Wheel Alignment!

4WD Mechanix© Magazine…Issue #6, July 2010. For Fast Navigation, Use the Adobe Reader® “Bookmarks” Feature...There is a bookmark for each listed ‘Table of Contents’ item!

4WD Tech: ‘DIY’ Wheel Alignment!

4WD Mechanix© Magazine…Issue #6, July 2010. For Fast Navigation, Use the Adobe Reader® “Bookmarks” Feature...There is a bookmark for each listed ‘Table of Contents’ item!

Wheel alignment is a basic vehicle maintenance need. Suspension modifications, normal chassis and steering linkage wear, off-pavement trail pounding and the use of oversized tires can each affect front wheel alignment.

The popular, time-honored Jeep off-pavement trail runners have a beam (“solid”) live front axle. More civilized Jeep models with independent front suspension (IFS) include the KJ Liberty, 2005-up

Grand Cherokee and the Commander. Each of these Jeep vehicles has a hypoid, solid rear axle assembly. The less complicated beam front axle is not just strong and durable. It also has fewer maintenance Since most trail vehicles upgrade to expensive, requirements. Camber is set at the factory with the oversized traction tires, premature wear of tires is jig-welding of the beam. Caster is adjustable for the always a concern. Periodic tire rotation and proper slight sagging of aged springs or the settling of wheel alignment are basic safeguards to prevent spring or link arm bushings. For all Jeep vehicles, a abnormal tire wear. common alignment need is toe-set.

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Caution: Wheel alignment is never a substitute for alignment can handle any vehicle with a solid, replacing worn or damaged parts. A bent steering hypoid rear axle system. knuckle, tie-rod or axle beam is a candidate for replacement. Straightening trail-damaged steering linkage or a bent knuckle is not safe practice. Periodic Alignment Needs

Wheel alignment at the modern shop most often includes four-wheel “thrust” inspection and a check of the caster, camber and toe-set. Some shops can perform a true “four-wheel alignment,” but this is generally not necessary on the trail-oriented Jeep models unless an aftermarket lift kit has adjustable rear wheel link arms or there is suspicion of a bent rear axle or frame damage. To push the vehicle forward in a straight line, rear Thrust alignment does take rear axle shift, worn axle thrust must be perpendicular to the centerline springs, bad bushings or a bent frame into account. of the frame. When thrust is correct, a front wheel A shop that performs either four-wheel or thrust alignment assures precise steering and a normal steering wheel position.

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On turns, the inside wheel has a tighter turning Note: If you have no reason to suspect knuckle or angle than the outside wheel. This is “Ackerman spindle damage, checking the SAI is of lesser steer,” the result of the steering knuckle’s kingpin importance. If your Jeep rear axle is square with inclination, caster angle and the steering axis the frame and not bent, there is not a call for inclination (‘SAI’). Each of these variables affect thrust alignment. In the months ahead, I will share steering and the vehicle’s behavior when turning. information on how to easily set up a lift kit and Caster is often adjustable. When SAI is incorrect, adjust link arms to assure proper thrust and axle however, the most common cause is a damaged alignment with the frame. steering knuckle or bent spindle. Toe-Set

Toe-in is the most common measurement associated with front wheel alignment. Normal chassis and linkage wear, plus the characteristic pounding that 4x4s get on rough trails, make toe-set a periodic maintenance item.

Toe-in is the precise angle of the front wheels when the steering and wheels aim straight ahead. While parallel front wheels would seem ideal, the front wheels seldom call for zero-degrees of toe set.

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Due to the thrust loads of the vehicle moving type, bias-ply tires should follow factory alignment forward (especially with oversized tires!), and the specifications. That toe-in might be in the 1/16”- slight movement of steering joints under load, toe is 3/16” range, typically a 1/8” setting. actually set so that tires “toe-in” slightly. This toe-in If using modern radial tires, toe-in should be near is measurable at the forward side of the front tires. zero, something like 1/32” for stock tires. (Modern alignment is actually measured in tenths of a degree, not inches.) High-end alignment equipment can check toe-set with projectors and electronic beams. As you will see in this segment of “4WD Tech,” toe-in can also be checked with basic tools. Camber

With the chassis weighted and the front tires pointing straight ahead, each tire should stand nearly vertical. Viewed from the front of the vehicle,

camber degrees are the tilt of the tires, inward or The tires’ design dictates toe-in requirements. outward, from a vertical centerline. If the top of the Bias-ply tires have a tendency to thrust outward tire tilts outward, camber is “positive.” If the top of under load. The classic Willys or Jeep CJ with OEM the tire tilts inward, camber is “negative.”

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Alignment specifications read in positive or negative Jeep beam-type axles with leaf springs or link degrees of camber. arms have fixed camber. As the vehicle’s frame and body lean on corners, the axle stays parallel with the ground. With this design, there is no provision for adjusting the camber.* Unless the axle housing is bent, or worn ball-joints cause knuckle sagging, the axle maintains its original camber settings.

*Note: Camber can be corrected with aftermarket ball-joints or eccentric ball-stud seats. There is, however, no OEM provision for adjusting camber. By contrast, each front wheel on an IFS suspension moves up or down independently. Short (upper) and long (lower) control arm “SLA” suspension compensates for body/frame lean on corners.

As the vehicle corners, the body/frame rolls, Jeep Liberty “SLA” Front Wheel Suspension (Parts causing the outside wheels to compress the springs. illustration is courtesy of Chrysler/Jeep Corporation.) This moves the wheels upward into the fender

4WD Mechanix© Magazine…Issue #6, July 2010. For Fast Navigation, Use the Adobe Reader® “Bookmarks” Feature...There is a bookmark for each listed ‘Table of Contents’ item! wells. The unloading inside wheels drop as the body Solid, beam front axle Jeep vehicles have a rolls outward. A functioning sway bar helps simpler approach. As the frame/body rolls on turns, minimize this body/frame roll. the axle, wheels and tires stay parallel to the ground—unless we’re rock crawling with wheels in On SLA suspension like the Liberty, late Grand the air! The leaf springs or coil springs compress, as Cherokee or Commander, tire track width remains suspension allows for this roll. relatively constant during this process. The arc of wheel travel is precisely engineered for maximum As the outside wheel compresses the suspension, control and long tire life. the sway bar makes the vehicle squat—pulling the chassis downward, lessening the body/frame roll and lowering the center of gravity. The sway bar has a clear purpose, especially on the highway and when cornering at speed. Caster

Caster plays an important role in vehicle handling. Caster is the tilt of the kingpin or ball-joint centerlines when viewed from the side. Imagine a line drawn through center of the upper and lower

ball joints or kingpin/knuckle bearings (on a vintage

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Jeep). That is the kingpin centerline. The forward or well. If not, suspect a bent or defective spindle or rearward tilt of this centerline, measured in steering knuckle. degrees, is the caster angle. The typical front suspension calls for positive degrees of caster. Positive caster means that the upper end of the kingpin or ball-joint centerline tilts toward the rear of the vehicle. Caster has a very important function: helping the wheels come back to center after turns.

When there is too little caster angle, the most notable symptom is the need to actually steer the vehicle back to center. Correct caster settings also help steer the vehicle straight ahead, overcoming the effects of the road crown. (Camber plays a role Note that the kingpin or ball-joint centerline tilts here, too.) inward as well, but this is not caster. Inward tilt is Caster angle helps prevent pull and reduces the kingpin inclination, a measurement that affects the risk of kingpin or ball-joint shimmy. Some Jeep steering axis inclination (SAI). When caster and owners talk of this phenomenon as the “death camber are within specification, SAI should be as

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wobble” frequently associated with short-arm, link- consider caster, camber and toe-set. Changing the and-coil suspension lift kits that reduce caster angle. spring length or arch, changing the link arms, and other measures involved with lifting the chassis— each requires an alignment check and corrections. Every Jeep owner wants improved steering control, safe handling and maximum tire life. Performing your own wheel alignment and steering or suspension diagnostics can save money and bring a valuable resource into your shop or home garage. ‘SPC’ Makes Wheel Alignment Easy!

With a beam axle, it is possible to do on the spot

toe-set adjustments. Alongside the trail, I’ve set For the Jeep vehicle with a beam front axle, toe-in basic toe with nothing more than a tape measure is often the only adjustment needed if: 1) the frame and axle beam are straight, 2) the springs set and hand wrenches. For home use, a simple toe-bar evenly, 3) the knuckles and joints are in good and tire centerline scribe can be purchased through condition, 4) caster and camber meet specification. automotive tool suppliers.

Whether setting up a modified suspension or For an affordable, far more thorough approach, simply restoring your Jeep vehicle’s steering, always there is Specialty Products Company’s FasTrax®

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alignment equipment. The FasTrax® 91025 ‘Off- and after WWII, magnetic and clamp-on caster and Road’ alignment gauge kit provides a portable, fast camber gauges were common. These gauges with a and accurate way to measure toe-set, caster and simple toe-set bar and turn plates met garage, camber on vehicles with larger tire packages. dealership and body shop standards. In the right hands, these tools provided accurate wheel service for trucks, cars and, yes, the vintage Jeep vehicles.

I ran a modern Hunter alignment rack at a truck dealership in the early 1980s. Later, I taught wheel alignment techniques. $40K alignment systems with electronically controlled projection heads, drive-on racks, degree’d turn plates and computer stations are common today.

At less than 1% of that cost, SPC’s far simpler equipment targets the smaller commercial shops, home garages, fleet operators and racing teams. I

found the concept intriguing. As a budding mechanic in the ‘sixties, I was fascinated by the early wheel alignment equipment that was still in service. For decades, both before Copyright © 2010 by Moses Ludel…This material may be distributed solely by download from www.4WDmechanix.com. Please refer others to the website for a free download copy! Page 34

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I put the SPC Model 91025 Off-Road wheel alignment system to the test. In the process, I discovered that for safe handling, minimizing tire wear and customer satisfaction, this fast, accurate alignment equipment does the job! For four-wheelers who pound around on rocky trails or the 4WD shop that

regularly installs lift kits, wheels and The SPC 91025 package is a portable, accurate way tires, SPC offers a valuable tool. Used to check wheel alignment, including camber, caster properly, this is a practical alternative to and toe-set with the toe-arms shown. For large expensive trips to the alignment shop. As tires, this is the kit. As an ancillary benefit, the equipment also serves as a quick diagnostic tool. you will see, it is also a useful diagnostic Use of these tools saves both time and money! and troubleshooting tool…

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2: The use of sheet plastic beneath each tire is a budget conscious alternative to turn plates. (If you can afford turn plates, get them.) Plastic reduces friction while turning the wheels left-straight-right. Set the FasTrax® base just outboard and square with the tire’s face. Level the bubble to “0” on the camber scale as shown below.

1: To demonstrate a home-like setting, I parked the XJ Cherokee on a recently poured driveway slab. The FasTrax® 91025 comes with a floor calibrated base. Since the aim is to read angles on a bubble level gauge, the level must be parallel to the floor at each wheel. Here, I set a level on the slab just to get a sense for the floor’s level. (The gauges can work on an uneven surface.) Begin the alignment with the front wheels straight ahead…

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4: When mounting the 3-arm fixture, a straight- edged spirit level helps align the gauge vertically. This assures accuracy, as the gauge is now on plane vertically and horizontally. The first measurement, with the wheels pointed precisely straight ahead, is camber. This is a beam axle in apparent good condition; camber should be a non- issue. I quickly find this not to be the case, though!

3: The two arms that come with the 91025 Off- Road kit are for toe-set. I placed them on the gauge assembly before mounting the fixture on the wheel. The 3-point fixture clamped internally, tightened with the rack gear and knob system on the fixture. American Racing wheels have spot-on machining, which makes it easy to center the gauge fixture and know that the gauge sets true.

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5: Wow, minus 3-degrees (negative) camber! Factory setting is minus 0.25-degrees with a range or tolerance of 0.75-degrees negative to 0.5- degrees positive. This is the right side wheel, which tolerates a bit of extra camber, however, there’s still an extra 2.25-degrees negative. The spirit level (below) is square with the ground and reveals the negative camber situation graphically. Some jump to the conclusion that this reflects a bent axle housing, but there are other possibilities.

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6: Five minutes into the process, the SPC alignment gauge served as a precise diagnostic tool for front end troubles! The excess negative camber reflects a tilting steering knuckle. This could be caused by a bent axle housing, but the history of this vehicle does not suggest that kind of trouble. (Yes, the Dana axles do run to the limit of tolerance, sometimes even exceeding it, so some of this error could be inherent to the axle beam.) Considering the vehicle’s 122K miles and the use of large tires with shallower wheel backspacing than stock, there is plenty of loading on the knuckle ball joints. These are the original joints. If loose, the natural slant of the knuckle will be negative degrees, just like the reading found here. So, before scrapping out an axle housing (although a Dana 44 would be nice!), I will jack up each side of the axle beam and check the ball-joints for wear or looseness. For the record, this vehicle steers quite nicely, without signs of wobble…Thanks, SPC alignment gauge, for the useful diagnostics!

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8: The engine needed to be fired to apply power steering and turn the wheels. At the right side of the vehicle, I began with a turn right, 15-degrees. Here, the alignment gauge is parallel with the 15- degree line on the protractor. In that position, set the bubble level on the SPC gauge to a precise “0” along the caster scale.

7: Accurately checking caster without turn plates does require innovation! The system calls for turning the wheels 15-degrees each way from center (straight ahead) during caster check. Opting for the “plastic bag” approach, I placed the straight-edge (on ground) parallel with the tire. Then I placed a protractor, set at fifteen degrees,

square with the straight edge. The idea is to provide an accurate reference line.

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10: The bubble is very clearly at 7.5-degrees positive caster. (Zoom-in for detail!) This clear measurement is excellent. Factory preferred caster is 7.0-degrees positive. Range is 5.25-degrees positive to 8.5-degrees positive. Caster provides the desired return-to-center, and this XJ Cherokee has been easy to drive and steer…Straighten the steering to center (straight ahead). Now move the gauge assembly to the left front wheel.

9: Now turn the front wheels left to an angle of 15-degrees left of the straight ahead position…At this point, the right wheel’s caster will read in degrees along the caster scale of the bubble gauge.

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12: The gauge mounts squarely, shouldered evenly against the wheel rim. Avoid clamping the fixture at rim sections with wheel weights or abrasions that might distort the angle. I again use the straight-edge spirit level to align the fixture vertically. Once the fixture is squarely mounted to the wheel, you can read camber on the gauge.

11: At the left front wheel, the gauge is set flatly on the ground, just outboard of the wheel/tire. Zero the bubble gauge on the Fastrax® 91025 gauge. Carefully raise the gauge into position and mount it on the wheel rim. Handle the fixture as you would a precision instrument and do not

disturb the bubble gauge when clamping the assembly onto the wheel.

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housing or knuckle can cause negative camber, there is no evidence to support that kind of abuse. Likely culprit is worn ball joints. Discoveries like this more than pay for the FasTrax® tool!

14: Caster can now be checked on the left side. Wheels pointed straight ahead, the straight-edge is set parallel to the tire. Once again, the protractor provides the line for 15-degrees of left turn angle.

13: Read the left side camber measurement. (You can zoom-in for detail.) This side reads nearly 2.5- degrees negative camber, well beyond the OEM limits of 0.75-degrees negative. Note: At 20,000-plus miles on these tires, wear is uniform and nominal. Tire rotation at 5K-7K miles has minimized wear. Despite the poor camber readings, the vehicle steers well. This camber check has exposed a vital concern. While a bent axle

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without using the steering wheel. SPC offers turn plates. Consider them!

16: Once again, turn the wheels out 15-degrees. (This is the left/driver’s side, so turn left.) At the turned out position, move the bubble gauge to “0” on the caster scale.

15: Protractor set to 15-degrees left of the straight ahead wheel position, turn wheels until the bubble gauge is exactly parallel to the 15- degree line of the protractor. Note: Turn plates would be helpful. Plates have detailed degree marks and a pointer. They allow the front wheels and tires to “float,” relieving thrust pressure and allowing easy left-to-right turning of the wheels. On turn plates, wheels can be turned left and right (gripping the tires)

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18: Now the final reading for caster. With the front wheels turned 15-degrees right, the caster sweep measurement is exactly 7 degrees positive caster. The caster at each side reads well within specification. Factory allowance is a maximum right-to-left “difference” of 1.25-degrees. Actual caster measurements are within 0.5-degrees of each other. This is optimal.

17: Here is the left front wheel turned outward to the 15-degree point. Note that the bubble gauge has been set to read “0” on the “Caster Sweep” 15- degree scale. The gauge is very clear and responsive. I am confident that for Jeep vehicles, especially with a beam axle, this is a reliable approach. In addition to alignment, the tool demystifies front end, steering and axle troubles.

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Factory Front Wheel Alignment Specs for an ’05 TJ Wrangler—An Example of Beam Axle Limits for a Popular Jeep 4x4:

PREFERRED CASTER: + 7.0° ±1.0° CAMBER (fixed angle): 0.25° Negative ± 0.63° TOTAL TOE-IN: 0.15° (each front wheel) ±0.06° MAX RT/LT DIFFERENCE: Caster: 0.65° Camber: ±1.0° Toe-in: .06°

The Rear Axle Also Has Preferred OEM Alignment Specifications, Measurable With 19: Reading is 7-degree positive caster at the left front wheel. With these figures, steering is safe and the SPC FasTrax® Gauges: positive with optimal return to center feel. Caster CASTER: Not Applicable. The only concern is pinion dictates the driveline pinion angle. On vintage Jeep angle for U-joint alignment. vehicles with single-Cardan U-joints, front end CAMBER: –0.25° with 0° to –.50° Allowable caster is less. This reduces the angle of the front U- TOTAL TOE-IN: 0.25° with 0° to 0.5° Allowable joint. Early Jeep axles call for 4-degrees positive THRUST ANGLE 0° ± 0.25° caster. Chart at left depicts a late-model Wrangler with an OEM, double-Cardan (CV) joint at one end of the front driveshaft. Note use of more caster.

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20: For setting toe-in, turn front wheels directly back to straight ahead. The two wing arms on the 91025 system have slots for various diameter tires. Designed for off-road vehicles, there are slots that match the oversized, 33” tires on the XJ Cherokee. I like to measure toe as close to the horizontal centerline of the tires as practical. Make sure that the tape can cross to the opposite side without bowing or hitting obstructions. Keep tape parallel to the ground and just outboard of tire tread.

21: For toe-set, the tape goes straight across to the passenger side tire. Measure width at the rear and front of the tires. The difference is toe. Shorter at the front than rear is “toe-in.” Shorter at the rear of the tires is “toe-out.” Stock radial tires call for “0-degrees” toe on this XJ Cherokee. With large tires, wide rims, shallower back-spacing and lots of unsprung weight mass, these tires will naturally toe outward as the vehicle moves forward. From experience, I set a toe-in of 3/32” to compensate. Copyright © 2010 by Moses Ludel…This material may be distributed solely by download from www.4WDmechanix.com. Please refer others to the website for a free download copy! Page 47

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22: Some use two 91025 kits and measure between the four toe arms. With one kit, toe is measured from the left side arms to either a scribed centerline at the right side tire or a common tread pattern point. Here, a reference point is established at the rear of the right front tire. Remove tape slack but do not pull hard. The extended toe arms will bow if you apply too much pressure. For accuracy, match the tape tension at the front and rear measurement points.

23: While some place the toe arms near the floor, I set the FasTrax® toe arms near the middle of the tire. The tape parallel with the ground, reach across to the opposite tire. Pick the exact same tire pattern point at the front of the tire, and measure the distance. In this case, the front measurement is slightly shorter as desired. This is toe-in. Note: Picking a matching tread point can be tricky. You want the tape as level as possible. Make sure the tread reference points are identical at the front and rear. Copyright © 2010 by Moses Ludel…This material may be distributed solely by download from www.4WDmechanix.com. Please refer others to the website for a free download copy! Page 48

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Footnote: Aligning the Steering Wheel to Center 24: At the front side of the tire, Steering Wheel Alignment When aligning the front wheels, make sure the the measurement is 72-1/8”. At steering wheel aligns with the steering gear’s center the rear, the measurement to point. If the steering wheel aligns with the gear’s the same tread pattern point center point, do not remove and reposition the was slightly under 72-1/4”. This steering wheel to center it during wheel alignment. is a difference of 3/32”—shorter Instead, point the front wheels straight ahead. at the front side of the front After adjusting toe, center the steering wheel by tires. The front measurement is adjusting the tie rods or draglink. Road test and readjust again if necessary. Do not change the toe shorter, so this wheel alignment setting in the process. Re-check toe-in if necessary. has “toe-in.” Slight toe-in will The only Jeep vehicles that require repositioning work well for the tire size and the steering wheel are early model Willys trucks vehicle’s weight distribution equipped with a non-adjustable, fixed length drag with the heavy winch/bumper link. On these models, the steering gear must still out front. be very close to its center point (over-center high point) when the front wheels point straight ahead.

Adjusted properly, the steering wheel should be on center with the front wheels steering straight ahead. The steering gear should be at its over- Sierra Stomper Dan Wilson took his center high point (midway between left and right 1988 XJ Cherokee on trail last week. turning extremes) when the front wheels point SPC’s FasTrax® 91025 gauges would straight ahead. By design, this will provide the least be a valuable tool at Dan’s home amount of steering backlash or play when the vehicle steers straight down the road. shop! (Photo courtesy of Dan Wilson.)

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Moses Ludel Evaluates the FasTrax® 91015 Caster/Camber/Toe Gauge

The Specialty Products Company’s Model 91025 alignment kit works very well. Portable and light weight, the quality gauge construction maintains calibration and tolerance. Alignment chores are easy with this kit. The design incorporates proven features like a bubble caster and camber gauge. A precisely machined, gear drive clamping fixture, attractively anodized, will deliver quality service over time.

SPC’s 91025 FasTrax® kit for Off-Road vehicles is an optimal investment for the aftermarket suspension installation shop or any serious racer/trail runner who wants maximum handling and performance from a 4x4.

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This is a useful troubleshooting tool as well, capable of quickly revealing suspension, live beam axle and steering system damage.

Unless you have the shop space and an unlimited budget for electronic alignment equipment and a four- wheel alignment rack, consider the FasTrax® 91025 a cost-effective, sensible alternative. Accurate, portable and designed to set up quickly on any flat surface, Specialty Products Company’s FasTrax® 91025 should be a fixture at the garage and pit area of every off-road race crew. Serious trail runners and any Jeep owner who does his or her own service work will find this tool valuable. Save tires, save time and diagnose trouble at the earliest point with this versatile tool. For the fleet truck shop with a service and preventive care program, the FasTrax® could pay for itself in a week!

Specializing in niche suspension and steering parts for Jeep 4WDs, popular trucks, SUVs, passenger cars and off-road racing vehicles, SPC offers offset ball-joints and eccentric seats for adjusting caster and camber. The catalog features unique alignment shims and eccentric bolts for adjusting link arms, plus coil spring spacers and bushings. SPC builds a variety of specialty tools and features a “Light Racing” parts program, popular among rock crawlers and Baja-type desert racers.‘SPC’ offers a video that demonstrates 91000-series FasTrax® tools in operation: http://www.spc-tv.com/install/tools/40-91000.html. In business since 1972, Specialty Products Company should be on your “Favorites” list! Check out their product line. Download the SPC catalogs for more information:

http://www.specprod.com/CATALOG_DIR/CATALOG_INTRO.HTML.

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