Alignment: Service and Repair
Wheel Alignment Overview
Front wheel alignment is the proper adjustment of all the interrelated suspension angles affecting the running and steering of the front wheels of the vehicle. The importance of wheel alignment and wheel balancing is considered essential in order to maintain ease of steering, good directional stability and to prevent abnormal tire wear.
Under every day driving conditions the front wheel alignment angles change and therefore it becomes necessary that every vehicle should have an alignment check at least once a year. Such an inspection of the front suspension and steering components is a preventative maintenance service and also has a definite bearing on the safe operation of the vehicle.
The method of checking front wheel alignment will vary depending on the type of equipment being used. The instructions furnished by the manufacturer of the equipment should always be followed, with the exception that the specifications as recommended by the vehicle manufacturer should always be used.
Fig. 1 Wheel Alignment Measurements:
There are five basic factors (measurements) which are the foundation to front wheel alignment; caster, camber, toe-in, steering axis inclination and toe-out on turns.
All are mechanically adjustable except steering axis inclination and toe-out on turns. These two are valuable in determining if the parts are bent or damaged particularly when the camber and caster adjustments cannot be brought within the recommended specifications.
CAUTION: DO NOT ATTEMPT TO MODIFY ANY SUSPENSION OR STEERING COMPONENTS BY HEATING OR BENDING.
All adjustments/modifications should be made in the following sequence:
a. Caster and Camber.
b. Toe-in.
c. Steering Axis Inclination. (Not Adjustable, replacement only)
d. Toe-out on Turns. (Not Adjustable, replacement only)
Caster is the number of degrees of forward or backward tilt of the spindle support arm at the top. Forward tilt of the spindle support arm at the top is negative caster. Backward tilt of the spindle support arm at the top from true vertical is positive caster.
Camber is the number of degrees the top of the wheel is tilted inward or outward from a true vertical. Inward tilt of the top of the wheel from true vertical is negative camber. Outward tilt of the wheel at the top is positive camber. Excessive camber is a tire wear factor; negative camber causes wear on the inside of the tire, while positive camber causes wear to the outside.
Toe-in is measured in inches and is the distance the leading edges of the tires are closer than the trailing edges. Toe-in is considered the most serious cause for excessive tire wear. Toe-in is the last of the alignment angles to be set in the front wheel alignment operation.
Steering Axis Inclination is measured in degrees and is the amount the spindle support center line is tilted from true vertical. It has a fixed relationship with camber settings and does not change except when a spindle or ball joint is damaged or bent. This angle is not adjustable and damaged parts must be replaced.
Toe-Out on Turns (Turning Radius) is measured in degrees and is the amount one front wheel turns sharper than the other on a turn. This angle is designed into the steering arm in relationship to the wheelbase of the vehicle and is not adjustable. When checking the turning radius and it is found not to be within the recommended specifications, look for possible bent or damaged components.
Pre-Alignment Inspection
Before any attempt is made to change or correct the wheel alignment factors the following inspection and necessary corrections must be made on those parts which influence the steering of the vehicle.
1. Check and inflate tires to recommended pressure. All tires should be the same size and be in good condition and have approximately same wear. Make a note of the type of tire tread wear which will aid in diagnosing.
2. Check and adjust front wheel bearings.
3. Check front wheel and tire assembly for radial and lateral runout (follow the Equipment Manufacturers Instruction).
4. Check wheel and tire for unbalance conditions both static and dynamic which could affect steering.
5. Inspect ball joints and all steering linkage pivot points for excessive looseness.
6. Check shock absorbers for leaks and jounce vehicle to determine if shock absorbers have proper control.
7. Check steering gear for roughness, binding or sticking condition and adjust as necessary.
8. Check rear springs for cracks or broken leaves and U-bolts for proper tightness and measure height differential between left and right sides of vehicle. (Vehicle should be on level floor or on alignment rack) with a full tank of fuel and no luggage or passenger load.
Note: To obtain accurate readings, vehicle should be jounced in following manner just prior to taking each measurement (Caster-Camber and Toe): Grasp bumpers at center (rear bumper first) and jounce up and down several times. Always release bumpers on the down cycle after jouncing both rear and front ends an equal number of times.
Specifications:
Front wheel alignment settings must be held to specifications to hold tire wear to a minimum and to maintain steering ease and handling of vehicle.
The equipment manufacturers recommended procedure should always be followed. Any parts of the front suspension system should be replaced if they are found to be bent.
CAUTION: DO NOT ATTEMPT TO STRAIGHTEN ANY BENT PART.
1. Prepare vehicle for measuring wheel alignment.
2. Remove all foreign material from exposed threads of cam adjusting bolts.
3. Record initial camber and caster readings before loosening cam bolt nuts.
4. Camber settings should be held as close as possible to the "preferred" setting. Caster should be held as nearly equal as possible on both wheels. See specifications.
The toe setting should be the final operation of the front wheel alignment adjustments. The front wheels must be in a straight ahead position. Follow the equipment manufacturers procedure. The steering wheel should also be centered during this operation.
Turning the tie rod sleeve will "center" the steering wheel spokes. If the steering wheel was centered, make the toe-in adjustment by turning both sleeves an equal amount.