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 camber is the amount the top of the wheels incline in or out from the vertical.
Front axle caster is the amount in degrees that the top of 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.
Wheel toe-in is the distance by which the wheels are closer together at the front than the rear.
These points should be checked at regular intervals, particularly when (or if) the front axle has been subjected to a heavy impact. When checking wheel alignment, it is important that the wheel bearings and knuckle bearings be in proper adjustment. Loose bearings will affect instrument readings when checking the camber and toe-in.
If you start to notice abnormal tire wear patterns and handling characteristics (steering wheel is hard to return to the straight-ahead position after negotiating a turn), then front end misalignment can be suspected. However, toe-in alignment maladjustment, rather than cast or camber, is more likely to be the cause of excessive or uneven tire wear on vehicles with twin I-beam front axles. Seldom is it necessary to correct caster or camber. Hard steering wheel return after turning a corner is, however, a characteristic of improper caster angle. Nevertheless, the toe-in alignment should be checked before the caster and camber angles after making the following checks:
- Check the air pressure in all the tires. Make sure that the pressures agree with those specified for the tires and vehicle model being checked.
- Raise the front of the vehicle off the ground. Grasp each front tire at the front and rear, and push the wheel inward and outward. If any free-play is noticed between the brake drum and the brake backing plate, adjust the wheel bearings.
There is supposed to be a very, very small amount of free-play present where the wheel bearings are concerned. Replace the bearings if they are worn or damaged.
- Check all steering linkage for wear or improper adjustment. Adjust and/or replace all worn parts.
- Check the torque on the steering gear mounting bolts and tighten as necessary.
- Rotate each front wheel slowly, and observe the amount of lateral or side run-out. If the wheel run-out exceeds 1 / 8 in. (3mm), replace the wheel or install the wheel on the rear.
- Inspect the radius arms to be sure that they are not bent or damaged. Inspect the bushings at the radius arm-to-axle attachment and radius arm-to-frame attachment points for wear or looseness. Repair or replace parts as required.
See Figure 1
The caster angles are designed into the front axle and cannot be adjusted.Camber
See Figure 2
The camber angles are designed into the front axle and cannot be adjusted.Toe-In
See Figure 3
Toe-in can be measured by using either a front end alignment machine or as follows. With the front wheels in the straight-ahead position, measure the distance between the extreme front and the extreme rear of the front wheels. In other words, measure the distance across the undercarriage of the vehicle between the two front edges and the two rear edges of the two front wheels. Both of these measurements (front and rear of the two wheels) must be taken at an equal distance from the floor and at the approximate centerline of the spindle. The difference between these two distances is the amount that the wheels toe-in or toe-out. The wheels should be always adjusted to toe-in according to specifications.
- Loosen the clamp bolts at each end of the left tie rod, seen from the front of the vehicle. Rotate the connecting rod tube until the correct toe-in is obtained, then tighten the clamp bolts.
- Recheck the toe-in to make sure that no changes occurred when the bolts were tightened.
The clamps should be positioned3/16in. (5mm) from the end of the rod with the clamp bolts in a vertical position in front of the tube, with the nut down.