Wheel Alignment: Caster/Camber Adjustment

Caster affects steering stability and steering wheel returnability. Zero (0) caster is present when the upper ball joint or top strut bearing and lower ball joint are in the same plane as viewed from the side of the vehicle. Positive caster exists when the upper ball joint or top strut bearing is toward the rear of the vehicle in relationship to the lower ball joint. When the upper ball joint or top strut bearing is toward the front of the vehicle in relationship to the lower ball joint, negative caster is present. If the caster at both wheels is not equal, the vehicle will tend to drift toward the side with the lowest caster.

Examples of the screens available on the latest alignment machines.

Camber is the inward or outward tilt of the top of the wheel. Adjusting camber centers the vehicle’s weight on the tire. Proper camber adjustment minimizes
tire wear. Zero (0) camber is present when the wheel is at a perfectly vertical position. The tires have positive camber when the top of the tire is tilted out, or away from the engine. When the top of the tire is tilted in, there is negative camber. Incorrect camber will cause excessive stress and wear on suspension parts. Too much negative camber will cause wear on the inside tread of the tire, whereas too much positive camber will cause tire wear on the outside tread. If camber is not the same on both wheels, the vehicle will pull toward the side with the most positive camber.

Adjusting Caster and Camber
Several methods are used to adjust caster and camber; always check the service information to determine how the alignment angles can be changed. Most current wheel alignment machines feature illustrations, pictures, or videos of what should happen and where.
Camber on nearly all front suspensions is adjustable, although installing special bolts or making modifications to the strut or knuckle may be needed. On strut-equipped vehicles, camber can be adjusted by moving the top of the strut mount or by adjusting an eccentric bolt located where the strut attaches to the steering knuckle. Caster is adjustable on some strut-equipped vehicles. This is done by again moving the top of the strut. Typically, there is no provision for adjusting caster. Vehicles that have no simple means for adjusting camber or caster require the installation of special kits from the aftermarket to obtain the correct angles. These kits basically contain an adjustable strut mount that permits the top of the strut to move front to back and left to right.
On other vehicles, the upper or lower control arm is used to adjust camber and caster. This is done by adding or removing shims between the control arm and the frame or by rotating an eccentric shaft or eccentric washers. Two bolts attach the control arm to the frame. An equal amount of shims is placed behind or in front of both bolts to correct camber. To gain more negative camber, the lower control arm must be moved outward or the upper arm moved inward. The opposite is true for gaining positive camber.
Caster is adjustable on all vehicles with an upper and a lower control arm. This is done by rotating an eccentric bushing at one of the pivot points for the control arm or adding or subtracting shims between a control arm and the frame.
Rear-wheel camber may be adjustable. When it is, camber is adjusted by eccentric bushings at the control arm pivot point or by an eccentric on the lower mounting of the strut. Solid rear axles seldom have a provision for camber adjustment.

Shims
Many cars use shims for adjusting caster and camber. The shims can be located between the control arm pivot shaft and the inside of the frame. Both caster and camber can be adjusted in one operation requiring the loosening of the shim bolts just once. Caster is changed by adding or subtracting shims from one end of the pivot shaft only. Then, camber is adjusted by adding or subtracting an equal amount of shims from the front and rear bolts. This procedure allows camber to change without affecting the caster setting. Some cars use shims located between the control arm pivot shaft and the outside of the frame. The adjustment procedure is the same as just described. Always look at the shim arrangements to determine the desired direction of change before loosening the bolts.

Adding and subtracting shims between the control arm and the frame will change caster and camber.

Eccentrics and Shims
Eccentrics and shims are used on some vehicles to adjust caster and camber. In some designs, an eccentric bolt and cam on the upper control arm adjust both caster and camber. To adjust, the nuts on the upper control arm are loosened first. Then, one eccentric bolt at a time is turned to set caster. Both bolts are turned equally to set camber.
The eccentric bolt and cam assembly can be located on the inner lower or upper control arm. Unlike other designs, camber is adjusted first. Some car models have a camber eccentric between the steering knuckle and the upper control arm. The camber eccentric is rotated to set camber. Caster is set with an adjustable strut rod.

Eccentric bolt and cam, shown on an upper control arm.

Graduated cam for adjusting camber.

Slotted Frame
The slotted frame adjustment has slotted holes under the control arm inner shaft that allow the shaft to be repositioned to the correct caster and camber settings. Caster and camber adjusting tools help in making adjustments. One end of the shaft is moved for caster adjustment. Both ends of the shaft are moved for camber adjustment. Turning a nut on one end of the rod changes its length and adjusts caster. Camber is set by an eccentric at the inner end of the lower control arm, or by a camber eccentric in the steering knuckle of the upper support arm, as described earlier.

Ball Joint Stud Bushings
Some suspension systems have an eccentric bushing at the top of the steering knuckle. This bushing can be used to adjust camber and camber. The bore for the ball joint stud through the bushing is offcenter. Rotating the bushing moves the wheel’s geometry. If the correct alignment cannot be attained by rotating the bushing, replacement bushings are available. You will need to obtain a bushing that changes the caster and/or camber specific amounts.