Proper alignment of the front wheels must be maintained in order to ensure ease of steering and satisfactory tire life.
The most important factors of front wheel alignment are wheel camber, axle caster, and wheel toe-in.
Wheel toe-in is the distance by which the wheels are closer together at the front than at the rear.
Wheel camber is the amount the top of the wheels incline outward from the vertical.
Front axle caster is the amount in degrees that the steering pivot pins are tilted toward the rear of the vehicle. Positive caster is inclination of the top of the pivot pin toward the rear of the vehicle.
These points should be checked at regular intervals, particularly when the front axle has been subjected to a heavy impact. When checking wheel alignment, it is important that wheel bearings be in proper adjustment. Loose bearings will affect instrument readings when checking the camber, pivot pin inclination, and toe-in.
Front wheel camber is preset. Some alignment shops can correct camber to some extent by installing special tapered shims between the steering knuckle and the spindle.
Caster is also preset, but can be altered by use of tapered shims between the axle pad and the springs. Wheel toe-in is adjustable.
To avoid damage to the U-joints, it is advisable to check the turning angle periodically. An adjustment turntable is advisable for properly determining the angle.Correct turning angles are:
To adjust the turning angle, loosen the locknut (on some early models, a securing weld will have to be broken) and turn the adjusting screw. The adjusting screw is located on the axle tube near the knuckle on early models, and on the knuckle, just below the axle centerline on later models.
See Figure 1
Caster angle is established in the axle design by tilting the top of the kingpins forward so that an imaginary line through the center of the kingpins would strike the ground at a point ahead of the point of the contact.
The purpose of caster is to provide steering stability which will keep the front wheels in the straight ahead position and also assist in straightening up the wheels when coming out of a turn.
If the angle of caster, when accurately measured, is found to be incorrect, correct it to the specification given in this section by either installing new parts or installing caster shims between the axle pad and the springs.
If the camber and toe-in are correct and it is known that the axle is not twisted, a satisfactory check may be made by testing the vehicle on the road. Before road testing, make sure all tires are properly inflated, being particularly careful that both front tires are inflated to exactly the same pressure.
If the vehicle turns easily to either side but is hard to straighten out, insufficient caster for easy handling of the vehicle is indicated. If correction is necessary, it can usually be accomplished by installing shims between the springs and axle pads to secure the desired result.
See Figure 2
The purpose of camber is to more nearly place the weight of the vehicle over the tire contact patch on the road to facilitate ease of steering. The result of excessive camber is irregular wear of the tires on the outside shoulders and is usually cau