Tabulated Data

TABLE OF CONTENTS

VOLUME I

A. VERTICAL LOAD VS. CHANGE IN ROLLING HEIGHT ...1 11 -00 - 22/G (90 PSI) 12.00 - 20/G (80 PSI) 15.00 - 22.5/H (90 PSI) CAMBER STIFFNESS VS. TIRE LOAD ...... 3 CORNERING STIFFNESS VS. TIRE LOAD. ..3 CIRCUMFERENTIAL STIFFNESS VS. TIRE LOAD...... 3 LATERAL SPRING RATE VS. TIRE LOAD...... 3 11.00 - 2216 (90 PSI) 12.00 - 20/G (80 PSI) 15.00 - 22.5/H (90 PSI) LATERAL SPRING RATE VS. INFLATION PRESSURE ..... 3 TABULATED DATA ...... 5 Circumferential Stiffness Cornering Stiffness Camber Stiffness Lateral Spring Rate Vertical Spring Rate For 9.00 - 20 E 9.00 - 20 F 10.00 - 20 F 10.00 - 20 G 17.00 - 22 F 11.00 - 22 G B. FX/FZ VS. FZ/FZ-RATED ON ASPHALT .....7 FXIFZ VS. VERTICAL LOAD ON ASPHALT ...... 8 FX/FZ VS. VELOCITY ON ASPHALT. ...:...... 9 FX/FZ VS. TEST RUNS ON ASPHALT ...... 10 Firestone Transport I 10-20/F 8 100 PSI Goodyear Superhimiler 10-20/F @ 100 PSI General Power Jet 10-2O/F @ 100 PSI Goodyear Superhimi 1 er 11-22.5/F @ 100 PSI Firestone Transport I 12-20/H @ 120 PSI Uniroyal Unimaster Rib 15-22.5/l-1

I Research Injiiibt..Fl"" ILP 1 FX/FZ VS. NORMALIZED LOAD ON ASPHALT & CONCRET

FXIFZ VS. VELOCITY ON ASPHALT & CONCRETE . . . . , . 12 Firestone Transport I 10.00 x 20/F Goodyear Super Hi Miler 10.00 x 20/F FX/FZ VS. ASTM SKID NUMBER ...... 13 Firestone Transport I 10.00 x 20/F Goodyear Super Hi MIler 10.00 x 20/F

C. FXIFZ VS. VELOCITY ON DRY ASPHALT @ 0.5, 1.0 ?I 1.5 x RATED LOAD ...... 15

FX/FZ VS. FZ/FZ-RATED ON WET JENNITE @ 20 MPH. . . . 17

FX/FZ VS. FZ/FZ-RATED @ 40 MPH ...... 17 10 x 20/F on Asphalt 15 x 22.5/H on Concrete 10 x 20lF on Concrete FX/FZ VS. VELOCITY @ RATED LOAD...... 17 10 x 20/F Asphalt 10 x 20/F Concrete 15 x 22.5/H Concrete FX/FZ VS. FZ/FZ0RATED @ 85 PSI & 50 PSI...... 18

On Dry Asphalt 60 MPH Dry Asphalt 40 MPH Wet Jennite 20 MPH

E. TABULATED RESULTS...... , ...... 19-20 Fx/Fz vs. Fz on Wet Jennite @ 20 MPH on Dry Asphalt @ 40 MPH on Dry Asphalt @ 60 MPH F. CORNERING STIFFNESS VS. VERTICAL LOAD . . , , . , . 21 FX/FZ VS. PERCENT SLIP @ 40 MPH & RATED LOAD. ... 22 FX/FZ VS. FZ/FZ RATED @ 20 MPH, 40 MPH, & 55 MPH. 23-25

Uniroyal Fleetmaster Super-Lug Firestone Transport 200 Goodyear Super Hi Miler General GTX Firestone Transport I Goodyear Custom Cross Rib TABULATED DATA ...... 26 Peak and Slide Values of Fx/Fz Goodyear Super Hi Miler Firestone Transport 200 Firestone Transport I Goodyear Custom Cross Rib General GTX Uniroyal Fleetrnaster Super-Lug

FY/FZ VS. SLIP ANGLE @ 20, 40, & 55 MPH; RATED LOAD. 27

FYIFZ VS. SLIP ANGLE @ 0.5, 1.0 & 1.5 X RATED LOAD; 20 MPH FOR THE SAME 6 TIRES IN THIS REFERENCE MA- TERIAL...... 28 TABULAR FLAT-BED TEST RESULTS FOR THE SIX TIRES. ..29 Vertical Load Lateral Force @ Slip Angle = -lo,0" & lo Cornering Stiffness G. TABULATED DATA ...... 30 Peak and Slide Values of Fx/Fz on -Wet Concrete Goodyear Super Hi Miler Firestone Transport 200 Firestone Transport I Goodyear Custom Cross Rib General GTX Uniroyal Fl eetmaster Super-Lug FX/FZ PEAK VALUES VS. VELOCITY 8 RATED LOAD. ....31 FX/FZ SLIDE VALUES VS. VELOCITY 8 RATED LOAD ...32 FX/FZ PEAK VALUES VS. FZ/FZ-RATED @ 55 MPH .....33 FX/FZ SLIDE VALUES VS. FZ/FZ-RATED @ 55 MPH. ..34 FY/FZ VS. SLIP ANGLE @ 40 MPH, 0.5 x RATED LOAD . . -35 FY/FZ VS. SLIP ANGLE 8 55 MPH, 1.0 x RATED LOAD ON -WET CONCRETE FOR THE FOLLOWING TIRES . .36 Firestone Transport I General GTX Goodyear Super Hi Miler Firestone Transport 200 Goodyear Custom Cross Rib Uniroyal Fleetmaster Super-Lug

Uniroyal Triple Tread (10 x 20/F) B.F. Goodrich Milesaver Radial Steel H.D.R.- (10R20G) B.F. Goodrich Milesaver Radial Steel H.D.B.- (10R20G) Goodyear Unisteel R-1 (10R20G) Firestone Power Drive (10 x 20/F) Uniroyal Fleetmaster Super-Lug (10 x 20/F) Firestone Hiway Mileage (12.5 x 22.5 G) Michelin Radial XZA (llR20H) Michelin Radial XZA (11R 22.5 H) FX/FZ VS. FZ/FZ-RATED @ 20, 40 & 55 MPH .....38-40 Firestone Hiway Mileage (12.5 x 22.5G) Michelin Radial XZA (llR20H) Michelin Radial XZA (llR22.5H) FX/FZ VS. FZ/FZ-RATED @ 20, 40, & 55 MPH. ....41-43 Goodyear Unisteel R-1 (10R20G) Uniroyal Triple Tread (10 x 20/F) B.F. Goodrich Radial Steel H.D.R. (10R20G) Firestone Power Drive (10 x 20F) B.F. Goodrich Milesaver Radial H.D.B. (10R20G)

FY/FZ VS. SLIP ANGLE @ 20 MPH; 0.5 & 1.5 RATED LOAD ...... 44-45 FY/FZ VS. SLIP ANGLE @ RATED LOAD; 20, 40 & 55MPH...... 46-48 Firestone Hiway Mileage (12.5 x 22.56) Michelin Radial XZA (12R 22.5H) Firestone Power Drive (10 x 20F) B.F. Goodrich Milesaver Radial Steel H.D.R.- (10R20G) FY/FZ VS. SLIP ANGLE @ RATED LOAD; 20, 40 & 55MPH ...... 49-51

Goodyear Custom Hi Miler (8.75 x 16.5 E) Firestone Transport 500 (8.00 x 16.5D) Goodyear Custom ~lexsteel(8.00R 16.5E) Goodyear Super Singje Hi Miler (10.00 x 16.5E) Michelin Radial XCA (8.00R 16.5 E) Firestone Town & Country Truck (8.00 x 16.5D)

FY VS. SLIP ANGLE @ LOAD = 2050 LB...... 53 Firestone Transport 500 (8.00 x 16.5D) Michelin Radial XCA (8.00R 16.5 E) General Jumbo Power Jet (8.00 x 16.5D) CORNERING STIFFNESS VS. FZ ...... 55 Uniroyal Triple Tread 10 x 20 F B.F. Goodrich Milesaver Radial Steel H.D.R.- 10R20G Goodyear Unisteel R-1 1OR20G & Others ... CORNERING STIFFNESS VS. FZ ...... 57 Firestone Hiway Mileage 12.5 x 22.5 G Michelin Radial XZA llR20H Michelin Radial XZA 11R 22.5 H 1. CORNERING STIFFNESS VS. VERTICAL LOAD...... 59 FXIFZ VS. VELOCITY @ RATED LOAD ON -DRY CONCRETE. ..60 FXIFZ VS. FZIFZ-RATED 8 20 MPH ON -DRY CONCRETE ...61 FX/FZ VS. VELOCITY @ RATED LOAD ON -WET CONCRETE. . 62 FX/FZ VS. FZ/FZ-RATED 8 20 MPH ON -WET CONCRETE ...63 FOR THE FOLLOWING 10R20G TIRES Firestone Transteel Firestone Transteel Traction Goodyear Uni steel R-1 Goodyear Unisteel L-1 Michelin XZA Michelin XZZ TABULATED DATA ...... 65 Peak and Slide Values of FxlFz On Both Dry & -Wet Surfaces Firestone Transteel Goodyear Unisteel R-1 Michelin XZA Firestone Transteel Traction Goodyear Unisteel L-1 Michelin XZZ FYIFZ VS. SLIP ANGLE

i) 20 MPH; 1.5 x Rated Load on Dry Concrete. .66 ii) 55 MPH; Rated Load on Dry Concrete. . .67 iii) 20 MPH; 0.5 x Rated Load on Wet Concrete. .68 iv) 55 MPH; Rated Load on Wet Concrete. . .69 !I, NORMALIZING LONGITUDINAL FORCE VS. VERTICAL LOAD . . -70 NORMALIZING LONGITUDINAL FORCE VS. VELOCITY...... 70 10.00 x 20/F--3 Different Manufacturers 11 x 22.5/F 12.00 x 20/H 15 x 22.5/H NORMALIZED LONGITUDINAL FORCE VS. VELOCITY .....-70 10 x 20/F--2 Different Manufacturers On Four Different Surfaces NORMALIZED SIDE FORCE VS. SLIP ANGLE ...... 70 @ 0.5 & 1.5 x Rated Load 10.00 x 20 Tires @ 32 km/hr Radial Ply, Rib Tread Bias Ply, Rib Tread Bias Ply, Lug Tread N. CORNERING STIFFNESS VS. VERTICAL LOAD...... 71 Bias Rib Tires Radial Rib Tires Bias Lug Tires Radial Lug Tires

FX/FZ VS. SPEED @ RATED LOAD ON & WET CONCRETE...... 72-73 FX/FZ VS. FZ/FZ RATED 8 20 MPH ON -DRY & WET CONCRETE...... -74-75 Goodyear Custom Cross Rib Uniroyal Fleetmaster Super-Lug Firestone Transport 200 Goodyear Super Hi Miler General GTX Firestone Transport I

FX/FZ PEAK & SLIDE VALUES VS. SPEED ...... 76-79 @ Rated Load on Dry & Wet Concrete NORMALIZED LATERAL FORCE FY/FZ VS. SLIP ANGLE . . 80-81 @ Rated Load, 55 MPH on Dry & -Wet Concrete Radial Rib & Lus" Bias Rib & Lug 0. CORNERING STIFFNESS VS. NORMAL LOAD . .92 12.5 x 22.5G @ 100 PSI 10.0 x 20.0F @ 100 PSI 8.75 x 16.5E @ 75 PSI 8.0 x 16.5D @ 75 PSI Q. GRAPHICAL COMPARISONS ...... 85-90 Locked Wheel Braking Force Coefficient on Concrete Peak Braking Force Coefficient on Concrete Peak Lateral Force Coefficient on Concrete Locked Wheel Braking Force Coefficient on Asphalt Peak Braking Force Coefficient on Asphalt Peak Lateral Force Coefficient on Asphalt TABULATED SUMMARY FOR THE ABOVE ...... 91-92 CORRELATION BETWEEN TRACTION PROPERTIES ...... 93 STANDARD DEVIATION BETWEEN PAIRS OF TIRES .....,94 COMPARISON OF TRACTION PROPERTIES ...... 95-96 On a Smooth Concrete Pavement On a Coarse Asphalt Pavement TABULATED DATA ...... , . 97 Lateral Force vs. Inflation Pressure, Load, Steer Angle Aligning Moment vs. Inflation Pressure, Load, Steer Angle Firestone Transport 110 I. TABULATED DATA

Lateral Force vs. Inflation Pressure, Load & Steer Angle Aligning Moment vs. Inflation Pressure, Load & Steer Angle

For the Following Tires Firestone Transport WO ...98 Goodyear Rib Himiler ...... 99 Firestone Town & Country Truck ...... 100 Goodrich Milesaver Radial Steel HDR ...101 Goodyear Glas Guard XG ...,102 General Jumbo Power Jet Commercial . ,103 Goodyear Glas Guard. . .I04 GRAPHICAL REPRESENTATION & TABULATED DATA. ...105-194 Fy vs. Slip Angle & Normal Force Fy vs. Slip Angle, Fz & Velocity Normalized Tractive Force vs. Time Elapsed Lateral Force vs. Sl i p .Angle All for Firestone 8 80 PSI

DYNAMOMETER

Fy/Fz vs. Slip Angle & Fz @ 40 MPH - 1-9-76 ...... I95 Fy/Fz vs. Slip Angle & Velocity @ 2865 LB - 1-9-76 ...... I96 Fy vs. Slip Angle & Repeated Runs 8 2844 LB, 40 MPH - 1-9-76 ...... ,197 Firestone Transport 500 Wide Oval Fy/Fz vs. Slip Angle & Fz 8 40 MPH - 10-21-75 ...... I98 Fy/Fz vs. Slip Angle & Velocity 8 2771 LB - 10-17-75 .....I99 Fy vs. Slip Angle & Repeated Runs 8 2787, 41 MPH - 10-17-75 ...200 Firestone Transport 500 on Asphalt

Fy/Fz vs. Slip Angle & Fz I3 40 MPH - 1-9-76 ...... ,201 Fy/Fz vs. Slip Angle & Velocity @ 2804 LB - 1-9-76 ...,202 Fy vs . Slip Angle & Repeated Runs @ 2801 10. 40 MPH . 1-9-76 ...203 Firestone Town & Country Truck Fy/Fz vs . Slip Angle & Fz @ 41 MPH . 1-9-76 ...... 204 Fy/Fz vs . Slip Angle & Velocity @ 2843 LB . 1-9-76 ....205 Fy vs . Slip Angle & Repeated Runs @ 2832 LB. 41 MPH . 1-9-76 .....206 General Jumbo Power Jet I. TABULATED DATA

Lateral Force vs. Inflation Pressure, Load, Steer Angle Aligning Moment vs. Inflation Pressure, Load, Steer Angle Goodyear Custom Flexsteel ...207 Michelin Radial XCA ...208 DYNAMOMETER Fy/Fz vs. Slip Angle & Fz 8 40 MPH - 1-9-76 ...... ,209 FylFz vs. Slip Angle & Velocity 8 3025 LB - 1-9-76 ...... 210 Fy vs. Slip Angle & Repeated Runs 8 3026 LB, 41 MPH- 1-9-76. . . . 211 Goodyear Custom Flexsteel Fy/Fz vs. Slip Angle & Fz @ 41 MPH - 1-13-76...... 212 FylFz vs. Slip Angle & Velocity @ 3077 LB - 1-13-76 ...... 213 Fy vs. Slip Angle & Repeated Runs @ 3084 LB, 41 MPH - 1-13-76 ...... 214 Michelin XCA A. TABULATED SUMMARY OF MECHANICAL PROPERTIES @ 65 PSI ...... 215 Circumferential Stiffness Cornering Stiffness Camber Stiffness Lateral Spring Rate Vertical Spring Rate TABULATED DATE & GRAPH ...... ,215 Lateral Force vs. Inflation Pressure CORNERING STIFFNESS VS. TIRE LOAD @ 65 PSI ....,215 CAMBER STIFFNESS VS. TIRE LOAD @ 65 PSI ...215 TABULATED DATA ON COMPARISON OF TIRE ALIGNING MOMENT @ 65 PSI ...... ,215 R. TABULATED DATA ...... ,217-218 Vertical Load Inflation Pressure Lateral Force @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Aligning Torque @ 1,2,4,8,12 & 16' Slip Angle Vertical Load Inflation Pressure Circumferential Stiffness Vertical Spring Rate Highway Tread - Single & Dual E. FX/FZ VS. LONGITUDINAL SLIP, VELOCITY & FZ . . .219-227 Uniroyal Fleetmaster on Wet Jennite TABULATED DATA ...... ,228 Vertical Load Inflation Pressure Lateral Force @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Aligning Torque @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Circumferential Stiffness Vertical Spring Rate Highway Tread I. DYNAMOMETER Fy/Fz vs. Slip Angle & Fz @ 40 MPH - 1-9-76...... ,229 FylFz vs. Slip Angle & Velocity @ 2846 LB - 1-9-76 ...... 230 Fy vs. Slip Angle & Repeated Runs @ 2832 LB, 40 MPH - 1-9-76 ...,231 Goodyear Super Hi-Miler Wide Tread Fy/Fz vs. Slip Angle & Fz @ 39 MPH - 10-21 -75 ...... ,231.1 Fy/ Fz vs. Slip Angle & Velocity @ 3268 LB - 10-17-75 ....,232 Fy vs. Slip Angle & Repeated Runs @ 3314 LB, 40 MPH - 10-21 -75 . ,233 Goodyear Hi-Miler Wide Tread Fy/Fz vs. Slip Angle & Fz @ 41 MPH - 1-9-76 ...... ,234 Fy/Fz vs. Slip Angle & Velocity @ 2915 LB - 1-9-76 ...... 235 Fy vs. Slip Angle & Repeated Runs @ 2945 LB, 41 MPH - 1-9-76 ...... 236 Goodyear Glas-Guard XG

FY/FZ VS. SLIP ANGLE @ RATED LOAD, 20 MPH, 40 MPH, 55 MPH ...... 237-239 Goodyear Custom Himiler

TABULATED DATA

Lateral Force vs. Inflation Pressure, Load, Steer Angle Aligning Moment vs. Inflation Pressure, Load, Steer Angle

For the Following Tires: Goodyear Super Himiler .... .240 Goodyear Glas Guard XG .....241 Firestone Town & Country Truck ,242 Goodyear Custom Flexsteel. . .243 Michelin Radial XCA ...244 General Jumbo Power Jet Commercial ...245 Goodyear Glas Guard ...246 Goodyear Rib Himiler Wide Tread.247 A. TABULATED DATA FOR FOLLOWING MECHANICAL PROPERTIES (E & F) ...... ,248 Circumferential Stiffness Cornering Stiffness Camber Stiffness Lateral Spring Rate Vertical Spring Rate

L. FX/FZ VS. LONGITUDINAL SLIP @ 60 MPH ON DRY ASPHALT ...... 249 Uniroyal Fl eetmaster [9-20/E] E. DYNAMOMETER Fx/Fz vs. Longitudinal Slip ...... ,257-258 Uniroyal Fleetmaster (9-20/E) on Wet & Dry Surfaces @ Various Combinations of Fz & Velocity R. TABULATED DATA Vertical Load Inflation Pressure Lateral Force @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Aligning Torque @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Circumferential Stiffness Vertical Spring Rate Highway Tread (9-20/E) ...... 259 Vertical Load Inflation Pressure Lateral Force @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Aligning Torque @ 1,2,4,8,12 & 16" Slip Angle Vertical Load Inflation Pressure Circumferential Stiffness Vertical Spring Rate Highway Tread (9-20/F) . ,260 TABULATED DATA . , ...... , . . . . . ,261 Lateral Force vs. Inflation Pressure, Load, Steer Angle Aligning Moment vs. Inflation Pressure, Load, Steer Angle

Montgomery Wards Steel Belted Super Wide I. TABULATED DATE FOR GOODYEAR SUPER SINGLE HIMILER. . 262 Lateral Force vs. Inflation Pressure, Load & Steer Angle Aligning Moment vs. Inflation Pressure, Load & Steer Angle

FY/FZ VS. SLIP ANGLE @ 20, 40, 55 MPH & RATED LOAD ...... ,263-265 Goodyear Super Single Himiler

DYNAMOMETER FylFz vs. Slip Angle & Fz 8 41 MPH - 1-9-76 .,...... ,266 Fy/Fz vs. Slip Angle & Velocity @ 2984 LB - 1-9-76 ....267 Fy vs. Slip Angle & Repeated Runs @ 2980 LB, 41 MPH - 1-9-76 ...... 268 Goodyear Super Single Himiler loads, the tire behaves (laterally) like a softening spring. The / = 1 locked wheel lateral spring rate is the slope through the origin of the lateral s = 0 free roiling (light braking: s < 0.05) load-deflection curve. < 0 driving TRACTIOY STIFFNESS (C,. C,,, Cs) - The following three F, = longitudinal traction force (depends primarily on s) properties are defined to characterize the mechanical behavior Fy = lateral traction force (depends on both a and y) of a rolling tire operated at very small siip and camber angles and for very light application of bra~ingor driving power. Graphically, the traction stiffness is the slope taken through Cornering Stiffness the origin of the traction force (F, or Fy) versus a particular operating variable (a. y, or s) curve. These stiffnesses measure the initial rise of traction force and have no direct relation to ( 1) peak values. However, a tire with higher traction stiffness will usually develop higher peak traction force. The usefulness of ,. these definitions depends on linear behavior for small values of Camber Stiffness the operating variables. Examination of the following truck tire data will show thls linearity to be a reasonable assump-

(21 GENERAL BEHAVIOR

Circumferential Stiffness Figs. 2A-2C describe three truck tires chosen to exhibit a broad range of traction stiffness properties*. The mechanical properties listed below each tire were measured at rated load and pressure. The carpet plots of lateral force versus slip angle (3) and vertical load show the variation in lateral force obtained and indicate how the cornering stiffness, C,, is related to slip where: angle and load. Although C, measures only the initial rise of lateral force with slip angle for a particular tire load. the rise is a = slip angle similar at orher tire loads. It appears that a tire showing y = camber angle higher cornering stiffness will develop more lateral force than = s circumferential slip parameter a lower stiffness tire operated at the same slip angle and vertical load.

:' 1/ J\; / TIRE LOAD

j',j. - The operating variable having the greatest influence on traction stiffness is tire load. The influence of tire load derives

3 ,". . from the extreme deformation which a tire undergoes in the contact region. Specifically, the meridian and circumference profiles, intersecting at the center of contact, are substantially - ...,I3 - altered in dimension and curvature as tire load is increased. The camber, cornering, and circumferential stiffnesses. being indirectly influenced by lateral and longitudinal tire stiffness, "JJO - are consequently dependent on structural geometry, and are seen to increase with test load for the tires diagrammed in . ~, :, .'> - Figs. 3A-3D. Particularly affected by sidewall deformation is the lateral spring rate, 5. Fig. 3D illustrates the variation of 5 with 4d'!) - tire load for the three tires shown in Figs. 2A-2C. Increasing load on the tire from far below the design value results mainly 3.100 - in an increased contact length with some change in the meridian profile. The increased contact length causes an in- 1:.:19-:-,8; YO ?,, crease in lateral stiffness. At higher loads, the changes in tire :130 , , , - II~SIC,, 4 : Change .n Rali.na: tielynt .n Fig. 1 -Vertical load versus change in low-speed rolling height of tires *The tires are representative of the 14 different truck tire shown in Figs. 2A-ZC sizes tested for ths program. 85 PSI Zero Camber

Load 6140 lb.

CS 51,000 lblunit slio Ca 536.9 lb/deq

a0 PSI Zero Camb

Load 6140 lb. Cs 60,000 lb/unit Slin

90 PSI Zero Camber

Load 8640 lb. C, 85,000 Ib/unit sl

Fig. 2 - Measured mechanical properties of three different tires. A-1 1.00. piofile become very pronounced, especially in the sidewall higher loads which cause large distortions in the meridian area, and cause a reduction in spring rate. It should be noted profile. that the maximum value of lateral spring rate occurs near the The cornering stiffness, Ca, exhibits similar pressure sen- design load for each tire tested. sitivity at higher vertical loads. Fig. 5 compares the lateral The vertical load-deflection data are remarkably linear for a force versus slip angle and vertical load exhibited by a broad range of tire loads (Fig. 1). Fig. 1 suggests that it is 10.00-2O/G tire (Fig. 6B) at rated inflation pressure (100 reasonable to consider the tire as a linear vertical spring with psi) and at 50 psi. can be anticipated from lateral spring spring rate, KZ,defined as the average slope of the load- rate behavior measured for these three different tires (Fig. deflection plot. 4), cornering stiffness increases with inflation pressure at higher loads. INFLATION PRESSURE The apparent similarity between K, and C, is due to the definition of K, as the lateral stiffness of a standing tire mea- Increasing inflation pressure reverses the deformation caused sured at, effect;vely, a 0 deg $lip angle while C-+ is defined t~ by vertical load. Although a decrease in contact length ac- measure the stiffness of the rolling tire in generating lateral companies an increase in inflation pressure, the dominant effects of increased pressure are reduced curvature in the side- force at very small slip angles. However, the contact regon wall and a generally stiffened carcass structure. The net result deformation associated with tire traction is considerably more complicated than the deformation associated with the mea- is a lateral spring rate that increases with inflation pressure, as surement of K . As no rational basis exists for the correlation is demonstrated by Fig. 4; these data being obtained on the Y three tires shown in Figs. ?A-2C. As may be expected, the of these values, they are treated as independent mechanical effect of increasing the pressure is more pronounced at the properties.

10,oo s lb/unit slip , 12.00- (80 PS '0,OO 12.00-2OIG (80 psi)

11.00-22/G (90 psi)

I Tire Load (lb) Tire Load (lb) I I 20 1 1 I I I I C :,do0 J,:OO 6,d00 8,000 10,000

12.00-2OlG 180 pslj

11.00-!2iG 11.00-22lG 'YO ?Sl, (90 psi)

1600 12.00-!O/G (80 psi)

300- Tire Load (lb) /' 1200 T~reLoad 115) I 1 I 1 I 2000 4000 5000 8000 :0000 :002 I I I I I a Design Load - D Fig. 3 - Variation of mechanical properties with tire load for tires shown in Figs. 2A-2C. A-camber stiffness versus tire load: B-cornering stiffness versus tire load; C-circumferential stiffness versus tire load; D-lateral spring rate versus tire load 'LY RATING AND TIRE SIZE near the design values specified for these tires used as singles and duals. The higher rated tire of each pair is generally used ,t':::.::.-.- The ply rating designates the load range for which a particu- as a dual. The 20 in tires that were tested dl have the tread wci; ar size tire is designed. Load limits for various sizes at specific pattern shown in Fig. 6B. The tread pattern of the 11.00-22 nflation pressures up to the design pressure are tabulated tires (Fig. 2A) is similar. Table 2 lists the measured mechani- ~ccordingto empirical formulae. The ply rating is a measure cal properties and illustrates the differences which may be )f the strength of the tire carcass and does not necessarily found in tires which are similar in all respects, except for ply ndicate the actual number of plies. rating. The tire pairs listed in Table 1 were tested on design width The differences seen in Table 2 are slight and possibly in- recision rims at the indicated pressures and loads which are fluenced by tire nonunifomity and/or measurement precision. There is remarkably little change in the properties of the 11.W22 tires, the largest set tested for differences due to ply rating. The slight increase in test pressure (see Table 1) may i200 be responsible for the increases in vertical spring rate. It is of interest to note that the vertical spring rate measured for the iooo 10.0(120 tire with the G rating was less than that obtained for the F load rating. However, the lateral force generating ability leoo did increase with increased load rating as evidenced by the

:600

12.00-20/G (6140 lb)

0 00 11.00-22/C (6140 lb)

I I I a o 9 o 10o psi 'ig. 4 Lateral spring rate K versus inflation pressure for tires shown Y Fig. 5 - Lateral force versus slip angie and vertical load on 10.00-20/G I Figs. 2A-2C tire at rated pressure (100 psi) and at 50 psi

(a) Rlb-type I (b) Rib-type 11 (c) Open Tread 46000 42000 28000 508.2 523.4 516.0 56.7 69 .O 39.9

1477 1618 1291 lb/in Fig. 6 - Measured mechanical properties of 10.00-20/F nylon tire in three tread patterns. A- 5032 4700 4500 lb/in rib-type 1; B-rib-type 11; C-open tread measured increase in C, and by the carpet plot comparison is a result oi increased trendcompliance*. It would be of given in Fig. 7. ~onsiderableinterest to compare tlie peak braking traction of Fig. 7 represents the extreme in force variation found in this the rib-type and open tread tires. Although the force mea- . study of ply rating and tire size. More tests are needed to suring equipment employed in these tests was incapable of establish fimily the trends evident in Table 2. responding to a longitudinal slip much above s = 0.03**. the higher initial slope (indicated by the measured Cs) of the F, TREAD PATTERN INFLUENCE *This is to be expected in the open pattern which has ap- It is widely recognized that the tread pattern is a very im- proximately twice the void area of the closed rib-type pattern. portant factor in wet traction performance. However, it also **Far below that required for peak braking force generation. appears that pattern influence is noticeable in the data from low-speed dry-traction flat bed tests. Fig. 6 shows the three 10.00-20/F nylon tires, similar except for tread design, that were tested in this study. Listed beneath the tires are the five basic mechanical properties defined earlier. The values shown were measured at rated inflation pressure. 85 psi, and rated load. 5430 Ib. From an examination of the data, it appears that tread design has little influence on the tire spring rates Ky and KZ. The cornering stiffness. C,, was affected very little-although the open tread did generate slightly higher lateral force at higher slip angles than the rib-type pattern (see comparison presented in Fig. 8). The camber stiffness. $,was substantially changed by the tread pattern. In Fig. 9, it is seen Fig. 7 - Comparison of lateral force versus slip angle and vertical load that the open tread generated considerably less lateral force on 10.00-20 tires with ply ratings F and G (or camber thrust) than tlie rib-type pattern. The marked decrease in longitudinal stiffness, C, (Fig. 61,

-- -

Table 1 - Tires Tested to Determine Influence of Ply Rating and Tire Size on Mechanical Properties

Tire Test Test Size and Rating Pressure, psi Load, lb

9.00-?O/E 80 4160 9.00-20/F 85 4250 10.00-20/F 85 5430 10.00-20/G 85 5430 Fig. 8 - Lateral force versus slip angle and vertical load on open and 11 .OO-22/F 85 6290 rib-type I1 tread patterns 11.00-22/G 90 6140

', Table 2 - Measured Mechanical Properties for Three Sets 6f Two Tires Which Differ Only in Ply Rating

9.00-20 10.00-20 11.OO-22 Tire Rating ------E F F G F G C,, lblunit slip 41.000 41,000 42,000 50,000 47,000 51,000 Ca,lbldeg 466.1 479.4 523.4 588.8 542.7 536.9 C7,lbldeg 59.6 64.4 69.0 74.6 63.3 62.8 Kv, lblin 1,673 1,889 1,618 1,482 2,116 1,909 Kz, Ib/in 3,824 4.122 4.700 4,363 5,578 5,850 2.2 DATA MEASUREMENT AND PROCESSING PROCEDURES

2.2.1 TIRE PREPARATION. Truck tires were prepared for testing through the maintenance of certain practices intended to assure consistency of test conditions as well as repre- ' sentativeness of measured traction performance. All tires were mounted on their respective Tire 6 Rim Association- recommended rims (disc wheels). The inflation pressure of each tire was maintained at a representative "hot" inflation level which had been identified in prior testing as the equilibrium value which accompanies operation at 60 mph and rated load, following "cold" inflation to the TERA-recommended value. The maintained "hot" inflation pressure values are shown for each sample in Table 4.

Table 4. Maintained TEM-Recommended I1Hotv Tire Sample Size Code "Cold" Inflation Inflation Firestone 10.00x20/F FTlO 85 psi 100 psi Transport 1 Goodyear Super 10,0Ox20/F GySlO Hi Miler

General Power 10 ,OOx20/F GllJlO Jet Goodyear Super 11x22.5/F Hi Miler Firestone Transport 1 Uniroyal 15x22.5/H Unimas t er Rib Tire Codes -3-

El-. Tire Codes 0 FTlO

Vertical load, lbs x 103

Figure 17. Load sensitivity (non-normalized abscissa) in the peak and slide traction of the six-tire sample (on BADC asphalt). Tire Codes 0 FTlO C] GySlO A GIlJlO 0 GySll FT12 UUlS

I Velocity, MPH Figure 18. Velocity sensitivity of the peak and slide traction values for the six-tire sample (on BADC asphalt). Tire Code @ FTlO 0 GySlO A GllJlO C GySll @ FT12

Figure 19. Peak and slide traction measures deriving from reDeat runs of each of the six tires tested on thk asphalt track at BADC.

0 FTlO

h FTlO O PTlO i:ys1u

U1 0) 3 -m 5. Y

BADC Asphrlt TRC Asphalt

.-a >"

'-'

10 20 30 40 50 Velocity, MPH Velocity, MPH

Figure 25. The differing influence of pavement surface on the velocity sensitivities of two tires. ASTM Skid Number Figure 26. Correlation between the mean peak and slide values measured among the repeat runs of each of two tires and the respective SN40 measurements on each of four test pavements. 0 Dana Concrctc BADC Asphalt A TRC Asphalt 0 TRC Concrete

j * P' P *-- .--I- .- -, i! i! Test Runs

Figure 2-. Peak aad slide values deriving from repeat runs of tne Firestone Transport 1 (10,0Ox20/F) on four surfaces. 1.0 Un~royolFleetmaster 12-20/G Wet Jennlte, 20 mph 9 -

0' ,b i0 ;o ,b do 70 do gb do LONGITUDINAL SLIP, Percent Fig, 6 - Typical "p-slip" history measured on wet, jennite- coated surface

\SELINE DATA SUMMARY range over which the 15 x 22.5 tire could be tested, suf- ficient data was obtained to indicate significant differ- Shown in Fig. 7 is a summary of peak and slide values ences in normalized longitudinal force capability. Also F,/F, for the tire sample on the dry asphalt surface. shown in Fig. 9 are peak and slide values taken over a ie general load sensitivity of the subject sample is indi- somewhat narrower load range on asphalt, with the 10 x ted by the variation in performance over the three ex- 20 tire. While the peak values differ markedly in both ,nedload levels. expressed as a fraction of the T&RA 0 8.25-~O/E :ommended load for each tire. A two-point velocity 9-20/E nsitivity indicator is provided at each load level by the 10-~O/F 1 and 60 mph data. A 12-20/G 1.0- Fznst In general, the data are rather closely grouped, al- GZ~0.5 0 12-22.5/F ough the sample of tires was by no means representa- 8 15-22.5/H re of the range of constructions and rubber compounds Fz t..l ich are available. As can be deduced from the spread -.I.O Fz mid :tween the peak and slide values, peak-to-slide ratios are Fz test -3 1.5 gher at the lower velocity-since the peak F,/Fz data FZrated \ow a significant decrement with velocity in the 40-60 ph range while slide values are essentially unchanged. Shown in Fig. 8 is a summary of peak and slide F,/F, measured for an eight-tire sample on a wet jennite- 0.7 lated asphalt. These data, all taken at 20 mph, are pre- nted as a function of vertical load, normalized to the K" &RA rating of each tire. All of the sample tires in- Ka Values rporated a common highway rib tread design and thus 0.6 Sllde e might have anticipated the fairly consistent wet sur- Values ce performance indicated across the sample. Neverthe- ss, the remarkable tight grouping does suggest that the &RA load rating is a powerful normalizer. ENSITIVITY TO VERTICAL LOAD 0.4 -- Data taken over a wide range of vertical loads on dry mete (SN = 75) are shown in Fig. 9. For comparison f two tires of widely differing load rating, a 10 x 20/F I,- lmple is represented together with data from a 15 x 0'3dmpn 60m4 4Omph 6Omph 40mph mmqh 2.5/H wide base single tlre. Although the brake torque Fig. 7 - Summarv of F,/F, peak and slide data-dry asphalt, 40 and ipability of the mobile dynamometer limited the load 60 mph Uniroyol Fleetmoster 9-20/E Dry Asphalt. 60mph 0.91

LONGITUDINAL SLIP, Percem Fig. 5 Example of "r-slip" history measured on dry surface

break-in, the tire was operated at its rated load and at the Notable characteristics of the Fig. 5 example include a reference value of inflation pressure described above. force peak occurring in the vicinity of s = 20%, followed by a rather steep negative slope out to s 85%, at which DISCUSSION OF PRELIMINARY - point an abrupt inflection occurs, depressing the locked TRACTION MEASUREMENTS wheel value further. Over a sample of eight tires tested on -_ The mobile dynamometer described earlier has been a dry bituminous asphalt surface (SN = 78) the ratio of r""' operated under various conditions of test surface, veloc- pcak-to-slide F,/F, ranged from 1.50 to 2.02 with the ity, tire load, and tire samples to produce analog mea- force inflection $ the high slip regime being observed surements of the longitudinal traction of truck tires. over a majority of conditions. Comparing this general As indicated previously, the preliminary measurements curve shape with those commonly measured on dry sur- which are reported here involve longitudinal force data faces with passenger car tires, we observe that the truck which has been scaled using~steady-stateF, and h$ re- tire's narrow, accentuated peaking, followed by a 30-50% cording, Thus the interpretation of &solute values in the reduction in force capability at lockup contrasts mark- normalized longitudinal force measures is not encouraged, edly with the car tire's rather flat shape in the 20-100% since the torque scaling of Fx neglects that torque compo- slip range. nent which derives from the rearward deflection of the vertical load vector during generation of "braking" shear The typical p-slip curve shape which was measured forces. Although the data have been corrected to account with truck tires on a wet jennite-coated asphalt (SN = for this influence, per estimates based upon static laboratory 20) is shown in Fig. 6. In this case, the on-board water measurements of truck tires, we suggest that the presented delivery system was employed to deposit a water film of data have greatest merit as indicators of relative sensitivities. 0.025 in nominal thickness ahead of the test tire at 20 . While longitudinal force production has been found to be mph test velocity. (The film thickness dimension is de- sensitive to various operating conditions, the single property fined as the height of the rectangular cross section stream which most significantly distinguishes truck tires from auto- which is deposited on the test surface at the indicated mobile tires concerns the remarkable peakmto-slide ratios velocity.) which are exhibited on dry surfaces. As shown in Figure 5, The broad peak on the Fig. 6 curve is a characteristic the typical dry asphalt performance is summarized in the which was observed over all specimens in the eight-tire form of a "p.slip" history (a plot of normalized longitudinal sample. In most cases, the peak value of F,/F, is sus- force, Fx/F, versus the ratio of instantaneous tangential tire- tained to within 0.02 over a band of Iongitudinal slip V - R,w which is the excess of 40%. The peak-to-slide ratios on to-road relative velocities, s =- v x 100%) the wet-coated asphalt were seen to range from 1.53-2.02. Although the pronounced peak-to-slide decrement is where V = vehicle velocity comparable to passenger car tire performance on such a %= effective roiling radius of the test tire surface, the broad peak characteristic of the truck tire w = angular velocity of the test tire. sample is notable. IOKZOIF, Asphalt SlidePeak }

15 x22.5/H, Concrete

F,/F, Peak 0.4 iiN \

Fx/Fz Slide 0.2

0 00.5 1.0 1.5 2.0 F2 IFz,-ow NORMALIZED VERTICAL LOAD

Fz /Fz ratd Fig. 9 .Fx/F, sensitivity to vertical load at velocity = 40 mph Fig. 8 - Summary of Fx/Fzpeak and slide data-wet jennite, 20 mph

trend and absolute values, the slide data on both surfaces condition, with peak values of Fx/F, being influenced to a agree well over the common range of loads. much lesser extent. These data suggest that the load sensitivity of truck These dry surface data, in general, seem to indicate tires, in terms of longitudinal traction capability, is suf- that: truck tires can exhibit significant longitudinal trac- ficiently influenced by both surface pavement and tire tion sensitivity to velocity and that these sensitivities can design characteristics that generalizations are difficult. be markedly influenced by pavement characteristics.

SENSITIVITY TO VELOCITY A SlidePeak } lo I 20/F. Asphalt Data taken over a wide velocity range on both asphalt and concrete surfaces have indicated a significant sensitivity of peak and slide performance to velocities as shown in Fig. 10. Comparing surfaces, the 10 x 20 tire sample which was tested at its rated load of 5430 Ibs, indicated a markedly different behavior on an asphalt versus concrete pavement (although the respective ASTM skid numbers were 78 asphalt and 75 concrete). As shown, this tire indicates a large increase in both peak and slide values of Fx/F, in the low velocity regime on asphalt, while only the slide values appear to indicate a significant velocity sensitivity on the concrete surface. This phenomenon causes the peak-to-slide ratio on dry concrete to range from 1.75 at 60 mph down to 1.08 at 3 mph. Comparing two tires of widely differing load rating, the 10 x 20/F and 15 x 22.5/H are seen to exhibit comparable peak and slide behavior, over the 3-60 mph velocity 10 20 30 40 50 60 range. Both tires showed, on concrete, a dominant veloc- VELOCITY, mph ity sensitivity of shear force production at the 100% slip Fig. 10 - Fx/Fzsensitivity to velocity at F, = rated load INFLATION PRESSURE SENSITIVITY IMPLICATIONS OF THESE TEST RESULTS ON PREDICTIVE APPROACHES ...... *...... Shown in Fig. 11 is a sample of data taken on a 10 x v::::: ZO/F highway rib tire at two values of cold inflation pres- The truck tire data presented in this paper show several sure. The dry asphalt data show a significant decrease in characteristics which challenge currently available semi- peak force capability with decreased inflation pressure, empirical tire models (9). The phenomena which present while the slide values are much less influenced by the 85 the greatest challenge to modeling are: to 50 psi pressure reduction. Interestingly, the dry surface sensitivity of peak forces to inflation pressure is 1. The very broad maximum force region which was greatest at the lighter vertical loads, while on the wetted obtained on the wet jennite-coated surface. (The normal- surface, the least sensitivity of peak force to inflation ized force is nearly maximum over the range of 20%-60% pressure was found at the lightest load. slip. See Fig. 6)

TREAD WEAR SENSITIVITY 2. On dry surfaces the peak normalized force obtained for most of the tires tested decreased significantly be- A set of three 10.00 x 22/F tires was tested represent- tween the 40 and 60 mph cases but the lock wheel slide ing each of three tread wear conditions: new, half-worn, values are nearly equal at 40 and 60 mph. (See Fig.-. 7.) and fully worn. The fully worn condition of this highway 3. On dry surfaces the load and velocity sensitivities of rib tread was represented by a nominal depth of 1/8 in. the peak longitudinal force are highly dependent upon in the circumferential grooves, of which there were only pavement characteristics. Also, the measured level of two (kerfs and sipes were no longer evident at this wear peak longitudinal force can differ greatly between mea- condition). The data shown in Fig. 12 illustrate the antic: surements made on asphalt and concrete surfaces which ipated result of increasing dry traction and decreasing have equal skid numbers. (See Figs. 9 and 10,) wet traction with increasing wear. To the extent that groove depth nost significantly effects hydrodynamic Clearly, the measured peak and slide longitudinal force phenomena related to wet surface traction, however, the properties of truck tires depend upon normal load, veloc- largest influences are to be found at elevated velocities ity, and surface condition in a significant and complicated not represented in these data. manner. &;;:..

0 Dry Asphalt, 60 mph a Dry Asphalt. 40 mph 0 We? Jennlte, 20 mph

Dry Asphalt, 60 mph Dry Asphalt, 40 mph 50ps Inflation Wet Jennite, 20 mph 1

..... 'I::::::. (::::.':: (::::.':: : ......

11 I I I I I I 0.5 I .O 1.5 0.5 I .O 1.5 FZ 'Fz mted Fig. 11 - F,/F, sensitivity to inflation pressure TABLE 4 SUMMARY OF UXCORRECTED BASELINE DATA

20 mph 40 mph 60 mph Tire Wet Jennite Dry Asphalt 1 Dry Asphalt Fz p~ Z1s F z Y~ Us 1 kz Y~ Us I TABLE 5

SUMMARY OF BASELINE DATA CORRECTED PER TIIE TABLE 3 ERROR RANGE ESTIMATES

20 mph - Wet Jennite 40 mph - Dry Asphalt 60 mph - Dry Asphalt "P Irs IIi - - 1.0 Iii -- Lo FZ

2012 .83 --.78 .51 --.48 a Goodyear Custom Cross Rib

8 Uniroyal Fleet blaster Super Lug A Firestone Transport 200 A Goodyear Super Hi Miler

0 General GTX

p Firestone Transport 1

Figure 7. Cornering Stiffness, C,, as Influenced by Vertical Load, F,, for the Six-Tire Sample. 5

A Goodyear Super Hi 5 P Miler Firestone Transport 1 o General GTX r Firestone Transport LOO Fleet Master

0 0 2 5 SO 7 5 100 Percent Slip

Figure 9. Characteristic p-slip curve shapes at the reference condition of 40 mph and 1.0 x Rated Load. 1.0 -

0 . !I .-

0. 8 --

'I. 7 --

0 . 0 -- IJ 3 +4 9 -3 1.5 -- Goodycar Custom Cross Rib 4u lJ 3 m Uniroyal Flcct Master Super Lug 1.1 L \ A Fircstonc Transport 200 x 4 1.4 -- a Coodycar Super Hi Miler General (;'TX

1.3 -- 0 1:irestonc Transport 1

I I 1.2 I I I 0 0 . 5 1. 0 1.5 F /F z 'rated

Figure 10. Pcak and slide values of Fx/FZ at 20 mph for the six-tire sample. 1.0 -

3.9 =-

0.8 ==

0.7 *-

Slide '

I 0.6 --

, 0.5 --

I Goodyear Custom Cross Rib

I Uniroyal Fleet Master Super Lug F1 , x A Firestone Transport 200 , 0.4 -- A Goodyear Super Hi Miler

o General GTX

0,3 .- a Firestone Transport 1

I 0.2 I I 1 0 0.5 1.0 1.5 Fz/F 'rated Figure 11. Peak and slide values of Fx/F, at 40 mph for the six-tire sample. Slide

Goodyear Custom Cross Rib lUniroyal Fleet Master Super Lug

~FirestoneTransport 200

A Goodyear Super Hi Miler

0 General GTX

firest tone Transport 1

F'IF 'rated Figure 12. Peak and slide values of Fx/FZ at 55 mph for the six-tire sample. TABLE 4 PEAK AND SLIDE VALUES OF F /F AS OBTAINED OVER THE FIVE REPEAT RUN^ F~REACH OF THE SIX SAMPLE TIRES

Goodyear Super Hi Miler Firestone Transport 200 Run "P " s Run p~ ps

Avg. .856 ,608 Avg. ,746 .56 u .00800 :0117 u .0242 ,0167

Firestone Transport 1 Goodyear Custom Cross Rib Run "P "s Run "P ps

Avg. ,822 ,568 Avg. ,714 .548 u .0172 .00748 u ,0258 ,00980

General GTX Uniroyal Fleetmaster Super-Lug Run "P Run " s 1 .83 1 .70 .54 4 ,83 4 .71 .55 7 .83 7 .73 .55 10 .80 10 .74 .56 13 .82 13 .74 .55 Avg. ,822 Avg. .724 .55 a ,0117 u .01625 .00632 ALPHA (DEGREES) t Figure 15. Envelopes of Fy/Fz vs. a data obtained at test velocities of 20, 40, and 55 mph and at rated load for all six tires in the sample. .-• llniroyal Fleet Elaster Super Lug 4 Goodyear Custom Cross Rib - Firestone Transport 200 0-4 Firestone Transport 1 -4 General GTX - Goodyear Super Ili Miler

ALPHA (DEGRE €5) ALPHA (DEGREES) ALPHA (DEGREES)

Figure 16. Summary of the Py/I:, vs. a behavior of the six-tire sample at each of three loads, and at 20 mph. APPENDIX B-I

TABULAR FLAT-BED TEST RESULTS

The following table indicates lateral force measurements which were obtained with each tire at slip angles of +loand at 0" for each of three values of vertical load. The cornering stiffness parameter, C,, is then listed as the average of the lateral forces obtained at +loand -lo,

Lateral Force, lbs Cornering Vertical at Slip Angles, a Stiffness C, Tire Load, lbs. +lo -lo OO. lbs/deg Goodyear 16 30 -291 234 -31 263 Super Hi Miler 3260 -459 363 -60 411 5430 -606 444 -73 525

General

Firestone 1630 -346 267 -49 306 Transport 1 3260 -540 403 -76 471 5430 -670 486 -106 578

Uniroyal 16 30 -268 21'5 -26 242 Fleetmaster 3260 -430 340.- -47 385 Super Lug 5430 -559 417. s,-64 483

Goodye ar 1630 -270 224 -36 247 Custom Cross 3260 -433 337 -56 385 Rib 54 30 -572 418 -77 495

Firestone 16 30 -259 178 -30 219 Transport 200 3260 -403 289 -51 34 6 5430 -538 315 -84 426 Table 1, Peak .and Slide Values of Fx/FZ as Obtained Over the Five Repeat Runs for Each of the Six Sample Tires on Wet Concrete.

Goodyear Super Hi Miler Fires tone Transport 200 IJ Run !J P Run P lJ s

Avg. .674 ,448 Avg . ,646 ,488 u ,012 ,0204 Q .013 .0075

Fi restone Transport 1 Goodyear Custom Cross Rib v IJ Run P Run P s

Avg, ,780 ,574 Avg . ,608 ,462 u ,0179 ,0195 u ,0147 ,0117

General GTX Uni royal Flee tmas ter Super-Lug lJ lJ Run P !J s Run P s

Avg. .732 .518 Avg . ,516 .390 u ,0147 .a156 o .0262 .0261 i A Firestone Transport 1 0 General GTX a Goodyear Super Hi Miler A Firestone Transport 200 Q Goodyear Custom Cross Rib a Uniroyal Fleetmaster Super Lug

ibs

ups

Wet Concrete

Vel oci ty , mph Figure 1. Velocity iensitivi ty of peak Fx/FZ values at rated lodd. A Firestone Transport 1 0 General GTX 0 Goodyear Super Hi Miler Firestone Transport 200 0 Goodyear Custom Cross Rib Uniroyal Fleebnaster Super Lug

2 6 5 5 Velocity, mph gure 2. Velocity sensitivity of slide value of Fx/FZ at rated loatl. -33 - A Firestone Transport 1 0 General GTX 0 Goodyear Super Hi Mi ler A Firestone Transport 200 0 Goodyear Custom Cross Rib 1 Uniroyal Fl-eetrnaster Super Lug

Wet Concrete

Norm. Load FZ/FZFated

Figure 3. Load sensitivity of peak values of F,/FZ at 55 ntph. A Firestone Transport 1 0 General GTX 0 Goodyear Super Hi Miler A Firestone Transport 200 @ . Goodyear Custom Cross Rib B Uniroyal Fleetmaster Super Lug

Figure 4. Load sensitivity of slide values of Fx/F, at 55 mph. b-A b-A Firestone Transport 200 6- Goodyear Custom Cross Rib fl a. Uniroyal Fleetmaster Super Lug &-----4 Fi res tone Transport 1 0...... Q General GTX &--I] Goodyear Super Hi Mil er

Wet Concrete

5 10 15 2 0 Slip Angle, (n~g)

Figure 5. Lateral traction results, 40 mph, 0.5 x rated load. 3 Firestone Transport 200 -9 Goodyear Custom Cross Ri b m-m Uni royal Fl eetmaster Super Lug &,,,,,a Firestone Transport 1 0...... O General GTX Po--0 Goodyear Super Hi Mi ler

55 mph, 1 x rated load

Wet Concrete

Slip Angle, it (Deg) Figure 6. Lateral traction resuits, 55 mph, 1.0 x rated load. -Radials ---Bias Ply

F, (1bs) Figure 3.17. The load sensitivity of Fx/Fz values measured at 4% slip for heavy tires of radial and b~as-ply construction (tires are identified by code numbers previously listed in Table 3-1). 1.9 9

.9 a-

.8 =.

/ . .7 ==-- . aJ - 0 .F F Y, u Ca Y .6-- crr aJ CT

N LL \ *. X '5 k,

.4..'

.3 *=

, - 1 . . 1 I 0.5 1 .O 1'. 5 Normal ized Load z4/FzR Figure 3.18. "Peak and slide" values of Fx/Fz vs. load for individual bus tires--superimposed within the envelope of data taken on eight truck and bus tires at 20 m~h(for code identifications, see Table 3-1 ) . 51 Peak

lide

Normal i zed Load F. IFzR Figure 3.19. "Peak and slide" values of Fx/Fz vs. load for individual bus tires--superimposed within the envelope of data taken on eight truck and bus tires at 40 mph (for code identifications, see Table 3-1). i 1 0.5 Normal ized Load FdFZR

Itpeak and slide" values of FF/F2 VS- laad for individualtaken Figure 3.20. bus tira4yperi~p~~ed within the en'Je1oPe on eight truck and bus tires at 55 mph (for code identi ficati ons , see Table 3-1 b 53 Peak

Normalized Load FZ/FZR Figure 3.21. "Peak and slide" values of Fx/FZ vs. load for individual truck tires-superimposed within the en lope of dat taken on eight truck and bus tires at 20 mph !?or code nun?i er ;A~n+iC4r>+innc can Tabla '?-I \ 1.Or

$9-

.8--

Peak

.7-- a u .F Cvr u aC la .6a- Q, Q

N LL \ X .5--

- H-6 .4 -- --- H-1 . H-4 . . ..-H-8 .3 - H-5 , .

I 1 . 8 0.5 1.O 1.5 Normal ized Load Fz/FZR

Figure 3.22. "Peak and slide" values of Fx/rz vs. load for individual truck tires--superimposed within the envelope of data taken on eight truck and bus tires at 40 mph (for code number identifications, see Table 3-1). 55 Peak Peak

0.5 1 .O Normal i zed Load FZ/FZR

Figure 3.23. "Peak and slide" val~~esof Fx/Fz vs. load for individual truck tires-superimposed within the envelope of data taken on eight truck and bus tires at 53 mpn (for code number identifications, see Table 3-1). Envelope of all -

- H-12 7 9 ---- H-20 - H-8

..W."...U H-4

.. 7

I I I 1 10.0 Alpha (deg15.9 Figure 3.24. Lateral force measurements of heavy truck and bus tires at 20 mph and 0.5 x rated load. Envelope of all 8 tires

Alpha (deg)

Figu re 3.25. Lateral force measurements of heavy truck and bus tires at 20 mph, 1.5 x rated 1oad. J

.I - H-12 ---- H-20 -H-8

I -...-- H-4 . -Envel ope . .

, I I I I 10 15 Alpha (degs)

Figure 3.27. Envelope and specific examples of (Fy/Fz vs. a) measurements taken for 8 heavy truck and bus tires at 1.0 FZR and 20 mph. - Envelope

Figure 3.28. Envelope and specific examples of (Fy/F, vs. 3) measurements taken for 8 heavy truck and bus tires at 1.0 FZR and 40 mph. - Envel ope

Figure 3.29. Envelope and specific examples of (Fy/F, vs. a measurements taken for 8 heavy truck and bus ti res at 1 .0 FzR and 55 mph. Figure 3.34. Lateral force measurements of 1 ight truck tires at rated load, 20 mph. Figure 3.35. Lateral force measurements of light truck tires at rated load, 40 mph. 5 10 15 20 2 5 Alpha (degs)

Figure 3.36. Lateral force measurements of 1 ight truck tires at rated load, 55 mph. Figure 3.37. Example velocity sensitivity in the lateral traction performance of a Michelin 1 ight truck tire. 2 4 6 8 10 12 14 16 18 Slip Angle, a (degsj

. Figure 1.9. F versus a behavior of pickup truck tires at 2050 lbs. load. Y Overall, the van results indicate that the installation of four tires of the same type and at the same inflation pressure yields a reasonable directional behavior over the entire performance range regardless of the specific shear force behavior of the various types examined. In contrast, any fore/aft bias in ti re distribution which places the lower 1 ateral traction capabil i ty in the rear will result in the classical reduction in directional stabi 1 i ty. Particularly significant is the calculation of reduced yaw stabi 1 ity for the case of the OE ti re installed with its recommended inflation pressure bias. Insofar as 1 ight truck tires may or may not indicate the classical polarity of slope in their lateral traction sensitivity to inflation pressure, it would appear that recomnendations of a biased distri butioa of inflation pressure are open to question.

4.2.2 Simulation Results I1 lustratinq Vehicle Response Sensitivity to Tire Selections - Pickup Truck. Design parameters measured on the pickup truck test vehicle were applied in a sequence of simulations examining the i nfl uence of "pickup truck tires" on the yaw behavior of the subject vehicle. In these calculations the selected tires covered F /F versus a charac- YZ teristics as shown in Figure 4.9. As was shown in the case of the tires selected for the van simulations, the range of properties spans l.inear range variations as well as variations in the high slip behavior. Note, also, that the traction properties employed in these simulations represent actual tires rather than artificial ly-generated descriptions. Three tire configurations were examined with the vehicle in its unloaded condition. As shown in Figure 4.10, calculations of response to trapezoidal steer at 30 mph illustrate virtually zero sensitivity to the differing tires installed uniformly at all four wheel positions. Note that a1 though the sideslip response of the Eo data indicates a large departure from the other configurations, the expanded B scale tends to exaggerate an otherwise insignificant distinction.

109 ...... Co-CORNERING STIFFNESS (Ibs./degree) TABLE 3.1. FLAT-BED TEST TIRES Tire No, Manufacturer -Mode 1 -Size Heavy Truck Ti re3 H- 1 Unl royal Triple Tead 10 x 20F H-2 Uni royal Trfple Tread 10 x 20G C3 Unl myr 1 Triple Tread 11 x 22.5F ti-4 B.F. .Goodrfch .Milesaver Radial 10 R 20 G Steel H.D.R. H- 5 B.F. Goodrich Milesaver Radial 10 R 20 G Steel H.D.B. H-6 Goodyea r Unisteel R-1 10 R 20 G H-7 Goodyear Unisteel L-1 10 R 20 G H-8 Firestone Power Drive 10 x 20F H-9 Unf royal Unimas ter Rib 15 x 22.5H H-10 Hichel in Radial 10 R 20 G H-11 Uni royal Fleetmas ter 10 x 20F .-Superlug Heavy Bus Tins H-12 Ff res tone Hiway Hileage H-13 8. F . Goodri ch Intercity Mileage H-14 B. F. Goodrich Intercity Mi1 eage H-15 Unimyal Intercity H-16 Uni royal HaxRoute I H-17 Goodyear Custom Cruiser H-18 USchelin Radial XZA H-19 Michel in Radial XZA H-20 Michel in Radial XZA Lfght Truck Tires L-1 Fires tone Trans port 500 8.00 x 16.50 1-2 Goodyear Custom Hifliler 8.75 x 16.5E L- 3 Goodyea r Rib' HiHi ler 8.00 x 16.50 L-4 Fi res tone Transport 110 7.50 x 16.5C 1-5 Goodyear Super Single HiMiler 10.00 x 16.5E L-6 Ff res tone ; Town & country Truck 8.00 x 16.5D L- 7 Goodyea r Custom Flexsteel 8.00 R 16.5E L-8 Goodrich Milesaver Radial 8.00 R 16.5D 1-9 Goodyear Glas Guard XG 8.00 x 16-50 1-1 0 Goodyear Glas Guard XG 8.75 x 16.5E L-11 FI restone Town h Country Truck 8.75 x 16.5E 1-12 Good year Custom Flexs tee1 e.75 R 16.5E L-13 Michel In RadSal XCA 8.00 R 16.5E Lo14 Wards Steel Belted . 9.50 x 16.50 Super Wide L-15 Michelin Radlrl XCA 8.75 R 16.50

A L-16 General Jumbo Power Jet 8.00 x 16.50 L-17 General Jumbo Power Jet 8.75 x 16.5E L-18 Goodyca r Glas Guard 8.00 x 16.50 L-19 ~ood~ebr Glas Guard , 8.75 x 16.5E L-20 Goodyear Rlb YiHller 8.75 x 16.5E *. Vertical Load, F,, 1 bs.

Figure 4.19. Load sensitivity of the cornering stiffness parwtcr for the- thrh tires employed in intercity bus simulations. vehicle behavior resulting from the various tire installations were found to be so small as to be contained within the narrow envelopes indicated. The 1 ow velocity data, of course, i 11 ustrates the reduced yaw velocity gain and is expressed in this unnormalized fashion to give good data separation. As indicated, the loaded vehicle data falls below the empty vehicle responses in each case. Three tire selections, whose Ca/FZ curves are shown in Figure 4.19, are represented in these calculations; the bias-ply , tube-type base1 ine tire (Firestone Comnercial Mileage 12.5 x 22.5), a tube-type radial (Michel in XZA 11R20/H), and a tubeless radial (Michelin XzA llR22.5/H). Since tire construction mixes are scwpulously avoided in the operation of intercity bus fleets, the question of a fore/aft mix in carcass construction types was not addressed. Further, since the intercity coach is not, characteristically operated with 1ug-type tires on driving axles (in contrast to the line-haul tractor), the forelaft mix of tread types is, 1i kewise, a moot issue. A1 though the trapezoi dal .steer response data were selected here to illustrate the positive loading effect and'negl igible tire effects, detailed results illustrating other less discriminating maneuvers are presented in Appendix F.

4,. 2.6 Simul ation Results Specifically Addressi ng Heavy Truck Yaw Divergencies. A limited series of computations were performed using HSRI's digital simulation [4] to examine the generality of the divergent yaw response which was observed during full-scale testing of a heavy truck. The findings presented in this section serve to address the sensitivity of heavy truck spinout to various vehicle configuration parameters, thereby expanding upon the test results and computations presented in Appendix G (which directly explained the spinout/rol~loverincident occurring in this study). 900, ,

800 -

700 -

600 -

500 -

400, Firestone Transteel A Firestone Transteel Trac

0 Goodyear Unisteel R-1 300 - Goodyear Unisteel L-1

0 MichelinXZA . 200 - ID Michelin XZZ

100-

8,'

2 1 I I I I I -1 1000 2000 3000 4000 5000 6000 7000 ,. ,. Vertical Load, lbs

Figure 3 A Fi restone Trans teel A Fi restone Trans teel Traction

Q Goodyear Unisteel R-1 Goodyear Unisteel I-1 0 Michelin XZA 1.0- Michel i n XZZ

.9 - * Envelope of Peak Values

.8-

.7 -

a .6- u *r F v, u .5- Y Q QJ CT Envelope of Sl ide Values

N *4- LL \ X LL .3- Dry Concrete, Rated Load

.2-

J .I- .'

v f t 2b 46 Q 5 Velocity, mph Figure 4 r * A Fi restone Trans teel p Fi restone Trans teel Traction 0 Goodyear Unisteel R-1 O Goodyear Unisteel L-1 0 Michel in XZA Michel in XZZ 6

Envel ope of Peak Val ues /

Envelope of Sl ide Values

Dry Concrete, 20 mph

Fz'Fz~ated A Firestone Trans teel

Firestone Trans teel Traction

0 Goodyear Uni steel R-1 .o - Goodyear Unisteel L-1 0 Michelin XZA

.9- a Michelin XZZ

.8 - Peak Values

,7-

.6-

.5 -

.4 -

.3- L Envelope of Slide Values ..

.2-

1 - Wet Concrete, ~atedLoad

I do 4 0 ((. B Velocity , mph Figure 6

t 17 t + Firestone Trans tee1

A Fi restone Transteel Traction

0 Goodyear ~nisteelR-1

9 Goodyear Unisteel L-1

0 Michel in XZA

Michelin XZZ

Val ues

L~nvelopeof Slide Values

Wet Concrete, 20 mph .- .

Fz'Fz~ated

Figure 7

18 it should be noted, by the substantial degree of "mixing" which occur; among rib and lug data-quite in contrast with data taken on the similarly-limited sample of bias tires [2] which showed virtually no mixing and a 23%spread in average (Fx/FZ) peak values on wet concrete. Regarding "slide" traction values, the data taken on wet and dry concrete display virtually no significant rib/lug distinctions in the case of the radial truck tire. This observation again contrasts radials with bias-ply tires, the latter of which showed an average 16% lower slide traction performance of lug tires on wet concrete. In summary of longitudinal traction measurements, radial -ply truck tires, as represented in this sample, are not seen to be significantly discriminated,.according to tread type, by the gathered peak and slide traction values. As a note regarding the statistical qua1 i ty of the longitudinal traction measurements, the

' data obtained in the three repeat runs for each tire and surface are shown in Table 2. The tabulated data show that relatively good repeatabi 1 i ty was obtained, with a typical standard deviation of approximatefy ,012 for either peak or sl ide traction coefficients on both surfaces.

3.4 Mobile Traction Results - Lateral Tests were conducted on the 1ateral traction dynamometer to permit examination of the friction-1 imi ted lateral force behavior of the six-tire sample. Data resulting from these tests were reduced to the plotted format of Figures 8 through 11. These data indicate the basic sensitivity of the F /F versus a relationship YZ to velocity and vertical load under the two subject surface conditions. As with longitudinal traction measurements, the tire exhibits a steeply rising (elastic) behavior followed by a friction-determi ned saturation. In the case of lateral traction, the angular slip range of interest is 1 imi ted to about a = 20°, thereby eliminating any need

--- A Firestone Transteel --- 0 Goodyear Unisteel R-1 --- a Michelin XZA Fi restone Trans tee1 Traction -, -, A -t) Goodyear Unisteel L-1

, Michelin XZZ

Sf ip Angle, a (deg)

; 3 Figure 8 - ---A Firestone Transteel ---0 Goodyear Unisteel R-1 --- 0 Michel in XZA -A Firestone r ran steel Traction - Goodyear Unisteel L-1 -Fg Michelin XZZ

55 mph, Rated Load Dry Concrete

I I I 5 15 20 - $1ip Angle, a (deg) f: , Figure 9 ---A Fires tone Trans tee1 * ---0 Goodyear Unisteel R-1

---a Hichelin XZA -A Firestone Trans tee1 Traction -0 Goodyear Unisteel L-1 -a Michel in XZZ

------24 -0

20 mph, 0.5 x Rated Load • Wet Concrete

Slip Angle, a (deg)

Figure 10 ---A Fi restone Transteel ---0 Goodyear Unisteel R-1 - - Mi chel in XZA

-A Fi restone Transteel Traction

,,Goodyear Unisteel L-1 -a Michel in XZZ -

55 mph, Rated Load Wet Concrete

.' .' I 1 I 1 5 10 15 2 0 Slip Angle, a (deg) Figure 11

2 4 0) 10,00~20/~tins (2rnanufactuns)

I I I I I I I 10 20 30 40 50 60 VERTICAL LOAD, & VELOCITY, KM/H

1. 3: Lord semitivity in the peak and slide traction of a six-tire umpla on Fio 5: The differing influence of pavement surface on the velocity dry asphalt All tarts run at 64 kmlh. sensitivities of two tires.

1 I I I I 1 5 10 15 20 25 SLIP ANGLE, DEGREES

Fig. 6: fypial lord mitivitia in the iidm fom rapomof a sample of 10.00 x 20 tins tmtd at 32 km/h on e dw conate surface.

4: Velocity sensitiviw of tha peak md slide Wonvdua for a rix- tire sample on dry rrphdt All tim operated at their rapective 1 81 RA ratd lod. VERTICAL LOAD, Ib

Figure 3. Envelopes of the cornering stiffness parameter measured over a range of vertical loads. ? r ENVELOPE OF PEAK VALUES

.8 - - W .7 n mA cn .6 - n z 4 - 1L .5 a W ENVELOPE OF SLIDE VALUES e .4 - LLN \x GOODYEAR CUSTOM CROSS RIB UNIROYAL FLEET MASTER SUPER LUG LL .3 - A FIRESTONE TRANSPORT 200 A GOODYEAR SUPER HI MlLER 0 GENERAL GTX 0 FIRESTONE TRANSPORT 1

b t DRY CONCRETE, RATED LOAD

SPEED, mph

Figure 12. Peak and slide values versus speed for bias-ply tires at rated load on dry concrete. Q GOODYEAR CUSTOM CROSS RIB UNIROYAL FLEET MASTER SUPER LUG A FIRESTONE TRANSPORT 200 A GOODYEAR SUPER HI MlLER 0 GENERAL GTX 0 FIRESTOHE TRANSPORT 1

i b .9 ENVELOPE OF PEAK VALUES

ENVELOPE OF SLIDE VALUES

WET CONCRETE, RATED LOAD

SPEED, mph Figure 14. Peak and slide values versus speed for bias-ply tires at rated load on wet concrete. I

Peak

Slide

Goodyear Custom Cross Rib Uniroyal Fleet Master Super Lug

A Firestone Transport 200

a Goodyear Super Hi Miler t Genersl GTX

Firestone Transport 1

Fz/F 'rated

Figure 16. Peak and slide values versus load for bias-ply tires at 20 mph on dry concrete. 3 1 ENVELOPE OF PEAK VALUES

ENVELOPE OF SLIDE VALUES

t GOODYEAR CUSTOM CROSS RIB ID UNIROYAL FLEET MASTER SUPER LUG A FIRESTONE TRANSPORT 200 A GOODYEAR SUPER HI MlLER 0 GENERAL GTX U FIRESTONE TRANSPORT 1 .

WET CONCRETE, 20 mph

FzIFZ RATED

Figure 18. Peak and slide values versus load for bias-ply tires at 20 rnph on wet concrete. I I I $

- p. --- -.I ------7 BIAS RIBS I

..-. -

- -

DRY CONCRETE RATED LOAD I I I 40 SPEED, rnph

Figure 20. Envelopes of peak 1ongi tudi nal traction val ues obtained on dry concrete. -

WET CO I RATED LOAD I

FIgure 21 . Envelopes of peak longitudinal traction val ues obtained on wet concrete. I I I

- -

DRY CONCRETE - RATED LOAD -

i. I I I

SPEED, mph

Figure 22. Envelopes of slide values obtained on dry concrete. WET CONCRETE RATED LOAD

SPEED, mph

Figure 23. Envelopes of slide values obtained on a wet concrete surface, I / /// nav rn~rac~e un I uvrlwn.rc I c RATED LOAD, 55 mph

SLIP ANGLE, a

Figure 24. Envelopes of lateral traction performance on dry concrete. WET CONCRETE RATED LOAD, 55 mph

SLIP ANGLE, a

Figure 25. Envelopes of lateral traction performance on wet concrete. L -,,* -,,* Figure I. Ca vs Fz for Seven Tires '

1 -X)O - 0 -Mom

-4w- 4000 F, -1bs

' Two - Axh Hrovy Trutf - EW a 12,41e Ibr GW 29,127 Iba -roo. 10.0 x 20/F Tires (, (Dual tlnr m -P 9 g -300- 0 78-14 @ 24 pw " J

2m Fz mlbs Figure 4. G vs F, for Two-hle Bus and Heavy Truck

-250

0 Y 1 0 .65r Rot@d Rot& Lwd Load 0 6W 8927 Ibr Tin Sire: 8.0 x lLI/D 0 I I -17s. m n lnfkhon Pressure, psi Figure 5. The Effects of Inflation Pnnsura on Comering Stiffness: Van and Pickup Truck Two Light Puck Tires * 2. TEST TIRES

The tire sample was chosen to be representative of the entir( truck tire population, that is, representative in constructic brand and popularity. The number of tires of each brand seli for the test sample was based on the market penetration of tl sales of that brand, and the relative number of tires of the three major types (bias ply, ribbed tread; bias ply, lug tre; and radial ply, ribbed tread) was based on the relative popu: rity of the types. Table 1 lists the test tires and identifl their type.

All of the tires were of the 10.00 x 20 size and they were mounted on the proper rim recommended by the Tire 6 Rim Assoc ation. They were inflated to the maximum pressure (85 psi for bias ply tires and 90 psi for radial ply tires) and loade to a nominal 4,620 lbs.

Each tire was warmed-up by traveling about six miles at SO miles per hour immediately before being tested. Each tire was also broken-in by six brake applications of one second Ic up duration during the warm-up. The whole group of tires were tested in braking and then retested later in cornering as a group.

3. SURFACES

Two pavements very much like the Uniform Tire Quality Grading traction pads at San Angelo, Texas were used. The surfaces were located at the Transportation Research Center of Ohio. One surface was a hot mixed bituminous asphalt pavement with a nominal ASTM E274-70 skid number of 60. The other surface was a polished Portland cement concrete pavement with a nornin 4STN E274-70 skid number of 35.

Fig. 26 for Truck Comparison of Locked Wheel Braking Force Coefficient (pXI) Tire and Car Tire Populations on Concrete 0 al-a I1

N UO k -4 . Oc, MLa .4 4 M3 ra ra*4 0 a k a, m k .I+ 4 b a, a, k C cd 3 u Fig. 30

Comparison of Peak Braking Force Coefficient (pXp) for Truck Tire and Car Tire Populations on Asphalt

TABLE 2 -9 1 - i TRGCK TI2E TRACTION FORCE COEFFICIENTS ON CONCRETE CORRECTED FOR SURFACE WEAR

TIRE TIRE ' 40 mph 55 mph 40 mph 55 mph 40 mphp - 55 mph TYPE NO. avg s avg s avg s avg s avg s avg s

4B .211 5A .264 5B .247 8A .222 B 88 .232 I 1OA .266 A 108 .266 S 12A .201 12B .218 R 16A .245 I 16B .238 B 18A .250

B 9A .226 I 9B .233 A 1l.A .224 S 11B .214 13A .I76 L 13B ,167 U 17A .220 G 17B .245

1 A 7A .211 I i D 7B .212 I 14A .220 R 14B .217 I 15A .243 -B 15B .224 RE 26A ,184 CAP 26B .I71 TABLE 3 cg ?IRE TXCTIGN FORCE COEFFICIENTS ON ASPHALT CORRECTED FOR SURFACE PIEAR

%S ;TI3E . Lix~ LiyD 40 mph 55 mph 40 ntph mph E YO. . 55 40 mph 55 m?h avu 1s avgls awls avgls avgls avgls~~'

TABLE 5. CORRELATION BETWEEN TRACTION PROPERTIES

ASPHALT CONCRETE COblPARI SON 40 mph 55 mph 40 mph 55 mph

Fixs vs. p *P .563 ,400 .876 .720

1 VS .FI +xs YP . 20 . 05 .oos .05:

P vs.p YP X P -. 23 . 06 ,405 .285 r TABLE 6. STANDARD DEVIATION BETWEEN PAIRS OF TIRES OF THE SAME BRAND, MODEL AND SIZE, POOLED OVER VARIOUS CATEGORIES

# ASPHALT TIRE TYPE DEGREE^ OF 40 mph 55 mph - P P " " DOM Pxs xP YP pxs XP YP J Bias/Rib 11 .028 .022 .022 .016 .040 .024 Bias/Lug 8 .027 ,027 .021 ,011 .011 .024 Radial/Rib 4 .012 .024 .027 .009 ,031 .016 L All 23 .026 .024 ,023 .013 .031 ,023 I CONCRETE

40 mph 55 mph P U Px s " XP YP "xs "XP YP

Bias/Rib 11 .010 .010 ,011 ,033 .019 ,014

Bias/Lug 8 .010 ,014 ;007 .009 ,019 .016 Radial/Rib 3 $007 .009 .012 ,008 .006 ,023

All 23 ,010 .012 .010 .023 ,018 .016 overall overall ove all P C XP YP All 1 92 .019 .022 .019 m , IL 8666 U meee mr-rr z rrr. C .)888B B888 .b a a.mmmm Z ammmm W W 0

om99 ao-o 6 N'S Q mN4m teen

a-h 0.. BNO r.VQ

Chl --r -40 6-N rn 8 8

CQOI mom- -9NInP Il*-cU= 8 8

TIRF 1 Vertical Load, lb I Tire Speed Slip No. Angle 1165 2330 3495 No. Remarks mph Run I 1 55 A - x -

4 2 0 0 x x x j828 ! I -1 40 A - i 0 r iginal - I1 5 40 0 x x x HSRI Schedule 20 A - x 30 6 ' 55 0. x x x "130 JI

Table C-2. TIRF TEST SCHZDULE - BRAKING /CORNERISG

Longitudinal Slip Fro= 0 to - 1

Firestone 8,OO-16.5 D, Rim 6 in Inflation Pressure 80 psi TIRF DATA

GRAPHICAL PRESENTAT ION

RUN: 2- 1-22 1: F 't (tE5i RUN: 3- 1-32

1: F U (LES'i RUN: 5- 1-32

2330 lb 20 nph SLIP kNGLE !UEG i SLIP Gl4GL.E CEG 2

SLIP ANGLE !. IjEG i

TIME ELkPSED (5EC > 1 : tKiFM. T RACTIl.JE FORCE RUN 29- 1-32

TIME ELRFSEO C SEC> 1 : tUPH. TRUCT IVE FOPCE RUN 38- 1-32

TIME ELAPSED !SEC > 1 : LATEPfiL FOECE !LBSi RUH 31- 1-32 1 : UTEPfiL FORCE ( LES i RM 32- 1-32

SLIP ANGLE (LEG) 1 : UiTEPFiL FOKE ( LBS > RUN 33- 1-32

SLIP WCLE (DZ) 1 : LATERAL FORCE ( L6S j RUN 34- 1-32 1 : UTEPfiL FORCE (LES > RUN 35- 1-32 1 : LATERAL FORCE (LES i RUN 36- 1-32

SLIP AHGLE ( i3EG > Table C-6

LISTED DATA SYhlBOLS

DIhIESS IOSS SMlBOLS PARAMETERS ENGLISH S. I.

FORCES AiYD MO:*lENTS FX LOSGITUDISALFORCE* rb N FY LATERAL FORCE* 1b N SFY NEGATIVE LATERAL FORCE (- FY) 1b N FZ NONULFORCE* lb N AVL AHALOG VERTIC~LOAD lb N TF (DEF. 1) lb N FR ROLLIRG RESIST.Q~CE* (DEF. 2) I b N MX OVERTURNISG I.!ONE~T* ft-lb s-1: MY ROLLISGRESIST;LYCE MOIIENT* ft-lb N-in I MZ ALIGNING TORQUE* ft-lb N- R 1fI' TPAVS:4ISS ION GUTPUT TORQUE (DZF . 3) ft-lb N-;n

T WEEL TORQUE* ft-lb tvh-n BFT BEARING FRICTION TORQUE (DEF. 4) ft- lb 9-m PRESSURE P INFLATIOS PRESSURE psi bsr SPEEDS RS ROAD SPEED . mph km/h N WHEEL ROTtIT!ONS PER MIN'JTE *Fm rpr. 1 R PMEEL ROTATIOSS PER MILE (CIR km) rev/mi rev/kz 1 (DEF. 5)

LONGITUDINAL SLIP SR (DEF. 6) - - LS (DEF. 7) - - ANGLES sA SLIP ANGLE* d ~g deg * I IA IKCLIXATIONr\r;~~.~ dcg deg-- 1 Table C-6 LIST DATA SYIIBOLS (Cont d)

DIMENSIONS I SfililOLS PARAMETERS ENGLISi-1 S.I. i TIRE RADII * RH RADIUS- L0:ZDED in cm * RE RADIUS-EFFECTIVE (DEF. 8) in cm -TICE TE TIME ELAPSED scc sec TIRE COEFFICIENTS NFX FX/FZ - - NFY M/FZ - - h?ff W/FZ - - NMZ MZ/ FZ -. - F GM f-FU?;CTION - - G Gbl g-FUKCTiON - - H Gbf h-FCTSCTION - - A GM ALIGNING TORqUE FUSCTION ft cm

t DEFINED ACCORDISC TO SAE J67Cc Table C-7

SYblBOL DEF ISITIO>;S

r NO. DEFINITION

BFT 1 TF = FX - - x 12 (FOX PROGRU1 CIECKOUT) R I3 2 FR = -FX FOR FXEE-ROLLING TIRE (T=O) 3 HI = T - BFT; (FOR PROGW1 CHECKOUT)

4 BFT IS NEGATIVE N 5 R = 60 .- RS N xRH' 1; k* = 168.07 FOR ESGLISH SYSTE\I 6 SR = - 265.26 FOR S. I. SYSTE:&I k*x RS

7 IS =JRS rJ - 1 FREE ROLLIKG *RS 8 RE=k-N

8, I.. 1 ,.

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- - NFY TE

FIRESTONE TRflNSPORT 500 VIDE OVfiL 8.00X16.5/0 VEL 40 MPH F I AESTONE TRflNSPORT 500 Y I DE OVflL 8.00X 16.5/0 FZ * 2865 LB ua8 1 rr HSRI HOB ILE DYNflHOflETER , cu 09- JflN -76 8 cl) xe u==' d, 3

RUN = l - 2 RUN = -RUN 3 - = RUN = 4 -RUN = 5

FtLPHfl [DEGREES I

FIRESTONE TRflNSPORT 500 WIDE OVRL 8.00X16.510 FZ = 2844 LB VEL = 40 MPH , HSR I MOB ILE OY NflMOMETER 21 -0CT-75

-FZ = 2459 LB -FZ = 2773 LB -FZ = 3146 La I I I I I r 5.00 10.00 15.00 flLPHfl CDEGREESI

F IRESTONE TRflNSPORT 500 8.00X 16.5/D VEL = 40 MPH As?HALT cl HSRI MOBILE DYNftHOflETER 17-OCT-75

6 CD,.

e (D,

N L >\ Le53 5,

8 CY, m

-VEL = 21 PtPH VEL = 40 MPH 8 - 6 . I I I I 5.00 10.00 15.00 20.00 25.00 flLPHR [DEGREES]

F IRESTONE TRRNSPORT 500 8.00X 16.5/D FZ = 2771 LB ASPHALT F IRESTONE TRRNSPORT 500 8.00X 16.5/D FZ = 2787 LB VEL = 41 MPH AsPt-1 cr F I AESTONE TOYN b COUNTRY TRUCK 8.00X 16.5/0 VR = 40 MPH HSRI HOB ILE DYNflHOHETER 09- JAN-76

-VEL flPH -VEL NPH -VEL flPH

5. 00 10.00 15. OQ 20.00 4 RLPHf3 C DEGREES I

FIRESTONE TOYN b COUNTRY TRUCK 8.00X16.5/0 FZ = 2804 LB e' rr

CY 8 d xs us e' 3

9 8 3 CI)

n A-mz "R > L

s8 e' H -RUN 1 RUN = 2 -RUN 3 -RUN = 4 a8 e' RLPHfl CDEGREESI

F IRESTONE TOWN b COUNTRY TRUCK 8.00X 16.5/D FZ : 280 1 LB VEL = 40 NPH 5.80 lQ.OO 15.00 2Q. Q0 25. QQ RLPHA CDEGREESI

GENERAL JUMBO POVER JET 8.00X 16.5/0 VEL = 41 MPH 0. 00 5.08 10.00 15.00 20.00 25.00 ALPHR C DEGREES I

GENERBL JURBO POWER JET 8.00X 16.5/D FZ = 2843 LB -RUN a 1 -RUN 2 -RUN 3 RUN a 4 -RUN = 5

I 0.00 5.00 10.00 15.00 20.00 2: ALPHA C DEGREES I

GENERRL JUMBO POWER JET 8.00X 16.5/D FZ 2832 LB VEL = 41 MPH u ancrc * . .. r N... N.C -w...m4 .e 0 8888 z r.... - .)O(fBB z at-wf-w U I A GOODYEflR CUSTOM FLEXSTEEL 8.00R 16.5/€ VEL = 40 MPH HSRI MOBILE DYNRflOMETER C 09- JRN-76

a,6 a

8 (0, a

N LL >-\ LL, 3'- a

8 CY-. -VEL = 21 PtPH -VEL = 41 MPH -VEL = 56 RPH 8 8 a 1 I I I 0.0$ 5.00 10.00 15.00 20.00 2: ALPHA [DEGREES I

GOODYEAR CUSTOM FLEXSTEEL 8.00R 16.51E FZ = 3025 LB 8 mm HSR I MOB ILE DYNAMOMETER , CY 09- JflN-76 8 v-4 xs -61 8, Y'

8 8 8, cr)

rn m: J -R > IL

8 8 8 4 -RUN = 1 -RUN = 2 -RUN - 3 -RUN = 4 8 RUN = 5 8 - 8 s'. 0d 5.00 10.00 20.00 ALPHR C DEGREES I

COOOYEflR CUSTOM FLEXSTEEL 8.00R 16.51E FZ = 3026 LB VEL = 41 MPH 5.00 18. QQ 15.08 28. QO 25. QO ALPHA C DEGREES 1

HICHELIN XCR 8.00R16.5/€ V€L = 41 HPH

5.00 10.00 15.00 20.00 25.00 RLPHfl CDEGREESI

HICHELIN XCfl 8.00R16.5/E FZ : 3084 LB VEL = 41 NPH This expectation is confirmed by Fig. 13 which compares the tire were half of the dual tire loads indicated on the abscissas carpet plots of lateral force versus slip angle and vertical load of Fig. 14. :'or dual tires with twice the measured lateral force from the The dual tire aligning moment as a function of slip angle single tire. The vertical loads in Fig. 13 are twice the test and vertical load was found to be very close to twice the loads on the single tire. single tire aligning moment measured at the same slip anples Figs. 14A-14B show the dependence of the traction stiffnesses and half of the loads on the dual assembly. A comparison of C, and C Y on vertical load. The vertical loads on the single the moment data for selected slip angles is given in Table b. CLOSURE

Table 4 - Mechanical Properties of Single and Dual It cannot be overemphasized that the tire data presented in Tire Assembly at 65 psi this paper have been obtained in a specific set of experiments on a single testing n~achne.From the hi&way data available Single* Dual**

Cs, Ib/unit slip 3 1,000 54,000 Ca, lbldeg 311.1 594.4 lb, deg 500 Cy, lbldeg 52.0 97 .I - 3-22.;/3 65 ?ji K,, Ib/in 1,279 2,423 400 - K,, lblin 2.690 5,756

Single *Single tire load is 2750 Ib (rated single tire load I00 - is 3140 Ib). **Dual tire load is 5500 Ib (rated load). iOS -

I I I 1 I Table 5 - Dependence of Single and Dual Tire Lateral Force 1330 4000 0530 900'2 1Cll00 I lb) on Inflation Pressure

Lateral Force, at 6 deg Slip Angle, Ib Pressure, psi Single* Dualx*

*Single tire load is 2750 Ib. **Dual tire load is 5500 Ib. Tire Loau 15 I Ci I I I I I

2000 50013 6250 3000 1350t I lh' Fig. 14 -Variation of dual and single tire mechanical properties with tire load. A-cornering stiffness versus tire load: Bcamber stiffness versus tire load

Table 6 -Comparison of Dual and Single Tire Aligning Moments* at 65 psi

Aligning Moment, ft-lb, at Indicated Slip Angle, deg 1 deg 4 deg 12 deg Dual Tire ------Load, Ib Dual Single Dual Single Dual Single

Fig. 13 -Comparison of lateral force versus slip angle and vertical load on dual assembly of 8-22.51D tires with twice lateral force obtained *The single tire moment is twice the measured value. from single 8-22.5/D tire operated at same pressure, slip angles, and half of vertical loads applied to dual assembly DUAL VERSUS SINGLE TIRE TRACTION differences to be expected in dual and single wheel application. .A special experiment was conducted to determine the rela- To eliminate the effect of inflation pressure, the single tire :?:;;:, ... , ...... tionship between the force and moment producing properties tests were run at the rated dual tire pressure, 65 psi. This .::.I:.. of tires used as singles with the same tires used as duals. A practice was followed because the influence of inflation pres- nylon 5-22.51D rib-type 11 tire (Fig. 6B) was selected for test. sure on the lateral force developed by single and dual tires is bemg the niaximum size that cou!d be mounted in a dual measurable, though slight (Table 5). configuration on the flat bed machine. To represent the dual Table 4 shows that the vertical spring rate, KZ,of the dual configuration. the tires were mounted on a precision dual rim tire assembly is sli$tly more than twice the single tire spring with 5.25 in bead spacing. The inflated sidewall spacing was rare. For identical tires. each carrying half of the vertical I in. For sin~jetire testing, the test tire was mounred on the same rim with 5.25 in bead spacing located midway between load. the spring rate should be exactly two times the single the previous duals (dashed outline in Fig. 12A). tire rate. The variation may be attributed to a slight differ- The bead spacing used in these tests is less than the 6.00 in ence in tire stiffnesses. desip rim width. Nc data are yet available on the influence A comparison of the C,, C,, and Cy values tabulated in of rim width, but it is believed that the mechanical properties Table 4 suggests that the traction force generated by dual .I-:~I .i~tr*:;~:Yorczs measured in this test are indicat~veof the tires should be nearly double that generated by a single tire.

Fig. 12A - Dual and single tire positioning on precision test rim

Fig. 12B - Dual tire assembly mounted in flat bed tire testing machine Tire: Highway Tread 8-22.5/D: Single Rim: 22.5x5.25

LATERAL FORCE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Lateral Force at Indicated Slip Angle (degs. ) Load Pressure ( lbs .) (psi) ------1 2 4 8 12 16 900 65 153 29'2 447 643 712, 748

ALIGNING TORQUE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Aligning Torque at Indicated Slip Angle (degs. ) Load Pressure (lbs.) (psi) ------1 2 4 8 12 16 900 65 13 22 25 10 3 1

CIRCUMFERENTIAL STIFFNESS vs SLIP ANGLE AND NORMAL LOAD Vertical Inflation Vertical Load Pressure s Spring Rate (~bs.) (psi) (~bs.) lbs. /in. ) 2750 65 31,000 2690 Tire: Yighwa:; Pead 8-22.5/3: Dual Fiim: 22.5x:.2'

UTE.%; ?ORCE vs SLIP ATr'GLE: AIVD VERTICAL LOAD Vertical Inflation Lateral Force at Indicated Slip Angle (degs . ) Load Pressure (lbs.) (psi) ------1 2 4 8 12 16 1800 6 5 294 543 911 1249 U94 1452

ALIGNING TORQUE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Aligning Torque at Indicated Slip Angle (degs. ) Load Pressure (lbs.) (psi) 65 65

CIRCUMFEiiENTIAL STIFFNESS vs SLIP ANGU AM) NORMAL LOAD Vertical Inflation Vertical Load F'ressure Cs Spring Rate (~bs.) (psi) (lbs. ) (~bs./in. ) 5500 6 5 54,000 1556

mum

Tire: Highay Tread 8.25-20/~ Rim: 2Cix'.OO

LATERAL "RCE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Lateral Force at Indicated Slip Angle (degs.) Load hessure (~bs.) (psi) ------1 2 4 8 12 16 1300 85 188 368 636 969 11.37 1.001

ALIGNING TORQUE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Aligning Torque at Indicated Slip Angle (degs . ) Load Pressure (lbs. ) (psi) ------1 2 4 8 12 16 1300 85 16 30 40 32 17 4

CIRCUMFERENTIAL STIFFNESS vs SLIP ANCU AND NOWLOAD Vertical Inf letion Vertical Load Pressure Cs Spring Rate (~bs.) (psi) (~bs.) (~bs./in. ) 1300 85 14,000 , GOODYERR SUPER HI-HILER WIDE TREAD 8.75X16.5/E VEL = 40 MPH GOODYERR SUPER HI -MILER VIDE TRERD 8.75X16.5/€ FZ = 2646 LB 8 1 mm HSR I MOB ICE OY NRMONETER CY 09- JAN-76 8 c( x- u? 8, 3

8 8 8, m rr

> IL

6 8. -RUN = 1 -RUN = 2 -RUN = 3 -RUfl = 4 -RUN = 5 5.00 10.00 15.00 20.00 25.00 ALPHA CDEGREESI

GOODYEBR SUPER HI -MI LER U ID€ TRERD 8.75X16.51E FZ = 2832 LB VEL = 40 MPH , HSR I MOB I LE DYNflNOHETER 21-OCT-75

C 5.00 10.00 15.00 20.00 C RLPHfl CDEGREESI

COODYEflR HI - MI LER W I DE TREflO 8.751 16.5/E VEL = 39 MPH A~PH~LT GOOOYEfiR HI-MILER WIDE TREfiD 8.75X16.5IE FZ = 3268 LB ASPH A CT 8 In rn HSRI MOBILE DINRNONETER CY 21 -0CT-75 8 .-( x- u? 8, 3

n mz J us-rJ > LL

8 6 9, d

-HUN = 'I I 5.00 10.00 15.00 20.00 2 5 ALPHA CDEGREESI

GOOOYEflR HI-MILER WIDE TRERD 8.75X16.5/E FZ = 3314 LB VEL = 40 MPH ASPHALT GOOOYEflR GLflS - GURRD XG 8.7% 16.5/E VEL =. 41 NPH HSRI PIOBI LE DYNAMOMETER 09- JAN-76

VEL * 21 NPH -VEL * 48 NPH -VEL = 56 HPH

8 5.00 10.00 15.~0 20. QO 4 RLPHR C DEGREES I e nin

Cu 8 H x- us =m

e 8 cn6 a38n J

2. L

8 m. 8 C1 RUN 1 -RUN 2 -RUN 3 -RUN = 4 8 RUN * 5 8 - e'

GOODYEAR GLRS- GUflRD XG 0.7% 16.5/€ FZ = 2945 LB VEL = 41 NPH TABLE 3.1. FIAT-BED TEST T IRES

Tire No. Manufacturer -Mode 1 -Sf ze Heavy Truck Tins H- l Uni royal Trlple Tread H- 2 Uni royal Triple Tread H- 3 Unfroyal Trlple Tread H-4 B.F. .Goodrich Milesaver Radial Steel H.D.R. H- 5 B.F. Goodrich Milesaver Radial Steel H.D.B. H-6 Goodyear Unisteel R-1 H-7 Goodyear Unisteel 1-1 H-8 Firestone Pcwer Drive H- 9 Uni royal Unimas ter Rib H-10 Hichel in Radi a1 ti-1 1 Uniroyal Fleetmas ter Superlug Heavy Bus Tires H-12 Firestone Hiway Mi leage H-13 B.F. Goodrich Intercity Mileage H-14 B.F. Goodrich Intercity Mi1 eage H-15 Uniroyal Intercity H-16 Uniroyal HaxRoute I H-17 Goodyear Custom Cruiser H-18 Hlchelin Radial XZA H-19 Hichel in Radial XZA H-20 Michel in Radial XZA Light Truck Tires I-1 Firestone Transport 500

Goodyear Rib' HiMi ler Fl nstone Transport 110 Goodyear Super Single HiMi ler Flres tone Town & cduntry Truck Goodyear Custa Flexsteel Goodrich Milesaver Radial Goodyear Glas Guard XG

Radial XCA Wards Steel Belted . Super Wide

General Jumbo Power Jet

L-18 Goodyca r Glas Guard 8.00 x 16.50 9- m Figure 3.34. Lateral force measurements of light truck tires at rated load, 20 mph. Figure 3.35. Lateral force measurements of light truck tires at rated load, 40 mph. 10 15 Alpha (degs)

Figure 3.36. Lateral force measurements of light truck tires at rated load, 55 mph.

*mu * . .* cue- 8.N 8 8

- b. m Y 2 8888 8668 Z r Ormoo C Orrmr 1 4UNBQ f N8Q * w 08SO- W 08- ? U 0-49 X PC94 a -wn o 4 N n 0 x

measured Increase in C, and by the carpet plot comparison is a result of increased tread compli~~lcc*.It would he of. given in Fig. 7. considerable interest to compare [lie peak braklnp traction of Fig. 7 represents the extreme in force variation found in this the rib-type and open tread tlres. Altl~ou.gh the force mea- study of ply ratlng and tlre size. More tests are needed to suring equipment employed in these tests was incapable of establish firmly the trends evident in Table 2. responding tu a longitudinal slip much above s = 0.04**, the higher initial slope (indicated by the measured CS)of the F, TREAD PATTERN INFLUENCE *This is to be expected in the open pattern which has ap- It is widely recognized that the tread pattern is a very im- proximately twice the void area of the closed rib-type pattern. portant factor in wet traction performance. However, it also **Far below that required for peak braking force generation. appears that pattern influence is noticeable in the data from low-speed dry-traction flat bed tests. Fig. 6 shows the three 10.00-20lFnylon tires, similar except for tread design, that were tested in this study. Listed beneath the tires are the five basic mechanical properties defined earlier. The values shown were measured at rated inflation pressure, 85 psi, and rated load. 5430 Ib. From an examination of the data, it appears that tread design has little influence on the tire spring rates K and K,. Y The cornering stiffness, Ca, was affected very little although the open tread did generate slightly higher lateral force at higher slip angles than the rib-type pattern (see comparison presented in Fig. 8). The camber stiffness, Cy, was substantially changed by the tread pattern. In Fig. 9, it is seen Fig. 7 - Comparison of lateral force versus slip angle and vertical load that the open tread generated considerably less lateral force on 10.00-20 tires with ply ratings F and G (or camber thrust) than the rib-type pattern. The marked decrease in iongitudinal stiffness, Cs (Fig. 6),

Table 1 -Tires Tested to Determine Influence of Ply Rating and Tire Size on Mechanical Ruperties

Tire Test Test Size and Rating Pressure, psi Load. Ib

Fig. 8 - Laterai force versus slip angle and vertical load on open and rib-type 11 tread patterns

Table 2 - Measured Mechanical Properties for Three Sets of Two Tires Which Differ Only in Ply Rating

9.00-20 10.00-20 1 1.00-22 Tire Ratine E F F '-G -F- G Unlroyol Fleetmcster 9-20/E Dry Asphalt, 60mpn 091

oV i0 iolo 5b do 70 gb !do , LONGITUDINAL SLIP, Percent Fig. 5 - Example of "p-slip" history measured on dry surface

break-in, the tire was operated at its rated load and at the Notable characteristics of the Fig. 5 example include a reference value of inflation pressure described above. force peak occurring in the vicinity of s = 20%, followed by a rather steep negative slope out to s = 85%, at which DISCUSSION OF PRELIMINARY point an abrupt inflection occurs, depressing the locked TRACTION MEASUREMENTS wheel value further. Over a sample of eight tires tested on The mobile dynamometer described earlier has been a dry bituminous asphalt surface (SN - 78) the ratio of r .ted under various conditions of test surface, veloc- peak-to-slide F,/F, ranged from 1.50 to 2.02 with the ity, tire load, and tire samples to produce analog mea- force inflection in the high slip regime being observed surements of the longitudinal traction of truck tires. over a majority of conditions. Comparing this general As indicated previously, the preliminary measurements curve shape with those commonly measured on dry sur- which are reported here involve longitudinal force data faces with passenger car tires, we observe that the truck which has been scaled usingsteady-state Fx and My re- tire's narrow, accentuated peaking, followed by a 30-5V/, cordings. Thus the interpretation of gbsolute values in the reduction in force capability at lockup contrasts mark- normalized longitudinal force measures is not encouraged, edly with the car tire's rather flat shape in the 20-100% since the torque scaling of Fx neglects that torque compo- slip range. nent which derives from the rearward deflection of the vertical load vector during generation of "braking" shear The typical p-slip curve shape which was measured forces. Although the data have been corrected to account with truck tires on a wet jennite-coated asphalt (SN = for thls influence, per estimates based upon static laboratory 20) is shown in Fig. 6. In this case, the on-board water measurements of truck tires, we suggest that the presented delivery system was employed to deposit a water film of data have greatest merit as indicators of relative sensitivities, 0.025 in nominal thickness ahead of the test tire at 20 While longitudinal force production has been found to be mph test velocity. (The film thickness dimension is de- sensitive to various operating conditions, the single property fined as the height of the rectangular cross section stream which most significantly distinguishes truck tires from auto- which is deposited on the test surface at the indicated mobile tires concerns the remarkable peak-to-slide ratios velocity-. .) which are exhibited on dry surfaces. shown in Figure 5, The broad peak on the Fig. 6 curve is a characteristic the typical dry asphalt performance is summarized in the which was observed over all specimens in the eight-tire form of a slip" history (a plot of normalized longitudinal sample. In most cases, the peak value of F,/F, is sus- force, Fx/FZversus the ratio of instantaneous tangential tire- tained to within & 0.02 over a band of longitudinal slip V Reo which is the excess of 40%. The peak-to-slide ratios on to-road relative velocities, s =- x 100%) v the wetcoated asphalt were seen to range from 1.53-2.02. Although the pronounced peak-to-slidedecrement is I. e V = vehicle velocity comparable to passenger car tire performance on such a E$= effective rolling radius of the test tire surface, the broad peak characteristic of the truck tire o = angular velocity of the test tirc sample is notable. I Unlroval Fleetmaster 12-20/G Wet Jenn~te, 20 mph I

LONGITUDINAL SLIP, Percent Fig. 6 Typical "1-slip" history measured on wet, jennite- mated surface

BASELINE DATA SUMMARY range over which the 15 x 22.5 tire could be tested, suf- ficient data was obtained to indicate significant differ- Shown in Fig. 7 is a summary of peak and slide values ences in normalized longitudinal force capability. Also of F,/F, for the tire sample on the dry asphalt surface. shown in Fig. 9 are peak and slide values taken over a The general load sensitivity of the subject sample is indi- somewhat narrower load range on asphalt, with the 10 x cated by the variation in performance over the three ex- 20 tire. While the peak values differ markedly in both

amined load levels, expressed as a fraction of the T&RA 0 8.25-~O/E recommended load for each tire. A two-point velocity 9-20/E sensitivity indicator is provided at each load level by the A 10-20/F 40 and 60 mph data. A 12-20/G In general, the data are rather closely grouped, al- 0 12-22.5/F though the sample of tires was by no means representa- 1 15-22.5/H tive of the range of constructions and rubber compounds Fz ost which are available. As can be deduced from the spread -* 1.0 Fz ratN between the peak and slide values, peak-to-slide ratios are Fz 1-t -- -1.5 higher at the lower velocity-since the peak F,/F, data FZrated show a significant decrement with velocity in the 40-60 mph range while slide values are essentially unchanged. Shown in Fig. 8 is a summary of peak and slide F,/F, as measured for an eight-tire sample on a wet jennite- I 0.7h coated asphalt. These data, all taken at 20 mph, are presented as a function of vertical load, normalized to the \a T&RA rating of each tire. All of the sample tires in- IA Values corporated a common highway rib tread design and thus 0.6 Slide we might have anticipated the fairly consistent wet sur- VOIUCS face performance indicated across the sample. Neverthe- less, the remarkable tight grouping does suggest that the T&RA load rating is a powerful normalizer. SENSITIVITY TO VERTICAL LOAD - Data taken over a wide range of vertical loads on dry concrete (SN = 75) are shown in Fig. 9. For comparison of two tires of widely differing load rating, a 10 x 20/F sample is represented together with data from a 15 x 22.5/H wide base single tire. Although the brake torque Fig. 7 - Summrn of F,/F, peak and slide data-dry asphalt, 40 and capability of the mobile dynamometer limited the load 60 mph

FZ = 7116;s VEL r 68.9 MULOCK = 0;s~ HUPEAK 0;66 RATIO 1.75 Tire: Highway Tread 9-~O/E Rim: 23x7.C: i4E.3AL FTj3'JE .is SLIP AiJGE AND VERTICAL LOAD

Vertical Inflation Lateral Force at Indicated Slip Angle (degs. \ Load Pressure (I~s.) (psi) ------1 2 l4 e 12 16 15 GO 80 216 388 632 911 1026 1.046

ALIGNING TORQUE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Aligning Torque at Indicated Slip Angle (degs.) Load Pressure (~bs.) (psi) ------1 2 4 8 12 16 U 00 80 19 29 32 19 8 0

CI2CUMFERENTIAL STIFFNESS vs SLIP ANGLE AND NORMAL LOAD Vertical Inflation Vertical Load Pressure Cs Spring Rate (~bs.) (psi) (~bs.) (~bs./in. ) 1300 80 14,000 4 160 80 41,000 3824 6500 8o 6, goo Tire: Higbay Tread 9-2Q/F Rim: 20~7.00

I LATERAL FORCE vs SLIP ANGLE AM) VERTICAL LOAD I Vertical Inflat ion Lateral Force at Indicated Slip Angle (degs.) Load Pressure (lbs.) (psi) 1 2 4 8 12 16 ------, 14CO 85 238 440 718 1001 2 1232

ALIGNING TORQE vs SLIP ANGLE AND VERTICAL LOAD Vertical Inflation Aligning Torque at Indicated Slip Angle Load Pressure (lbs.) (psi) ------1 2 4 8 12 16 1400 85 20 33 38 20 6 -3 2800 35 52 89 118 87 49 19 4250 85 84 148 213 187 118 74

CIRCUMFERENTIAL STIFFNESS vs SLIP ATiGLE AND NORMAL LOAD Vertical Inflation Vertical Load Pressure Cs Spring Rate (lbs. ) (psi) (lbs.) (lbs./in. ) 1400 85 16,000

monte n.mu ..a ...... lo 800.- -*nnry- B m-n B9r*89 * *r.YN 8#* ObCC om.. 9ac-e --OOOO ++089 dm- Alpha (degs)

Figure 3.34. Lateral force measurements of light truck tires at rated load, 20 mph. Alpha (degs)

Figure 3.35. Lateral force measurements of 1 ight truck tires at rated load, 40 mph. Figure 3.36. Lateral force measurements of light truck tires at rated load, 55 mph. 6000YEflR SUPER SINGLE 10.0031 6.5/D VEL = 41 HPH COODYEflR SUPER S I NGLE 10.00X 16.5/0 FZ = 2984 LB -RUN = 1 RUN = 2 I -RUN = 3 RUN * 4 -RUN 5

0. 0d 5.40 10.00 15.00 20.00 25.09 RLPHA C DEGREES I

GOODYEAR SUPER SINGLE 10.08X16.5/0 FZ : 2980 LB YEL = 41 NPH TABLE 3.1. FLAT-BED TEST TIRES

Tire No. Manufacturer Mode 1 -Size Heavy T~ck Tires

H- 1 Uniroyal Triple Tread H- 2 Unl wal Trlple Tread H- 3 Uniroyal Triple Tread H-4 B.F. .Goodrich Mllesaver Radial Steel H.D.R. H- 5 B.F. Goodri ch Mllesaver Radial Steel H.D.B. ti-6 Goodyear Unisteel R-1 H-7 Goodyear Unisteel L-1 H-8 Firestone Power Drive H- 9 Uni royal Unirnas ter Rib H-10 Hichel in Radial H-11 Uniroyal Fleetmas ter c Superlug Heavy Bus Tires H-I2 Firestone Hiway Mileage H-13 B.F. Goodrich Intercity Mileage H-14 B.F. Goodrich Intercity Mileage H-15 Uniroyal Intercity H-16 Unlroyal HaxRoute I H-17 Goodyear Custom Cruiser H-18 Mi chel in Radial XU H-19 Hichel ln Radial XZA H-20 Michelin Radial XZA Llght Truck Tires 1-1 F 1res tone Transport 500 L-2 Goodyear Custom HiMiler L-3 Goodyear Rib' HiHi ler 1-4 Ff restone Transport 110

Ft restone Town L Country Truck Goodyear Custom Flexs teel Goodrich Milesaver Radial Goodyea r Glas Guard XG Goodyear GlaS Guard XG Firestone Town 6 Country Truck Goodyea r Custom Flexs teel Michell n Radial XCA Wards Steel Be1 ted . Super Wide Hlchel in Radial XCA Genera 1 Jumbo Power Jet General Jumbo Power Jet Goodycar Glas Guard ~oodyear Glas Guard Goodyear Rib HiMfler \.