75R22.5 1/2 5 15R22.5 3/4 5 16.5R22.5 18R22.5 14

Figure 10.13

84 S ECTION T EN Tire Repairs

APPLICATION OF CENTER-OVER-INJURY SECTION REPAIRS RADIAL PLY TIRES Non-Repairable Areas Tire Size Dimension A All “LT” Tires 2-1/2'' 8.25R, 9.00R, 10.00R 3'' 9R, 10R, 11R 3'' 16.5, 18R22.5 3'' 285, 295, 305, 315/75R, 80R, 85R 3'' 11.00R, 12.00R 3-1/2'' 12R, 13R/FR20 3-1/2'' 12/80R, 13/80R, 14/80R 3-1/2''

Figure 10.20

Dimension A

Figure 10.17

Sidewall or Shoulder Repair Center Patch Over Injury Figure 10.21

Figure 10.18 CROWN REPAIR LIMITS Injuries up to 1-1/2'' diameter may be repaired in line haul and city service radials depending on tire size. Radial mileage tires used in city Tread Repair bus service only may be repaired up to Center Patch 1'' diameter. See authorized Goodyear Over Injury full service repair facility for other appropriate limits. Figure 10.19

85 Retreading S ECTION E LEVEN

Retreading

The purpose of this Recommended Practice

is to provide guidelines for the evaluation and

selection of a retread supplier for truck tires.

86 S ECTION E LEVEN Retreading

INTRODUCTION PLANT INSPECTION Tire retreading is a manufacturing policy on both retreading and repairs? Plant Image process. Therefore, any retreaded tire is Is there any casing warranty? 1. Overall plant appearance should be only as good as the workmanship and clean and orderly. When the retreader has satisfied that the quality control in the plant that 2. The plant must have adequate layout it can meet the needs in these areas, a manufactured it. To thoroughly evaluate and space for effective handling visit to the plant for an evaluation of a retread supplier, one must look at both of tires. work methods and quality procedures the product and service. For these reasons, 3. The facility should be well lighted is invaluable. a plant visit is important in the selection and adequately ventilated. A plant inspection is divided into of a retreader. 4. The retread plant must have eight areas of concern. They are in an production capacity to handle order that should be convenient for a your service needs. tour of the plant. Many of the questions PLANNING A 5. The retread plant should be raised will not have absolute or totally inspected and certified by an RETREAD PLANT VISIT objective answers. Judgment, and the industry association or supplier. Prior to a plant visit, a few items retreader’s response to questions, will should be considered. These may affect provide the answers needed to rate any Casing Inspection whether the retreader in question individual retread plant. The inspector’s job is to determine qualifies as a prospective supplier. It is suggested to reproduce the whether the used tire is retreadable These considerations include: sections listed under “Plant Inspection” as presented. If not, the inspector will 1. Does the retreader use quality in this Recommended Practice for use usually make recommendations as to the products and procedures from a in discussion with the retreader and its disposition of the used tire: scrap; repair quality tread rubber manufacturer employees, and also reproduce the and then retread; return to the customer providing assistance to the “Retread Plant Inspection Checklist” for adjustment consideration; etc. The retreader, ie: appearing at the end of this Recommended ability to analyze worn and damaged a. Production associate training Practice to use during a retread plant tires is a skill usually acquired through b. Q.A. & technical assistance visit. The checklist provides space to experience and also requires a working c. Plant certification rate each item checked. knowledge of all the various steps of the 2. Does the retreader offer any of the retread process. Look for an experienced following services you may need? person in this position. a. Pick-up and delivery of tires 1. Inspection area must be well lighted. b. Flat repair 2. Tires must be dry before being c. National account program inspected. d. Tire mounting and demounting 3. Check to see whether the retreader e. 24-hour road service is using any electronic, ultrasonic, 3. Is the retreader making repairs: or other “high-tech” inspection a. To both bias and radial casings? equipment. b. To all types and levels of tire 4. Check the retreader’s system of injuries: spot repairs, bead tracking casings in process to repairs, reinforcements, and ensure that all of your casings get section repairs? back to you and that they are 4. What is the retreader’s turn-around returned on schedule. time? Seven day turn-around is typical. 5. Does the retreader define warranty

87 Retreading S ECTION E LEVEN

Casing Repairing Buffing After Buff Preparation The repair person’s job is to make The buffing operation is used to size, Items listed in this category include structural repairs to damaged areas of shape, and texturize the crown of the a number of interim steps between the the casing so the casing will be sound casing in preparation for the application major operations of buffing and tread enough to last through a new tread life. of a new tread. application. Depending upon individual 1. A separate, clean, well lighted area 1. All casings must be buffed to retread plant procedures, these steps should be used for the repair area. a predetermined: might be performed individually, or as 2. Wall charts should be posted showing part of the repairing, buffing, or tread a. Crown width procedures, patch usage, cure times, application steps. b. Crown radius etc. Retreaders’ recommendations c. Specified remaining undertread 1. An after-buff inspection should be and procedures must be followed. d. Symmetrical profile performed to ensure the buffing 3. Repair materials must have current e. Diameter and bead to bead process has not uncovered any manufacture date codes or expiration dimensions in mold cure systems previously unnoticed defects. date codes. Most repair materials 2. All holes, cuts, and penetrations must have a shelf life and, ideally, should 2. Buffers should be computer or be probed to determine the severity be stored in a cool, dry place. template controlled. Buffer operators of the injury and to ensure that all 4. All repair materials, cements, and should not override computer foreign material has been removed. supplies should be from the same programs or templates. manufacturer. It is a questionable 3. Wall charts, or other ready references, 3. Buzz-out/skive-out. Note that this practice to mix brands since not should be in use to determine the is the single most neglected or all products are compatible. correct specification for each tire mishandled detail and one of the 5. The retreader should identify repairs. as referred to above. major causes of retread failures. All dirt, rust, and foreign material must (Retread plant name, date of 4. All exposed cords (fabric or steel) be removed; all separated and/or repair, etc.) must be “finished” to remove all laminated rubber must be removed 6. Check to see that the repair shop fuzz and frayed ends. is using the proper RPM hand – leaving a clean, solid surface for the 5. All exposed cords (fabric or steel) buffing tools. filler material to adhere to. Any buzz- should be coated with cement or a. A high RPM grinder is used for out that exceeds the specified limits other similar treatment promptly grinding steel. must be treated as a section repair. after completion of the buffing b. A low speed grinder is used on 4. Tires must be measured for proper process. Steel cords must be rubber. Use of a higher RPM mold fit or tread length in the case coated within 15 minutes. tool will scorch the rubber, of some pre-cure methods. 6. All untexturized areas such as tread reducing adhesion. (Gummy 5. Cement is used to enhance the grooves and irregular wear spots rubber build-up on buffing rasp adhesion between the new tread must be hand-treated to remove and smoke generated at the and the prepared casing. buffed surface are indications oxidation and surface dirt. a. The tire should be clean of scorching.) 7. Buffing rasps should not be smoking before cementing. excessively. This would be an b. Adequate drying time must be indication of scorching and will allowed prior to tread application. result in poor adhesion. c. Cement container must be 8. Buff texture must be consistent with protected from air supply line Rubber Manufacturers Association moisture and oil contamination. www.rma.com guidelines. See the d. Check manufacturer’s date code RMA buffed texture chart. or expiration date on cement 9. Buffed tires must be handled in such container. Cements have a shelf a way as to ensure the buffed surface life and must be kept fresh. is not contaminated. e. The “in use” cement container must be kept mixed while being used to eliminate the possibility of solid settling out from the mixture.

88 S ECTION E LEVEN Retreading

Tread Application Curing staples. Staples may penetrate the Tread application is the fitting of There are two popular cure systems: tubeless liner, creating air leaks. Holes new tread rubber (which will become 1. Mold Cure. Tread rubber is applied to from staples can allow moisture to the new tread) onto the prepared casing. the tire uncured. The prepared tire enter and create rusting of the steel This rubber must be the correct width is placed in a mold (matrix) which body in steel cord tires. and thickness. It must be centered and it imprints the tread pattern as the Final Inspection & Finish must be circumferentially consistent. rubber is cured directly on the casing. After curing, a final inspection should 1. All buzz-outs should be filled flush 2. Pre-Cure. The previously cured tread be made of the finished retread. At this with the buffed surface. rubber, with the tread design already time, the finished tire may be trimmed 2. All exposed cord (fabric or steel) formed, is applied to the tire with a of rubber flashing or overflow, painted, should be covered with cushion gum thin layer of uncured cushion gum and tagged for delivery. before the tread rubber is applied. on its base to serve as an adhesive. 1. The inspection area must be 3. Check to see what brand, product The assembly is then placed in a well lighted. heated, pressurized chamber where line, and grade of tread rubber is 2. The tire must be inspected on the cushion gum is cured to both being used. It is the retreader’s a spreader. responsibility to notify his customers the tread rubber and the casing, 3. It is recommended that tires be if this specification is changed. forming the bond between the two. inspected immediately after 3. Time, temperature, and pressure are 4. Raw materials (tread rubber, cushion, completion of the cure cycle, the three requirements of any retread etc.) must be fresh. Check the while still hot. Separations and cure system. Increasing or decreasing manufacturer’s date code or expiration other flaws that are visible while any of these factors from an optimum date code on the container, and hot may disappear as the tire cools. ideally, it should be stored in a cool, level will affect such things as tread 4. The inside of the tire must be dry area. adhesion, mileage, and casing life. The optimum time/temperature inspected to ensure that all patches 5. With pre-cure treads there should specification is determined by are properly bonded and that no be no more than two splices per completing a thermocouple test in bubbles, dimples, or buckles are tire. Observe the procedures and that particular curing equipment. evident in the patch or tire liner. materials used for making tread 5. The outside of the tire should be splices for quality. a. Check to see if the retreader has had thermocouple tests inspected for appearance. 6. Short tread pieces (18” or less) made in his equipment. 6. All staples must be removed from should not be used to make splices. b. Ask to see what control systems precure tread splices and wicking 7. With pre-cure tread application, or procedures are used to ensure material. “stitching” must be performed in that all tires are cured at the 7. Check to see that the DOT such a way as to eliminate trapped correct temperature, pressure, identification number has been applied air pockets. and time period. to the tire. Ideally, the DOT number 8. Adhesive surfaces of tread rubber 4. All envelopes, diaphragms, and should be located away from the and cushion, and the buffed surface curing tubes must be leak free. bulge width of the tire so it will not of the tire, must be kept free of 5. Check for steam and air leaks which be scuffed off in service. contamination from hands and may contribute to improper cure. 8. All rejected returned-as-received (RAR) other sources. 6. Tires must be stored in such a manner casings should have the rejection as to avoid distortion of the tread cause marked on the tire with the and/or casing before curing and area of injury clearly identified. immediately after. 9. Finished retreads should be painted 7. Wicking material used with pre-cure and all crayon marks should be systems must not be stapled into painted over to give the final product the tire sidewall or bead. Sidewalls an appealing appearance. and beads are not designed to accept

89 Retreading S ECTION E LEVEN

DEFINITIONS Base Width – A measurement of that Tread Cracks (Channel or Groove) – retreading in some processes. portion of the tread rubber that joins Cracks in the base of the tread Gauge – Thickness, usually expressed to the buffed surface of the worn tire. grooves or voids. in thirty-seconds of an inch, by the Beads – The anchoring part of the tire Buckled – Any gross distortion decimal system, or in millimeters in the that is shaped to fit the tim. Made of of the tire body or tread area metric system. high tensile steel wires wrapped and evidenced by wrinkling on the Injuries – A break or cut of any shape reinforced by the plies. inside of the casing. caused by a penetrating object or severe Bead Sealing Area – The flat area and Buffed Contour – The shape of the buffed scuff or impact. heel area of the bead that contacts the rim. tire that usually includes a specified Injury Size – Widest opening in the With tubeless tires, the bead area seals radius and width. cord body after skiving and buffing. to the rim and rim flange to retain air. Buffed Radius – A measure of the buffed Inner Liner – The tubeless tire inner Belted Bias Tires – Tires constructed so surface curvature from shoulder to shoulder. surface used to retain the inflation media. the ply cords extend from bead to bead Buffed Texture – That surface produced and are laid at alternate angles Kinked (Beads) – A sharp permanent bend by buffing, rasping, or cutting as defined substantially less than 90˚ to the in the bead wires at one or more points by The Rubber Manufacturers Association, centerline of the tread. On top of the around the circumference of the bead. “Buffed Textures” (RMA Shop Bulletin No. 29, body plies are two or more belt plies www.rma.org). Load Range – Specified as a letter (A, B, extending approximately from shoulder C, etc.) to identify a given size tire with to shoulder running circumferentially Casing – The complete tire structure. its load and inflation limits when used in around the tire at alternate angles. Cement – An adhesive compound used a specific type of service as defined in Bias Ply Tires – Tires constructed so the to provide building tack. May be brushed Tire and Rim Association, Inc. (or ply cords extend from bead to bead and or sprayed on the buffed surface. equivalent) yearbooks. are laid at alternate angles substantially Check Template – A precut pattern used Matrix – Aluminum, rubber, or steel less than 90˚ to the centerline of the tread. to determine the contour of a buffed tire rings or segments that form the cavity Body Plies – Layers of rubber-coated to check compatibility to a matrix. in which a tire retread is cured and with parallel cords extending from bead to bead. which the tread design is formed. Cords – The individual strands forming Breaks (Cracks) – A surface opening the plies in a tire. Nail Hole – A penetration caused by a extending into or through the plies. small, sharp object, 3/8 inch maximum Cross Section – The section width of a diameter. Flex Breaks – A break into or tire casing. through one or more plies, usually Outside Steam Bag – A flexible bag, Cure – The process of vulcanization parallel to the beads. usually reinforced, used to encompass of rubber by applying heat and pressure the tread and tire shoulders of a tire Impact Breaks – A star- or X-shaped for a specified time. being retreaded or repaired. or diagonal break into or through Curing Tubes – Special tubes placed plies, usually visible from the inside Plies – Layers of rubber-coated within the tire while curing. of the tire. parallel cords. Diaphragm – A flexible sheet used to Radial Crack – A crack in the outer encompass part or all of a tire during surface of the tire, usually in the sidewall area proceeding perpendicular towards the bead.

90 S ECTION E LEVEN Retreading

Protector Ply – A ply added primarily Precured Tread Retreading – Splices – A junction of the ends of any for casing protection which in some Replacement of the worn tread tire components. cases may be removed during retreading. areas with pre-vulcanized treads Spot (Repair) – The replacement of containing the tread design already Radial Tire – A tire that has ply cords rubber only in an injury that penetrated cured in. from bead to bead extending at about to no more than 25% of the body plies 90˚ to the centerline of the tread. On Sections – Reinforced repairs made to a in a radial tire. Rubber replacement only. top of the body plies are two or more casing where an injury larger than a nail Stitching – A method used to both remove belt plies of rubber-coated cords extending hole extends through more than 75% of trapped air and improve rubber contact approximately from shoulder to shoulder the plies or through the casing in the for better adhesion. and running circumferentially around tread or sidewall areas. the tire at alternate angles at substantially Synthetic Rubber – Man-made rubber. Separation – Lack of adhesion or cohesion less than the ply cord angle. between any adjacent materials in a tire. Texture – (See Buffed Texture) Reinforcement (Repair) – Any material, Tread Separation – Pulling away of Tread – That portion of a tire that comes usually rubber and fabric, vulcanized to the tread from the tire body. in contact with the road. a tire to add strength to the tire cord body at an injury. Repairs to over 25% Retread Separation – A separation Tread Design – The non-skid pattern or of plies usually require reinforcement. between the tread rubber and the design on the tread of a tire. Repairs of more than 75% of plies are buffed tire casing. Tread Grooves – The space between usually called section repairs. Ply Separation – A separation two adjacent tread ribs, lugs, or bars. Repair Material – Any rubber compound between adjacent layers of Undertread (Replacement) – The rubber or patch material used to make repairs. cords (plies). between the base of the tread groove Repairing – Reconditioning of portions Bead Separation – A breakdown and the buffed surface. of tires injured by punctures, cuts, of the bond between components Vulcanization – A chemical reaction breaks, cracks, etc. These repairs restore in the bead area. which takes place under appropriate strength for additional safe service Belt Edge Separation – A breakdown time, temperature and pressure and (See Reinforcement, Spot, Sections, Nail Holes). of the bond between components develops desirable characteristics and Retreading (Recapping) near the edge of the belt plies. properties. (See Cure) Full Treading – Replacement of the Shoulder – The upper sidewall areas of Weather Checking – Tire sidewall worn tread with rubber extending the tire casing immediately adjacent to surface crazing or cracking attributable over the shoulders. the tread area. to aging and atmospheric conditions rather than to flexing. Top Treading – Replacement of the Sidewall – That portion of the tire casing worn tread area only. between the tread and bead. Wicking – A capillary action caused by fabrics or cords that allows air to escape Bead-To-Bead Retreading – Skive – Removal of damaged material from the tire casing or from under Replacement of the worn tread area prior to making a repair. an envelope. and sidewall rubber extending to the bead.

91 Retreading S ECTION E LEVEN

RETREAD PLANT INSPECTION CHECKLIST

PLANT: ______DATE: ______

INSPECTOR(S): ______

NOT ACCEPTABLE ACCEPTABLE COMMENTS Plant Image A. Appearance B. Space and layout C. Lighting D. Ventilation E. Production capacity F. Outside certification G. Material storage H. Evidence of training

Casing Inspection A. Lighting B. Dry casings C. Repairs removed D. Casing I.D./tracking

Casing Repairing A. Location and lighting B. Repair information/procedures C. Material shelf life dates D. Material storage E. Single brand materials F. Repair I.D. G. Tool RPMs

Buffing A. Buffed dimensions, profile B. Specification information C. Exposed cords finished D. Exposed cords cementing E. Texturize unbuffed areas F. Mold fit measurement G. Rasp condition/smoking H. Buff texture I. Handling, cleanliness

92 S ECTION E LEVEN Retreading

NOT ACCEPTABLE ACCEPTABLE COMMENTS After-Buff Preparation A. Holes/cuts probed B. Buzz-out limits – Bias – Radial C. Cement application D. Cement dry time E. Cement shelf life

Tread Application A. Buzz-outs filled B. Tread rubber manufacturer brand/grade C. Spliced tread rubber – 2 splices maximum – minimum 120˚ spacing D. Handling/cleanliness

Curing A. Thermocouple tests B. Controls: pressure, temperature, and time C. Air/steam leaks D. Tire storage–distortion free E. Staples in tread of tire only

Final Inspection A. Lighting B. Inspect on spreader C. Inspect hot D. Staples removed E. DOT serial number F. RAR identification

93 Miscellaneous S ECTION T WELVE

Miscellaneous

The following section explains the use of

chains on radial truck tires. Chain use is

designed to offer additional traction, providing

the chains and tires are matched appropriately

for size and fit. General precautions to tire

siping, dynamometer testing and mixing

radial and bias ply tires are also addressed.

Finally, this section explains the variances

in sound levels produced by radial truck

tires, and the conditions under which

truck noise occurs.

94 S ECTION T WELVE Miscellaneous

USE OF CHAINS ON RADIAL TRUCK TIRES TIRE SIPING The use of tire chains can be helpful Tire siping is a process of making On the other hand, siping is generally in providing additional traction in severe small knife-like slits in the tread rubber believed to detract from treadwear on lug weather conditions (such as ice and heavy surface. Normally this is accomplished type tires used on drive-wheel position. snow) especially when traveling in hilly by a machine that uses sharp, highspeed This is because siping tends to break up or mountainous terrain. Tire chains can be rotating discs to make cuts that are at an the tread pattern and cause increased used safely and successfully with Goodyear angle of 90° to the circumference of the bending of the tread elements. This radial truck tires provided several simple tread. Siping cuts are normally controlled results in faster wear due to increased and important points are followed. so they are spaced a specific distance scuffing as the tire goes through its Always select chains that are specifically apart from one another. They also will footprint under torque. designed for radial tires. These chains vary in depth across the tread face. The effect tread siping has on tire normally have shorter cross chains than Proponents of tread siping have claimed performance can vary considerably with older designs and allow the position of various performance improvements for the particular tire pattern being siped. the side chains to be higher on the tire truck tires. These claims include improved For example, in a heavily bladed tread sidewall. This is out of the high-flex treadwear and reduced irregular wear. pattern it is believed that siping in the sidewall area of a radial tire and results Also, it is often claimed that siping original tread state could hurt treadwear. in less susceptibility to sidewall damage. improves traction for winter and wet Other tread patterns, such as those Be sure to use the proper chain size driving conditions on certain road types. having a much higher net-to-gross for the tire on which it is being attached. At present, the majority of truck tire footprint area, might be more adaptable Tighten chains when they are first siping is done in the westernmost for siping under the service conditions applied, then after a short run-in period, Midwest states and the Northwest discussed earlier. readjust to ensure a continued snug fit corridor. It is popular in certain areas, If a customer chooses to sipe his on radial tires. Serious sidewall damage and especially during the winter months, Goodyear tires, we strongly recommend may result from loose chains. to sipe both steer and drive, and that he pay close attention to the type of Check for adequate dual spacing, sometimes trailer tires. siping used. Specifically, our experience especially if using single tire chains on Goodyear’s position on siping is that is that siping should be performed laterally each tire of a dual assembly. The greater it may, under certain operating conditions, across the tread, although angles that deflection of the radial tire may require improve tire performance. However, vary somewhat from this might also be more dual spacing in marginally-spaced under the vast majority of truck operating acceptable. However, to the best of our dual assemblies. conditions, new tires are designed and knowledge, siping that is more or less Finally, always remove chains as soon produced with tread patterns and tread circumferential has not been demonstrated as they are no longer needed. compounds that do not require tread to be successful. Also, our experience siping to give satisfactory performance. shows that siping with varying depth Actual testing indicates that siping across the face of the tread usually may improve the tire’s resistance to yields better results than constant depth irregular wear on free-rolling wheel siping. This also appears to provide the positions that are susceptible to irregular minimum risk for increasing the tire’s wear due to the combination of operating susceptibility to tread rubber chunking. service and tire application. Specifically, It is important to note that the siping may help reduce irregular wear Goodyear warranty provides protection on trailer axles where light, one-way for the user against failures from loads are encountered, such as grain workmanship or material conditions. trailers or belly dumps that operate If a tire failure occurs because of a under extreme load variations from condition beyond Goodyear’s control, unloaded to loaded conditions. such as siping, the warranty is null and void.

95 Miscellaneous S ECTION T WELVE

DYNAMOMETER MIXING RADIAL TESTS AND BIAS PLY TIRES In recent years, a number of retread Dynamometers are used by truck Due to differences in cornering force rubber manufacturers have produced manufacturers, and frequently by truck characteristics and spring rates, the best precure tread rubber that is siped when distributors or large fleet operators, to test tire and vehicle performance will be molded. Various claims of improved the engines and other parts of the driveline. obtained by applying tires of the same treadwear, fuel economy, etc, have been Dynamometer rolls vary in size from size and construction (radial ply/bias ply) made. Our experience indicates that 8-5/8-inch to 50-inches. The smaller rolls to all vehicle wheel positions. However, while these claims may be true in specific have a greater potential for damaging different tire constructions are permitted instances, it is largely a matter of siping the tires. on the steer, drive, and trailer axles of the tread in such a way that is compatible During a dynamometer check, there two-axle, tandem, and multiple-axle with the particular tread rubber compound is little weight on the tires and only a combinations when the following rules and tread pattern design being used. In small area of the tread face (usually the are observed. other words, if tread siping is considered center rib or center portion of the tread) • Never mix different tire sizes or tire an integral part of the manufacture of is in contact with the roll. Excessive constructions on the same axle. new tread rubber at the outset, the siping heat builds up in this small area. If the • If radial tires are mixed with bias can be more or less customized to the test runs too long, the excessive heat tires, the best handling will be type of rubber and type of pattern so can damage the tire to the point where obtained with the bias tires on that performance can be optimized. it could fail later on the highway. the steer axle. In summary, tire siping may have The maximum safe time for running • Bias or radial tires may be used certain performance advantages in tires on a dynamometer roll varies with on either axle of two-axle vehicles, improved treadwear and/or traction; the roll diameter, speed, the power or providing the vehicle has dual rear however, these can be expected to vary torque transmitted from the tire to the wheels or is equipped with Super considerably, depending on the particular roll, and, to some extent, the load and Single wide-base tires. type of tread rubber, the tread pattern, inflation. Figure 12.1 shows general • Either bias or radial tires may be and the service conditions in which the rules for limiting the time for maximum used on the steering axle of vehicles tire is used. A customer considering power testing. with three or more axles. Either all siping tires should consult the new tire bias or all radial tires should be used or retread rubber manufacturer to discuss 50 – 60 MPH – Time Limit on the nonsteering axles. appropriate siping machinery and at Max Power • Never mix bias and radial tires in a Roll Dia techniques for the individual situation. tandem or multiple axle combination. 8 5/8'' 3 Min Always check with the vehicle manufac- 18'' - 20'' 5 Min turer before changing tire size or con- 30'' - 36'' 10 Min struction on any vehicle. Carefully 48'' - 50'' 15 Min evaluate performance changes caused by tire size or construction changes before Figure 12.1 putting the vehicle back into service.

For 50 percent power, the time can be doubled. For 25 percent power, the time can be quadrupled.

96 S ECTION T WELVE Miscellaneous

NOISE Tires are one source of noise emitted 400 Bias Ply Sound Level = 20 LOG10 Measured Sound Pressure by a truck operating at speeds above 35 Reference Sound Pressure Production MPH on a highway. In addition to the Cross Rib tires, other major sources of noise are: Note: • Engine The reference pressure is usually taken as the 300 • Radiator fan sound pressure at the threshold of hearing: the • Engine exhaust quietest sound that can be heard, 0.0002 microbar • Engine air intake of pressure. • Driveline • Aerodynamics (wind noise) Noise is defined as a disagreeable 200 sound. Pressure waves in the air produce Radial Cross Bias Ply sound. The human ear is designed to sense Rib these pressure waves and transmit signals Radial to the brain indicating the magnitude Rib and characteristics of the sound. 100 The ear mechanism can detect very 68 70 72 74 76 78 80 faint sounds with very low air pressure Sound Level Decibels (A) energy levels and yet can detect and withstand relatively loud sounds with Figure 12.2 Relative sound pressure vs. sound level in dB(A) from SAE J57 tests. high energy levels without becoming damaged. To accomplish this wide range Sound level units are measured in The data for the curve were obtained of hearing, the ear mechanism/brain decibels, abbreviated dB. Since the from standard SAE J57 tests using a truck response is not directly proportional to human ear does not respond the same with four test tires on drive axle and two the sound pressure, but is less sensitive for all frequencies of sound, the sound rib tires on steer axle. The test consisted at the louder end of the range. level meter has been modified to agree of a 50-mph coast-by with microphone The total noise output of a truck is closely with the frequency response of at 50 feet from the line of travel. usually measured with an instrument the human auditory system. When the When several sources cause sound called a sound level meter. The input frequency adjustments are included, the waves to impinge on the ear to the sound level meter is through a suffix (A) is added to the dB unit: dB(A). simultaneously, the ear perceives the microphone that is placed nominally The relationship of sound pressure to sum total of sound air pressure on the 50 feet from the center of the highway sound level in the region caused by the ear drum; the pressures are additive. lane that is being monitored. tires of a truck is shown in a relative However, the sound level perceived by The sound level meter has electronic fashion by the curve in Figure 12.2. the overall auditory system is increased circuitry designed to approximate the Note the relative increase in noise, only according to the logarithmic rule human auditory system. Thus, the input going from the relatively non-aggressive demonstrated by the curve. is varying air pressure caused by the radial rib tire to the bias ply rib tire; to Therefore, when sounds are emitted by sound — through a microphone — and the radial cross rib; to the bias ply cross various sources in a truck, the combined the output is a value indicated on a scale rib tire. effect can be obtained by adding sound that gives the sound level of the noise. Also note the nature of the curve pressures and then converting the total The sound level or more precisely, wherein greater changes in sound pressure sound pressure to dB(A). If individual the sound pressure level, indicates the are required to cause a given change in sources of sound have already been degree of loudness to the human ear of sound level at the higher sound pressures computed or measured in dB(A), the a given sound. than at the lower sound pressures. combinations of these sounds in terms of dB(A) cannot be obtained by addition of the individual dB(A) values.

97 Miscellaneous S ECTION T WELVE

Typical sound levels of various Since the enactment of the Noise For trucks of 1986 model year over-the-road truck components and Control Act of 1972, the EPA has been manufacture and later, the standard the effect on total sound level of empowered to issue regulations controlling requires that the external noise level combining these noise sources are the operational noise levels of interstate values must not exceed: shown in Figure 12.3. The tire noise rail and common carriers, and the noise • 87 dB(A) on highways at speeds value listed assumes the use of eight bias emissions of newly manufactured products. greater than 35 mph ply cross-rib drive tires on the truck. To do this, the EPA must identify a certain • 83 dB(A) on highways at speeds area of commercial endeavor or a certain of 35 mph or less Speeds Above 35 MPH – product as a “major noise source.” It then Six Predominant Noise Sources • 85 dB(A) during stationary runup has the authority to pursue regulatory at governed engine rpm Engine 80 activity to control and monitor that area New medium and heavy duty trucks or product. Early on, the railroads, airports, 82 (vehicles with GVWR of 10,000 lbs. Fan 79 certain manufacturing operations, and a or greater) must meet noise emission host of other activities were identified as 86 standards based on a vehicle acceleration Exhaust 80 major noise sources in need of regulatory and pass-by test at speeds of up to attention. The Agency specifically 83 but not exceeding 35 mph. The noise Intake 80 labeled medium and heavy trucks as measurement is taken at a distance of 87-90 significant sources of environmental dB(A) 50 feet from the centerline of vehicle Driveline 83 noise and has set up standards for the travel, and the test is performed by testing and control of the “total vehicle the vehicle manufacturer himself and Tires 75-86 noise emission package.” These standards, certified to the EPA. For medium and known as the Interstate Motor Carrier heavy duty trucks produced prior to Noise Emission Standards, are contained Figure 12.3 Combining noise sources. January 1, 1988, manufacturers had to in Volume 40, Parts 202 and 205, of the test their vehicles to a maximum external Typical methods used to reduce truck Code of Federal Regulations. They have noise level of 83 dB(A). For trucks noise to meet limits prescribed by law been in force since 1975, and apply to manufactured after January 1, 1988, the are as follows: all vehicles in over-the-highway service maximum external noise level permitted as well as to newly manufactured vehicles. • Reduce speed is 80 dB(A). • Retrofit equipment They set definite limits for total noise • Improve maintenance levels at various speeds and under • Remove irregularly worn tires stationary conditions. • Restrict lug tires to drive axles The legislation for in-service interstate • Use radial tires on all axles motor carriers requires that overall • Use rib tires on all axles external noise levels for trucks • 87-90 dB(A) manufactured previous to the 1986 model year not exceed the following Laws on noise are established by the values, measured at a distance of 50 feet Federal government, and are administered from the vehicle centerline: by the Environmental Protection Agency (EPA). Active enforcement, however, • 90 dB(A) on highways at speeds generally is the responsibility of state greater than 35 mph highway authorities. • 86 dB(A) on highways at speeds of 35 mph or less • 88 dB(A) during stationary runup at governed engine rpm

98 S ECTION T WELVE Miscellaneous

TIRE STORAGE RECOMMENDATIONS For Tires Not Installed 4. Undue Stress in Storage electrical sources and cut down on air on Vehicles If possible, tires should be stored circulation which will minimize both vertically on treads. Severely stressed the available oxygen and ozone which 1. Oil, Solvents and Grease and distorted tires are subject to much degrade rubber. Mounted or unmounted tires should greater damage from solvent, ozone or 8. Do Not Use Paint to Preserve Tires never be stored on oily floors or otherwise oxidative attack than those which are in contact with solvents, oil or grease. not stressed or are stressed minimally Nor should tires be stored in the same or and uniformly. Unmounted tires stacked For Tires Installed adjoining rooms with volatile solvents. horizontally (on sidewall) should be on Vehicles These solids, liquids or vapors are readily piled symmetrically and never so high as 1. The storage area surface under each absorbed in rubber and will damage and to cause severe distortion to the bottom vehicle should be firm, reasonably weaken it. tire. Tires that are mounted on rims but level, well drained and free of all oil, fuel or grease. Clean 1/4'' - 3/4'' 2. Ozone not on vehicles should follow the same gravel under each tire is desirable if Mounted and unmounted tires should recommendations as for unmounted tires. the area is not paved. Storage should be stored away from electrical devices 5. Foreign Material - Dirt, Water not be permitted on blacktop or oil such as motors, generators, arc welders Unmounted tires should be stored stabilized surfaces. and switches because they are active under a waterproof covering. Dirt is not 2. When storage longer than 6 months sources of ozone. Ozone attacks rubber harmful to a tire. However, dirt on the is anticipated, the vehicle should be causing it to crack perpendicular to any inside of a tire placed in service can blocked up so weight does not rest applied stress. Such cracking exposes the cause early tube failure or a slow leak. on the tires and inflation pressure new rubber surface at the base of the crack Water on the inside of a tire in service reduced to 15 PSI. Storage of such to greater stress and consequently to can be turned into steam which can vehicles should be under cover if more severe ozone attack until eventually quickly destroy the strength of both the possible. Otherwise, tires should the cracks can penetrate to the carcass rubber and the textile members of the be protected from elements by an where continued rubber degradation tire. Additionally, water and dirt inside opaque waterproof covering. could cause carcass failure. Minor, ozone a tubeless tire can cause corrosion to 3. If it is not possible to block up the induced, surface cracks will seldom cause tubeless rims and plug tubeless values, vehicle, inflation pressure in the tires tire failure, but can form an access route both a source of potential tire failure. should be increased to 25% above the for foreign material to penetrate the Foreign material on the tire bead seat inflation required for the actual load carcass once the tire is placed in service. could affect air seal and cause air loss. on the tire in the storage condition. 3. Heat and Light 6. Inflation 4. Vehicles should not be moved during Tires should be stored in a cool place, If tires are mounted on rims and extremely cold weather. Under away from direct sunlight or strong inflated, pressure should be maintained moderate temperature conditions, artificial light. Both heat and light are at 10 PSI. If tires are inflated and put in vehicles may be moved if necessary. sources of oxidation of the tire surfaces. storage during warm weather, the initial 5. Inflation in the tires must be adjusted The oxidation is characterized by a inflation should be about 15 PSI to offset to the recommended service pressure “crazed” or “alligatored” surface which the drop in pressure which will occur before shipping or putting a stored does not penetrate the rubber deeply. during the cold weather months. vehicle into service. The severity of the oxidation is, of course, 6. Both tires and vehicles should be used a time- and temperature-dependent 7. Protective Cover on a first-in, first-out basis to avoid variable. Long term storage at ambient If tires are stacked, first lay a foundation excessive aging due to storage. temperatures have been equated to short of clean wood to protect them from dirt, 7. Based on varying weather conditions, term storage at elevated temperatures. oil, grease, etc. Tires should be covered if tires are stored uncovered on For instance, three days storage at 158˚ F with an opaque or black polyethylene vehicles under load, some weathering causes approximately the same loss in film. PVC or any other clear film is not may occur at approximately one year tensile strength as three years storage at satisfactory. The polyethylene film will storage period. 75˚ F. Oxidation may cause sufficient protect against ozone generated by damage to the inside of an unmounted tire as to cause early tube failure or a slow leak.

99 Miscellaneous S ECTION T WELVE

WHEN DOES THE WARRANTY END

A tire has delivered its full original tread life and this warranty ends when the tread wear indicators become visible, or five (5) years from he date of original tire manufacture or original new tire purchase date (whichever comes first). How Do I Know When My Tires Were Maufactured? Tires with a Department of Transportation (DOT) number ending with 0100 or later were manufactured after 1/1/2000. 0100 is the 4-digit production date in week-week-year-year format. 0100 means the tire was produced in the 1st week of 2000. Prior to January 2000, a 3-digit date code was used following a week-week-year format. thus, 019 means the tire was produced in the 1st week of 1999.

TIRE SEALANTS AND BALANCE MATERIALS

There are many vendors that sell aftermarket tire sealants and balance materials that can be added or pumped into a tire. Goodyear does not endorse any product, but if you wish to use such a product as either a sealant or tire balancer, the Goodyear warranty is voided if the material adversely affects the tire inner liner.

100 Standards & S ECTION T HIRTEEN Regulations

Standards & Regulations

Both truck tire manufacturers and truck tire

users are covered by a number of federal and

state regulations designed to assure the safety

of the motoring public. Some of the more

important requirements of these regulations

are discussed in the following section, including

Federal Motor Carrier Safety Regulations,

Commercial Vehicle Safety Alliance and

Regrooving/Tire Siping Regulations.

101 Standards & Regulations S ECTION T HIRTEEN

FEDERAL MOTOR VEHICLE SAFETY STANDARDS TESTING AND CERTIFICATION The federal regulations which pertain The regulations encompassed by the to the performance and safety of truck Federal Motor Vehicle Safety Standards Federal Motor Carrier tires fall generally into two categories. for newly manufactured products are Those regulations which affect the testing, administered by the National Highway certification, and marking of newly Traffic Safety Administration (NHTSA), SAFETY manufactured tires are contained in Volume a branch of the U. S. Department of 49 of the Code of Federal Regulations Transportation (DOT). Those laws REGULATIONS (CFR), Part 571, and are referred to as contained within the Federal Motor “Federal Motor Vehicle Safety Standards.” Carrier Safety Regulations are administered TITLE 49 CODE OF FEDERAL REGULATIONS PARTS 40, 325, 383, 385, 386, 387, 390–397, 399 Those which cover over-the-highway by the Federal Highway Administration usage and application are contained in (FHWA), also a branch of the DOT, and U.S. DEPARTMENT OF TRANSPORTATION Volume 49 of the same Code, but in Parts enforced by the Bureau of Motor Carrier FEDERAL HIGHWAY ADMINISTRATION 350 through 399, and are called “Federal Safety (BMCS), a sub-agency of the FHWA Motor Carrier Safety Regulations.” and one of the few true enforcement SEPTEMBER, 1993 The differentiation between newly arms within the DOT. manufactured items and over-the-highway Part 571.119 of Volume 49 of the usage is quite clear. Thus, a tire Code of Federal Regulations, known as manufacturer is concerned with complying Federal Motor Vehicle Safety Standard American Trucking Associations with the Motor Vehicle Safety Standards 119 (FMVSS 119), requires that a variety regarding testing, certification and of tests be performed by a tire manufacturer markings, while the owner or operator to certify that a specific size of a tire line SUBPART G — MISCELLANEOUS of a vehicle who is using the tires in meets Federal safety requirements. The PARTS AND ACCESSORIES service must be in compliance with the main purpose of this law is to ensure Motor Carrier Safety Standards in regard tire testing and certification to specific §393.75 Tires. to the application, usage and condition performance parameters in the areas of (a) No motor vehicle shall be operat- of those tires. endurance and strength. By randomly ed on any tire that (1) has body ply or Standard 119 makes demands beyond sampling and laboratory testing tires in belt material exposed through the tread simply testing. For one thing, the tire must this manner during production periods, or sidewall, (2) has any tread or sidewall carry a serial code of up to eleven digits or a tire manufacturer certifies that his separation, (3) is flat or has an audible characters on one sidewall indicating the product meets the minimum safety leak, or (4) has a cut to the extent that name of the manufacturer, the producing requirements established by law. He also the ply or belt material is exposed. plant, the tire size, the tire type (brand properly qualifies his tires to carry the (b) Any tire on the front wheels of a name, load range, sidewall description, “DOT” stamping on the sidewall. Since bus, truck, or truck tractor shall have a etc.), and the week and year of production. this DOT marking must appear on any tread groove pattern depth of at least This information becomes especially tire legally sold for over-the- highway 4/32 of an inch when measured at any important for record keeping and recall use in the U.S., it becomes essential for a point on a major tread groove. The work. For another, the tire must carry manufacturer to test and certify his tires measurements shall not be made where information clearly molded into the to Motor Vehicle Safety Standard 119. tie bars, humps, or fillets are located. sidewall to give the consumer a variety The other Federal Motor Vehicle (c) Except as provided in paragraph of facts about the product, such as size, Safety Standard which effects truck tires (b) of this section, tires shall have a type, load range, generic names of materials, is FMVSS 120, which spells out tire and tread groove pattern depth of at least construction type, whether for single or rim selection and matching requirements 2/32 of an inch when measured in a dual usage, maximum load and inflation for vehicle manufacturers. This standard major tread groove. The measurement data, and of course the DOT symbol and is intended to ensure that when a consumer shall not be made where tie bars, humps serial code. The manufacturer must also purchases a new vehicle, the total maximum or fillets are located. include treadwear indicators evenly load capacities on any axle are at least as (d) No bus shall be operated with spaced around the circumference of the great as the gross weight rating of that regrooved, recapped or retreaded tires tire to indicate visually when the tire has axle, so that the load carrying capacity on the front wheels. worn to a tread depth of 2/32''. of the tires is not exceeded so long as (e) No truck or truck tractor shall be the vehicle is properly loaded. operated with regrooved tires on the

102 Standards & S ECTION T HIRTEEN Regulations

INSPECTION front wheels which have a load carrying A regular program of tire inspection is capacity equal to or greater than that of essential for the prevention of rapid air 8.25-20 8 ply-rating tires. loss failures. At a minimum, tires should (f) Tire loading restrictions (except on be inspected at the time of the regular manufactured homes). No motor vehicle preventive maintenance checks. (except manufactured homes, which are The Bureau of Motor Carrier Safety governed by paragraph (g) of this sec- recommends an inspection by the driver tion) shall be operated with tires that prior to every trip in its “Truck Driver’s carry a weight greater than that marked Pre-trip Check List.” on the sidewall of the tire or, in the In any tire inspection routine, tires absence of such a marking, a weight should be inspected for the following greater than that specified for the tires in conditions. If any are found, the tire any of the publications of any of the should be removed and repaired, retreaded organizations listed in Federal Motor or scrapped as the condition indicates. Vehicle Safety Standard No. 119 (49 • Any blister, bump or raised portion CFR 571.119, S5.1(b)) anywhere on the surface of the tire unless: tread or sidewall (other than a bump (1) The vehicle is being operated made by a repair). These indicate under the terms of a special permit the start of internal separation. issued by the State; and • Any cut that reaches to the belt or (2) The vehicle is being operated at a sidewall of the tire or, in the absence of ply cords, or any cut that is large reduced speed to compensate for the tire such a marking, the load rating specified enough to grow in size and depth. loading in excess of the manufacturer's in any of the publications of any of the • Any nail or puncturing object. rated capacity for the tire. In no case shall organizations listed in FMVSS No. 119 • If any stone or object is held by a the speed exceed 80 km/hr (50 mph). (49 CFR 571.119, S5.1(b)). tread groove and is starting to drill (g)(1) Tire loading restrictions for (h) Tire inflation pressure. (1) No into the tread base, remove the object. manufactured homes built before motor vehicle shall be operated on a tire • Look for skid spots and irregular wear January 1, 2002. Manufactured homes which has a cold inflation pressure less conditions and refer to the chapter on that are labeled pursuant to 24 CFR than that specified for the load being alignment, irregular wear, and rotation. 3282.362(c)(2)(i) before January 1, 2002, carried. The owner or operator should also be must not be transported on tires that are (2) If the inflation pressure of the tire aware that the use of recapped, retreaded, loaded more than 18 percent over the has been increased by heat because of or regrooved tires is restricted by the load rating marked on the sidewall of the the recent operation of the vehicle, the BMCS, Federal Motor Carrier Safety tire or, in the absence of such a marking, cold inflation pressure shall be estimated Regulations, and some state regulations, more than 18 percent over the load rating by subtracting the inflation buildup and that the Rubber Manufacturers specified in any of the publications of factor shown in Table 1 from the Association recommends against their any of the organizations listed in FMVSS measured inflation pressure. use in certain applications. No. 119 (49 CFR 571.119, S5.1(b)). In addition to the routine type of Manufactured homes labeled before Table I — Inflation pressure measurement correction common-sense, owner-performed tire January 1, 2002, transported on tires for heat inspection just described, there are overloaded by 9 percent or more must mandatory inspections which involve not be operated at speeds exceeding 80 Minimum inflation pressure buildup agents and agencies of the federal km/hr (50 mph). government. For example, the inspection (2) Tire loading restrictions for manu- Average speed Tires with Tires with over of tires for defects is required by NHTSA factured homes built on or after January of tire in 4,000 lbs. 4,000 lb. Vehicle In Use Inspection Standards, 1, 2002. Manufactured homes that are previous hour (1,814 kg) (1,814 kg) and by BMCS, Federal Motor Carrier labeled pursuant to 24 CFR 3282.362 maximum load load rating Safety Regulations. (c)(2)(i) on or after January 1, 2002, rating or less Part 396 of the Federal Motor Carrier must not be transported on tires loaded 41 to 55 mph 5 psi 15 psi Safety Regulations authorizes special beyond the load rating marked on the (66 to 88.5 (34.5 kPa) (103.4 kPa) agent personnel of the Federal Highway km/hr)

103 Standards & Regulations S ECTION T HIRTEEN

COMMERCIAL VEHICLE MINIMUM SAFETY ALLIANCE TREAD DEPTHS (CVSA) Administration, including Bureau of Under FMCSR Part 393.75, operators Motor Safety inspectors, to perform are required to maintain at least 4/32'' of inspections of a motor carrier’s vehicles tread groove depth on the front tires of which are currently in operation. These any bus, truck, or truck tractor covered inspections may be performed at a facili- by that law, and the standard 2/32'' ty of the motor carrier (such as a termi- remaining tread depth on the other nal) or at some other location (such as wheel positions. on-highway) at the discretion of the In conjunction with the federally inspector. The results of these inspec- required tire inspections previously tions are recorded in a Driver-Equipment mentioned, much work has been done Compliance Check report. If the check to promote commonly performed and is done at a location other than one of recognized tire inspection criteria within the motor carrier’s facilities, the driver is the scope of the total vehicle inspection required to deliver this report to the program in use by the Commercial motor carrier upon his arrival at the car- Minimum tread groove depths are Vehicle Safety Alliance (CVSA). rier’s next terminal, or to mail it to the specified for tire manufacturers under The CVSA is a voluntary organization carrier if he is not scheduled to be in a Federal Motor Vehicle Safety Standard made up of states and provinces which terminal within 24 hours after the time of 119, and for in-use applications by have responsibility for commercial vehicle the inspection. The motor carrier then Federal Motor Carrier Safety Regulations, safety operations and which perform has 15 days from the inspection date to part 393.75. Under FMVSS 119, vehicle inspections and conduct other correct any violations or defects, certify manufacturers must include tread depth safety related programs. The aims of any action taken using Form MCS-63, indicators, commonly called “wear bars”, the organization are to maximize the and return the form to the BMCS office in six locations evenly spaced around utilization of commercial vehicle, driver address indicated on the report. the circumference of a highway truck and cargo inspection resources, to avoid Part 397 of the same regulation tire, so that they become visible when duplication of effort, to expand the requires that for the transport of haz- 2/32'' of tread groove depth is remaining. number of inspections performed on a ardous materials, vehicles equipped with regional basis, to advance uniformity of duals on any axle must have the tires inspection, and to minimize delays in inspected every two hours or 100 miles, industry schedules which could result whichever occurs first, for the duration from this type of enforcement activity. of the trip. The CVSA does not supersede or countermand any legally required inspection process or any state laws. It is simply a working agreement among member jurisdictions to use standardized procedures. It has gained widespread acceptance and has made great progress toward providing a common inspection program. CVSA members inspect vehicles on-highway and in terminals. Areas covered by a CVSA vehicle inspection are the driver (license, hours-of-service records, medical certificate), steering mechanism, brakes, brake lights/turn signals, drawbars, suspension, fifth wheels, air loss and warning, wheels and tires. Vehicles which pass the inspection are issued a CVSA decal, colored differently for each quarter of the year, and honored for the month of issuance plus the

104 Standards & S ECTION T HIRTEEN Regulations

REGROOVING/ TIRE SIPING following two months by all participating Drive/Trail Tires Out of Service Regrooving is used in certain types of states and provinces. • 75 percent or more tread width loose service to extend the mileage obtainable Criteria for the tire inspection portion or missing, in excess of 12 inches of from the original tire tread. Tires designed of the CVSA inspection program tire’s circumference. with sufficient undertread depth to permit recommends replacement of a tire • Less than 1/32 inch tread depth at two regrooving are labeled on the sidewalls with any of the following conditions: adjacent, major tread grooves at three as regroovable. Undertread depth refers separate locations on tire. With duals, to the thickness of tread compound Steering Axle of Power Unit both tires must have listed defect to between the bottom of the original tread • Less than 2/32-inch tread depth at warrant out-of-service judgement. grooves and the top of the uppermost breaker or belt. The use of regrooving is two, adjacent, major tread grooves • Tire flat or has leak that can be felt more common in intra-state bus service anywhere on the tire. or heard. than in trucking fleets. • Portion of breaker strip or casing ply • Bias-ply tire with more than one ply Goodyear recommends retreading visibe in tread. exposed in tread area or sidewall, or radial tires for truck use rather than • Sidewall is cut, worn, or damaged when exposed area of top ply exceeds regrooving. If retreading is not practical, thereby exposing ply cord. 2 square inches. With duals, both tires front tires can be regrooved and moved • Labeled “Not for Highway Use” must have listed defect to warrant to trailers. Drive tires should be taken or other marking excluding current out-of-service judfgement. off when about 80 percent worn, the application (Excluding farm/ • Radial tire with two or more plies non-skid depth increased by regrooving, off-road vehicles briefly on the road. exposed in tread area, or damaged and then reapplied to the drive axle. • Bulge suggesting tread/sidewall cords evident in sidewall or exposed Regrooving requires probing the depth separation. Exception: Bulge from section area on sidewall exceeding 2 square of the undertread so that a minimum repair (sometimes identified by adjacent blue, inches. With dual, both tires must undertread depth of 3/32 inch remain triangular label) is not a defect unless higher have listed defect to warrant out-of- below the newly cut groove. It is than 3/8 inch. service judgement recommended that the local Goodyear representative be contacted for information • Tire flat or has leak that’s felt • Bulge suggesting tread/sidewall if regrooving is being considered. or heard. separation. Exception: Bulge from section repair (sometimes identified by adjacent blue, • Mounted/inflated so tire contacts part triangular label) is not a defect unless higher Tire Siping For Traction of vehicle. than 3/8 inch. Adding tire siping to new or partially • Tire overloaded, including overload • Mounted or inflated so tire contacts worn rib tires for additional traction resulting from under-inflation. (as differentiated from regrooving worn Exception: Does not apply to special part of vehicle or in the case of a dual assembly, its mate. tread for additional mileage) is an permit vehicle operated at a speed low enough accepted practice for trucking fleets to compensate for underinflation. • Tire overloaded, including overload resulting from under-inflation. operating on and off the road. Exception: Does not apply to special permit Partially worn radial lug tires can vehicle operated at a speed low enough to also benefit from regrooving the tread compensate for underinflation. pattern down to 80% of the deepest portion of the original non-skid depth for added traction.

105 Standards & Regulations S ECTION T HIRTEEN

DOT Regulations On regrooves tires and leases them to own- (g) If the tire is siped by cutting the Regrooved Tire ers or operators of motor vehicles and tread surface without removing Purpose and Scope any person who regrooves his own tires rubber, the tire cord material shall for use on motor vehicles is considered not be damaged as a result of the This part sets forth the conditions to be a person delivering for introduc- siping process, and no sipe shall under which regrooved and regroovable tion into interstate commerce within the be deeper than the original or tires manufactured or regrooved after meaning of this part. retread groove depth. the effective date of the regulation may (2) A regrooved tire may be sold, be sold, offered for sale, introduced for (B) Siped regroovable tires. No person offered for sale, or introduced for sale or sale or delivered for introduction into shall sell, offer for sale, or introduce for delivered for introduction into interstate interstate commerce. sale or deliver for introduction into commerce only if it conforms to each of interstate commerce a regroovable tire Definitions the following requirements: that has been siped by cutting the tread (A) Regroovable tire means a tire, (a) The tire being regrooved shall surface without removing rubber if the either original tread or retread, designed be a regroovable tire; tire cord material is damaged as a result and constructed with sufficient tread (b) After regrooving, cord material of the siping process, or if the tire is material to permit renewal of the tread below the grooves shall have siped deeper than the original or retread pattern or the generaton of a new tread a protective covering of tread groove depth. patternin a manner which conforms to material at least 3/32 inch thick; this part. (c) After regrooving, the new grooves Labeling of (B) Regrooved tire means a tire, either generated into the tread material Regroovable Tires and any residual original molded original tread or retread, on which the Each tire designed and constructed tread groove which is at or below tread pattern has been renewed or a new for regrooving shall be labeled on both the new regrooved depth shall tread has been produced by cutting into sidewalls with the word “Regroovable” have a minimum of 90 linear the tread of a worn tire to a depth equal molded on or into the tire in raised or inches of tread edges per linear to or deeper than the molded original recessed letters 0.025 to 0.040 inch. The foot of the circumference; groove depth. word “Regroovable” shall be in letters (d) After regrooving, the new groove 0.38 to 0.50 inch in height and not less Applicability width generated into the tread than 4 inches and not more than 6 inches material shall be a minimum of (A) General. Except as provided in in length. The lettering shall be located 3/16 inch and a maximum of paragraph (B) of this section, this part in the sidewall of the tire between the 5/16 inch; applies to all motor vehicle regrooved maximum section width and the bead in (e) After regrooving, all new grooves or regroovable tires manufactured or an area which will not be obstructed by cut into the tread shall provide regrooved after the effective date the rim flange. of the regulation. unobstructed fluid escape See Page 102 (Subpart G - (B) Export. This part does not apply passages; and Miscellaneous Parts and Accessories) to regrooved or regroovable tires intended (f) After regrooving, the tire shall for the Federal Motor Carriers Safety solely for export and so labeled or tagged. not contain any of the following defects, as determined by a visual Regulatons regarding regrooved tires. Requirements examination of the tire either (A) Regrooved tires. (1) Except as per- mounted on the rim, or dismounted, mitted by paragraph (A)(2) of this sec- whichever is applicable: tion, no person shall sell, offer for sale, (i) Cracking which extends to or introduce or deliver for introduction the fabric. into interstate commerce regrooved tires (ii) Groove cracks or wear produced by removing rubber from the extending to the fabric, or surface of a worn tire tread to generate a (iii) Evidence of ply, tread or new tread pattern. Any person who sidewall separation.

106 LOAD RATINGS AND INFLATION DATA FOR RADIAL TRUCK TIRES Tubeless Tube Type Load Range Load Range Load Range Load Range Load Range Load Range Load Range Dual Tire Load Rating D E F G H J L 7.50R16LT 2140@65 2440@80 LT225/75R16 2150@65 2470@80 LT245/75R16 2381@65 2778@80 LT215/85R16 2150@65 2470@80 LT235/85R16 2381@65 2778@80 3415@110 8.75R16.5LT 2070@65 2360@80 9.50R16.5LT 2445@65 2790@80 8R17.5 2755@85 8.5R17.5 3085@90 9R17.5HC 8.25R15 3660@105 3970@110 5675@125* 10R17.5 4410@110 11R17.5HC 10.00R15TR 4430@95 4850@110 6395@125 8R19.5 2700@80 3375@110 9R22.5 8.25R20 3950@95 10R22.5 9.00R20 4875@100 5250@115 11R22.5 10.00R20 5750@105 5800@110 12R22.5 11.00R20 5780@95 6750@120 13R22.5 7160@125 12.00R20 7200@110 14.00R20 9610@105* 11R24.5 10.00R22 6000@105 6170@110 12R24.5 11.00R22 6720@110 11.00R24 7130@110 12.00R24 8100@110 215/75R17.5 4540@125* 225/70R19.5 3415@95 245/70R19.5 3875@85 4375@100 265/70R19.5 4750@105 255/70R22.5 5070@115 245/75R22.5 4410@110 265/75R22.5 4805@100 295/75R22.5 5675@100 6005@110 295/80R22.5 6610@115 315/80R22.5 7610@120 7750@120* 13/80R20 7160@110 285/75R24.5 5675@100 Single Tire Load Rating 7.50R16LT 2440@65 2780@80 LT225/75R16 2335@65 2680@80 LT245/75R16 2623@65 3042@80 LT215/85R16 2335@65 2680@80 LT235/85R16 2623@65 3042@80 3750@110 8.75R16.5LT 2350@65 2680@80 9.50R16.5LT 2780@65 3170@80 8R17.5 2835@85 8.5R17.5 3195@90 9R17.5HC 8.25R15 4070@105 4410@110 6005@125* 10R17.5 4675@110 11R17.5HC 10.00R15TR 5050@105 5530@120 6945@125 8R19.5 2800@80 3500@110 9R22.5 8.25R20 4500@105 10R22.5 9.00R20 5150@100 5680@115 11R22.5 10.00R20 6175@105 6610@120 12R22.5 11.00R20 6590@105 7390@120 13R22.5 8270@125 12.00R20 8210@120 14.00R20 10960@115* 11R24.5 10.00R22 6430@105 7030@120 12R24.5 11.00R22 7660@120 11.00R24 8130@120 12.00R24 9230@120 215/75R17.5 4805@125* 225/70R19.5 3640@95 245/70R19.5 4080@85 4545@100 265/70R19.5 5000@105 255/70R22.5 5510@115 245/75R22.5 4675@110 265/75R22.5 5205@110 295/75R22.5 6175@110 6610@120 295/80R22.5 7390@115 315/80R22.5 8270@120 9000@120* 13/80R20 8050@110 14/80R20 9090@120 365/80R20 10000@130 285/75R24.5 6175@110 385/65R22.5 9370@120 425/65R22.5 10500@110 445/65R22.5 12300@120 Notes: 1. With above loads and inflations, the maximum speed is 65 MPH. *55 MPH max. 2. For ML tires, see Tire and Rim Year Book for separate ML table.

107 TRUCK TYPE AND WEIGHT CLASS The vehicle icons on the following page depict examples of vehicles in each DOT classification 1-8 with corresponding load ranges. These classifications are guidelines in understanding the type of vehicle used for different applications by vehicle class.

CLASS ONE 6,000 lbs. or less Full Size Pickup Mini Pickup Minivan SUV Utility Van

CLASS TWO 6,001 to 10,000 lbs. Crew Size Pickup Full Size Pickup Mini Bus Minivan Step Van Utility Van

CLASS THREE 10,001 to 14,000 lbs. City Delivery Mini Bus Walk In

CLASS FOUR 14,001 to 16,000 lbs. City Delivery Conventional Van Landscape Utility Large Walk In

CLASS FIVE 16,001 to 19,500 lbs. Bucket City Delivery Large Walk In

CLASS SIX 19,501 to 26,000 lbs. Beverage Rack School Bus Single Axle Van Stake Body

CLASS SEVEN 26,001 to 33,000 lbs. City Transit Bus Furniture High Profile Semi Home Fuel Medium Semi Tractor

Refuse Tow

CLASS EIGHT 33,001 lbs. & over Cement Mixer Dump Fire Truck Fuel Heavy Refrigerated Van Semi Tractor

Semi Sleeper Tour Bus

TRAILERS

Auto Transport Double Van Drop Frame Dry Bulk Dump Trailer Flatbed

Flatbed Low Boy Logger Reefer Tanker Van Trailer

108 INDEX

Ackerman Steering Effect In-Service Alignment Recommendations..49 Retreading ...... 86 on Tire Wear...... 47 Inflation ...... 37 Definitions ...... 90 Alignment...... 43 Do’s and Don’ts for Maintaining Introduction...... 87 Ackerman Steering Effect on Proper Inflation Pressure...... 42 Planning A Retread Plant Visit ...... 87 Tire Wear ...... 47 Nitrogen Inflation ...... 42 Plant Inspection ...... 87 Camber...... 46 Underinflation ...... 40 Retread Plant Inspection Checklist ...... 92 Caster...... 46 Inspection...... 103 Safety Instructions...... 20 Drive Axle Alignment ...... 48 Inspection Procedures...... 31 Safety Precautions...... 28 In-Service Alignment Installation...... 23 Section Repair Limits in Sidewall and Shoulder Area...... 84 Recommendations ...... 49 Loaded vs. Unloaded Loaded vs. Unloaded Alignment Servicing Tire and Rim ...... 31 Alignment Settings...... 45 Setback Steer Axles...... 53 Settings...... 45 Lubrication ...... 20 Steer Axle Alignment ...... 45 Siping...... 95 Toe ...... 46 Matching of Duals ...... 25 Spacers...... 26 Trailer Axle Alignment...... 49 Minimum Tread Depths ...... 104 Spacing of Duals ...... 26 Mixing Radial and Bias Ply Tires...... 96 Speed and Tire Wear ...... 57 Bearing Adjustment...... 55 Mounting and Inflation ...... 29 Standards and Regulations ...... 101 Branding Tires ...... 35 Mounting Procedure...... 19 Commercial Vehicle Safety Alliance Camber...... 46 Assembly of Tire Tube Flap...... 22 (CVSA)...... 104 Caster...... 46 Demounting...... 24 Federal Motor Carrier Center-Over-Injury Section Repairs ...... 85 Inspection Procedures ...... 31 Safety Regulations ...... 102 Chains on Radial Truck Tires ...... 95 Installation...... 23 Federal Motor Vehicle Safety Standards Collecting and Storing Lubrication...... 20 Testing and Certification...... 102 Tire Information ...... 35 Matching of Duals...... 25 Inspection...... 103 Branding Tires...... 35 Mounting and Inflation ...... 29 Minimum Tread Depths ...... 104 Radio Frequency Operation ...... 31 Steer Axle Alignment...... 45 Identification Tags...... 36 Proper Matching of Rim Parts...... 27 Steer Tire Wear ...... 52 Radio Frequency Tag Usage...... 36 Safety Instructions...... 20 Tire and Rim Cleaning...... 21 Commercial Vehicle Safety Alliance Safety Precautions...... 28 Tire Description & Specifications...... 76 (CVSA)...... 104 Servicing Tire and Rim ...... 31 Tire Industry Definitions ...... 90 Cross-Sectional View of Typical Tire...... 6 Spacers...... 26 Tire Repairs...... 80 Crown Repair Limits...... 85 Spacing of Duals ...... 26 Application of Center-Over-Injury Section Repairs ...... 85 Demounting ...... 24 Tire and Rim Cleaning...... 21 Tubeless Tire Mounting ...... 23 Crown Repair Limits ...... 85 Drive Axle Alignment...... 48 Nail Hole Repair Procedures...... 82 Drive Tires...... 54 Tubes and Flaps...... 22 Wheel Inspection Guidelines...... 20 Radial Ply Tires ...... 85 Dynamometer Tests...... 96 Radial Tire Section Repairs ...... 84 Factors Affecting Treadwear...... 50 Nail Hole Repair Procedures...... 82 Radial Tires ...... 84 Bearing Adjustment...... 55 Nitrogen Inflation...... 42 Radial Section Repair Limits...... 84 Drive Tires ...... 54 Noise...... 97 Section Repair Limits in Environmental Effects...... 56 Operation ...... 31 Sidewall and Shoulder Area...... 84 Tire Sealants And Balance Materials ....100 How Speed Affects Tire Wear...... 57 Planning A Retread Plant Visit...... 87 Setback Steer Axles...... 53 Tire Selection & Maintenance ...... 70 Plant Inspection ...... 87 Tire Selection Process ...... 9 Steer Tire Wear...... 52 Proper Matching of Rim Parts...... 27 Factors Affecting Truck Fuel Economy..63 Tire Selection Process Work Sheet...... 16 Appendix ...... 78 Radial Ply Tires...... 85 Tire Siping/Regrooving...... 105 Environmental Conditions...... 74 Radial Tire Section Repairs...... 84 Tire Siping for Traction...... 105 Summary...... 77 Radial Tires ...... 84 DOT Regulations on Regrooved Tire ...... 106 Tire Description and Specifications...... 76 Radial Section Repair Limits ...... 84 Labeling of Regroovable Tires...... 106 Tire Selection and Maintenance ...... 70 Radial Truck Tire Terms...... 5 Toe ...... 46 Vehicle and Engine Design...... 64 Cross-Sectional View of Typical Tire ...... 6 Trailer Axle Alignment...... 49 Vehicle Operation ...... 67 Radio Frequency Identification Tags...... 36 Tube Flap Assembly ...... 22 Federal Motor Carrier Radio Frequency Tag Usage...... 36 Tubeless Tire Mounting ...... 23 Safety Regulations...... 102 Regrooving/Tire Siping...... 105 Tubes and Flaps ...... 22 Federal Motor Vehicle Safety Standards Tire Siping for Traction...... 105 Underinflation...... 40 Testing and Certification...... 102 DOT Regulations on Regrooved Tire ...... 106 Labeling of Regroovable Tires...... 106 Vehicle and Engine Design ...... 64 Retread Plant Inspection Checklist...... 92 Vehicle Operation...... 67 Wheel Inspection Guidelines...... 20 109 www.goodyear.com/truck

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