Caster and camber cannot be set or measured accurately without professional equipment. Toe-in can be adjusted with some degree of success without any special equipment.
Caster is the backward or forward tilt from the vertical of the steering knuckle centerline at the top, measured in degrees. A steering knuckle centerline tilted backward at the top has positive (+) caster, while one tilted forward has negative (-) caster. Most American passenger cars have negative or zero caster to reduce steering effort. Positive caster, as on the Blazer/Jimmy and most trucks, produces greater directional stability and requires greater steering effort, since it also increases the self-centering effect at the steering wheel.Two Wheel Drive
No two wheel drive caster specifications are given, since the method for finding the recommended angle is rather complicated. It requires algebraically adding the angle of the frame at a specified point to the measured caster angle in order to obtain a corrected caster angle, measuring the distance between the bump stop bracket on the crossmember and the top of the lower control arm bumper, and checking the measurement on a chart or graph to find the recommended corrected caster angle.
Caster is adjusted by varying the numbers of shims on the bolts holding the upper control arm pivot shaft to the frame. The torque for the bolts is 70 ft. lbs.Four Wheel Drive
Caster is fixed on four wheel drive models. If it varies significantly from specifications, the most likely cause is spring settling. About the only cure is to re-arch or replace the springs. Some truck alignment shops use tapered shims between the axle and the spring to make small caster corrections.
Camber is the inward or outward tilt, measured in degrees, of the wheel at the top. A wheel tilted out at the top has positive (+) camber. A wheel tilted in has negative (-) camber. Camber has a great effect on tire wear.Two Wheel Drive
No 1969-71 models two wheel drive camber specifications are given, since the method for finding the recommended angle is rather complicated. It requires measuring the distance between the bump stop bracket on the crossmember and the top of the lower control arm bumper, and plotting the measurement on a graph to find the recommended camber angle. Specifications are given for 1972-82 models, since the earlier method is not required.
Camber is adjusted by varying equally the number of shims on the bolts holding the upper control arm pivot shaft to the frame. The torque for the bolts is 70 ft. lbs.Four Wheel Drive
Camber is fixed on four wheel drive models. If it varies significantly from specifications, suspect steering knuckle ball joint wear. Another possibility is a bent axle tube, usually caused by those thrilling jumps. Bent axle tubes can be straightened, given the proper heavy equipment. A shop that handles truck frame straightening and alignment is the most likely place.
Toe-in is the amount, measured in inches, that the centerlines of the wheels are closer together at the front than at the rear. Virtually all cars, except some with front wheel drive, are set with toe-in. Some front wheel drive cars, and some four wheel drive trucks, require toe-out to prevent excessive toe-in under power.
Some alignment specialists set toe-in to the lower specified limit on vehicles with radial tires. The reason is that radial tires have less drag, and therefore a lesser tendency to toe-out at speed. By the same reasoning, off-road tires would require the upper limit of toe-in.
Toe-in must be checked after caster and camber have been adjusted, but it can be adjusted without disturbing the other two settings. You can make this adjustment without special equipment, if you make careful measurements. The adjustment is made at the tie-rod sleeves. The wheels must be straight ahead.
- Toe-in can be determined by measuring the distance between the centers of the tire treads, front and rear. If the tread pattern of your tires makes this impossible, you can measure between the edges of the wheel rims, but make sure to move the truck forward and measure in a couple of places to avoid errors caused by bent rims or wheel runout.
- Loosen the clamp bolts on the tie-rod sleeves.
- Rotate the sleeves equally (in opposite directions) to obtain the correct measurement. If the sleeves are not adjusted equally, the steering wheel will be crooked.
If your steering wheel is already crooked, it can be straightened by turning the sleeves equally in the same direction.
- When the adjustment is complete, tighten the clamps.