CAMBER
Camber is inward or outward tilt of top of tire and wheel assembly. (Scheme 2) Camber is measured in degrees of angle relative to a true vertical line. Camber is a tire wearing angle and can cause the following wear
- Excessive negative camber will cause tread wear on inside of tire.
- Excessive positive camber will cause tread wear on outside of tire.
Scheme 2
CROSS CAMBER
Cross camber is difference between left and right camber. To achieve cross camber reading, subtract right side camber reading from left. For example, if left camber is plus 0.3 degrees and right camber is 0.0 degrees, cross camber would be plus 0.3 degrees.
CASTER
Caster is forward or rearward tilt of steering knuckle in reference to position of upper and lower ball joints. Caster is measured in degrees of angle relative to a true vertical center line. This line is viewed from side of tire and wheel assembly. (Scheme 2)
- Forward tilt (upper ball joint ahead of lower) results in a negative caster angle.
- Rearward tilt (upper ball joint trailing lower) results in a positive caster angle.
Although caster does not affect tire wear, a caster imbalance between 2 front wheels may cause vehicle to lead to side with least positive caster.
CROSS CASTER
Cross caster is difference between left and right caster.
TOE
Toe is inward or outward angle of wheels as viewed from above vehicle. (Scheme 2)
- Toe-in is produced when front edges of wheels on same axle are closer together than rear edges.
- Toe-out is produced when front edges of wheels on same axle are farther apart than rear edges.
- Toe-in and toe-out can occur at front wheels and rear wheels. Toe is measured in degrees or inches. The measurement identifies amount that front of wheels point inward (toe-in) or outward (toe-out). Toe is measured at spindle height. Zero toe means front and rear edges of wheels on same axle are equally distant.
TOE-OUT ON TURNS
Toe-out on turns is relative positioning of front wheels while steering through a turn. (Scheme 3) This compensates for each front wheel's turning radius. As vehicle encounters a turn, outboard wheel must travel in a larger radius circle than inboard wheel. The steering system is designed to make each wheel follow its particular radius circle. To accomplish this, front wheels must progressively toe outward as steering is turned from center. This eliminates tire scrubbing and undue tire wear when steering a vehicle through a turn.
Scheme 3
STEERING AXIS INCLINATION (S.A.I.)
Steering axis inclination is angle between a true vertical line starting at center of tire at road contact point and a line drawn through center of upper ball joint (or strut) and lower ball joint. (Scheme 4) S.A.I. is built into vehicle and is not an adjustable angle. If S.A.I. is not within specifications, a bent or damaged suspension component may be cause.
Scheme 4
INCLUDED ANGLE
Included angle is sum of S.A.I. angle plus or minus camber angle, depending on whether or not wheel has positive or negative camber. (Scheme 4) If camber is positive, add camber angle to S.A.I. angle. If camber is negative, subtract camber angle from S.A.I. angle. Included angle is not adjustable, but can be used to diagnose a frame misalignment or bent suspension component (spindle, strut).
THRUST ANGLE
Thrust angle is averaged direction rear wheels are pointing in relation to vehicle's center line. (Scheme 5) The presence of negative or positive thrust angle causes rear tires to track improperly to left or right of front tires (dog tracking) in the following manner
- Negative thrust angle means rear tires are tracking to left of front tires.
- Positive thrust angle means rear tires are tracking to right of front tires.
Improper tracking can cause undue tire wear, a lead or pull and a crooked steering wheel.
Scheme 5
Scheme 6
Scheme 7
STANDARD PROCEDURE
Note. Before starting a wheel alignment on this vehicle, following inspection and necessary corrections must be completed to ensure proper wheel alignment.
- The passenger and luggage compartments of vehicle should be free of any load that is not factory equipment. Check tires on vehicle. The tires are to be inflated to recommended air pressure. All tires must be correct size and in good condition, with about same tread wear.
- Check front and rear wheels for excessive radial and lateral runout, and imbalance. Inspect front and rear hub and bearing assemblies for wear and noise. Inspect all suspension components for wear. Check components for correct torque. Inspect rubber bushings on all suspension components for signs of wear or deterioration.
- Inspect control arm ball joints and steering linkage for leaking seals, looseness, roughness, binding or a sticking condition. Inspect front and rear shock assemblies for leaks or any sign of damage. Jounce front and rear of vehicle to determine if shock absorbers dampen vehicle motion properly.
FRONT SUSPENSION HEIGHT
Vehicle front suspension height must be measured and adjusted before performing wheel alignment. Procedure must also be performed when front suspension components are replaced. Measurement is taken on both sides with vehicle supporting it's own weight.
Measurement Procedure
- Remove any load within passenger and luggage compartments that is not factory equipment. Place vehicle on wheel alignment rack or drive-on lift per equipment manufacturer's recommendations. Check all tires for proper inflation pressure and adjust as necessary.
- Jounce front of vehicle several times. Measure and record distance between center of lower suspension arm rear mounting bolt and surface front tire is sitting on. Measure and record distance between center of front wheel and surface front tire is sitting on. see scheme 7
- Subtract first measurement from second measurement. Difference between 2 measurements should be 3.19" (81 mm), plus or minus.126" (3.20 mm). If front suspension height is not within specifications, go to «ADJUSTMENT PROCEDURE»(ref-167530-S20997530112004101500000).
- Remove any load within passenger and luggage compartments that is not factory equipment. Place vehicle on wheel alignment rack or drive-on lift per equipment manufacturer's recommendations. Check all tires for proper inflation pressure and adjust as necessary.
- Jounce front of vehicle several times. Measure and record distance between rear jounce bumper on the axle side to the jounce bumper cup lip on the frame side.
- Subtract first measurement from second measurement. Difference between 2 measurements should be 6.06" (154 mm) plus or minus .39" (10 mm) for vehicles with 8.25" axle, or 5.83" (148 mm) plus or minus .39" (10 mm) for vehicles with 9.25" axle.
- If rear suspension height is not within specifications, inspect all rear suspension components for wear or damage. Repair or replace components as necessary. Recheck vehicle height.
FLOOR JACK
| CAUTION | Never place jack under any part of vehicle underbody. DO NOT attempt to raise one entire side of vehicle by placing a jack midway between front and rear wheels, as permanent body damage could occur. Do not position hoist on an axle tube or aluminum differential. |
Raise front end by placing floor jack under vehicle as shown. (Scheme 8) To raise rear end, place floor jack under rear axle, next to leaf spring mount. Support vehicle with jack stands at front and rear ends of frame.
Scheme 8
EMERGENCY JACKING
Place scissor jack under front frame rail behind wheel. Locate jack as far forward as possible on straight part of frame. When changing rear tire, place jack under axle between spring and shock absorber. Always block opposite wheels, and jack on level surface.
BUMPER JACK
| WARNING | DO NOT attempt to raise vehicle with bumper jack. Personal injury and/or vehicle damage could result. |
HOIST
| CAUTION | If removing engine, rear axle, fuel tank, spare tire or liftgate and a single-post hoist is used, anchor vehicle to hoist. To prevent tipping when center of gravity shifts, place jack stands under vehicle or add weight on rear end of vehicle. |
Frame Contact Hoist
Frame contact hoist must be equipped with proper adapters to support vehicle in correct locations. If using swiveling arm hoist, position lifting pads evenly on subframe rails. Hoist must be equipped with proper adapters so vehicle will be supported at marked points.
Vehicle may be raised on single or twin post swiveling arm type hoists. If using swiveling arm hoist, ensure lifting arms, pads or ramps are positioned evenly on frame rails, and adequate clearance is maintained for transfer case (4WD models) or skid plate. All hoists must be equipped with adapters to properly support vehicle. (Scheme 8)
Axle Contact Hoist
DO NOT use axle contact hoist. Damage to axle tube or aluminum differential will occur.
CAMBER & CASTER ANGLE
Note. Vehicle suspension height must be checked and adjusted to preferred specifications prior to performing wheel alignment. See appropriate procedure under RIDE HEIGHT ADJUSTMENT .
Camber and caster angle adjustments involve changing the position of the lower control arm using slots in frame brackets to move the lower control arm inward or outward for proper adjustment. This can be achieved by using a long pry bar with a curved tip, and inserting the pry bar into the lower control arm frame brackets and prying inward or outward.
Note. When lower control arm pivot bolts are loosened, lower control arm will normally go outward automatically with the weight of the vehicle.
To adjust camber, move both front and rear of lower control arm together in and out. This will change camber angle significantly and caster angle slightly. (Scheme 9) For wheel alignment specifications, see ALIGNMENT SPECIFICATIONS. After adjustment is made, tighten lower control arm nut to specification. See TORQUE SPECIFICATIONS.
- Caster can be adjusted by moving the rear position of the lower control arm at the frame in or out. This will change caster angle significantly and camber angle slightly. To maintain camber angle while adjusting caster, move the rear of the lower control arm in or out. (Scheme 9)
- Then move the front of the lower control arm slightly in opposite direction. For wheel alignment specifications, see «ALIGNMENT SPECIFICATIONS»(ref-167530-S06619146452004101500000). After adjustment is made, tighten lower control arm nut to specification. See «TORQUE SPECIFICATIONS»(ref-167530-S20038422032004101500000).
Scheme 9
FRONT TOE
Note. Vehicle suspension height must be checked and adjusted to preferred specifications prior to performing wheel alignment.
Note. Set each front wheel at 1/2 of total toe specification. On vehicles equipped with power steering, set wheel toe position with engine running.
Center steering wheel and hold with steering wheel clamp. Loosen tie rod lock nuts. Rotate tie rods to set toe to specification. (Scheme 10) For wheel alignment specifications, see ALIGNMENT SPECIFICATIONS. Tighten tie rod lock nuts to specification. See TORQUE SPECIFICATIONS. Adjust steering gear to tie rod boots at tie rod. Remove steering wheel clamp. Road test vehicle to verify steering wheel is straight and vehicle does not wander or pull.