Front wheel alignment is the position of the front wheels relative to each other and to the vehicle. It is determined and must be maintained to provide safe, accurate steering with minimum tire wear. Many factors are involved in wheel alignment and adjustments are provided to return those that might change due to normal wear to their original value. The factors which determine wheel alignment are dependent on one another; therefore, when one of the factors is adjusted, the others must be adjusted to compensate.
The procedure for checking and adjusting front wheel alignment requires specialized equipment and professional skills. The following descriptions are for general reference only.
Descriptions of these factors and their affects on the car are provided below.
Do not attempt to check and adjust the front wheel alignment without first making a thorough inspection of the front suspension components.
See Figure 1
Camber angle is the number of degrees that the centerline of the wheel is inclined from the vertical. Camber reduces loading of the outer wheel bearing and improves the tire contact patch while cornering.
See Figure 2
Caster angle is the number of degrees that a line drawn through the steering knuckle pivots is inclined from the vertical toward the front or rear of the car. Caster improves directional stability and decreases susceptability to crosswinds or road surface deviations.
STEERING AXIS INCLINATION
Steering axis inclination is the number of degrees that a line drawn through the steering knuckle pivots is inclined to the vertical, when viewed from the front of the car. This, in combination with caster, is responsible for directional stability and self-centering of the steering. As the steering knuckle swings from lock to lock, the spindle generates an arc, the high point being the straight-ahead position of the wheel. Due to this arc, as the wheel turns, the front of the car is raised. The weight of the car acts against this lift, and attempts to return the spindle to the high point of the arc, resulting in self-centering when the steering wheel is released, and straightline stability.
See Figures 3 and 4
Toe-in is the difference of the distance between the center and rear of the front wheels. It is most commonly measured in inches, but is occasionally referred to as an angle between the wheels. Toe-in is necessary to compensate for the tendency of the wheels to deflect rearward while in motion. Due to this tendency, the wheels of a vehicle with properly adjusted toe-in are traveling straight forward when the vehicle itself is traveling straight forward, resulting in directional stability and minimum tire wear.
Steering wheel spoke misalignment is often an indication of incorrect front end alignment. Care should be exercised when aligning the front end to maintain steering wheel spoke position. When adjusting the tie-rod ends, adjust each an equal amount (in the opposite direction) to increase or decrease toe-in. If, following the toe-in adjustment, further adjustments are necessary to center the steering wheel spokes, adjust the tie-rod ends an equal amount in the same direction.
ADJUSTMENT OF CASTER, CAMBER, & TOE-IN
On 1965-66 cars, caster and camber are controlled by shims between the frame bracket and the upper suspension arm pivot shaft. Caster is adjusted by removing shims from the front bolt and placing them at the rear bolt, or vice versa. Camber is varied by adding or removing the same number of shims from both front and rear bolts.
From 1967 to 1973, any caster adjustment is accomplished by lengthening or shortening the struts at the frame cross-member. In order to adjust, both nuts should be turned an equal number of turns in the same direction, and the adjustment for one side should be within 1 / 4 ° of the adjustment for the opposite side. Caster adjustment on these cars is accomplished by loosening the lower control arm pivot bolt and rotating the eccentrics.
Toe-in on all models is adjusted by loosening the clamps on the sleeves at the outer ends of the tie rod and turning the sleeves equal amounts in the opposite direction, in order that the steering wheel spoke alignment is maintained during the adjustment of toe.
See Figure 5