The do-it-yourself mechanic should not attempt to perform any wheel alignment procedures. Expensive, highly-specialized alignment tools are needed and making these adjustments blindly would most likely result in damage. The 4-wheel alignment should be performed by a certified alignment technician using the proper alignment tools. The following is informational only; procedures are not outlined.
Camber is an important alignment angle because it is both a tire wear angle and a directional control angle. Camber is the inward or outward tilt of the top of the tires when viewed from the front of the vehicle. If the center line of the tire is perfectly vertical, the tire is said to have zero (O) camber. If the top of the tire tilts outward, the tire has positive camber; if the top of the tire tilts inward, the tire has negative camber. Tire wear will logically follow these tilt angles. For instance, excessive negative camber will result in wear to the inner portion of the tread.
Another problem with inaccurate camber is that the vehicle will pull to the side with the most positive camber. The effect is similar to leaning to make a turn on a bicycle.
Camber is measured in degrees and the specification is determined by the R & D team according to the physical traits and properties of the vehicle. Adjustment is accomplished at the top of the strut tower where the plate bolts to the tower. `Pushing' the top of the strut out will increase the camber, and `pulling' it in will decrease the camber.
Caster is the forward or rearward tilting of the steering axis (the center line is an imaginary line that passes through the upper mount and lower ball joint) from the vertical, as viewed from the side of the vehicle. Rearward tilt is positive caster, and forward tilt is negative caster. Zero (0) caster would indicate that the upper strut mount is directly above the lower ball joint.
Caster influences directional control, but is not a tire wearing angle. Caster also affects directional stability and steering effort. Caster angle is calculated to deliver the most desirable steering effort, normal wheel returning forces, and wheel pulling sensitivity. A vehicle will pull toward the side with the least amount of camber. Because of their naturally straight running characteristics, front wheel drive vehicle are not overly sensitive to caster, and accordingly, many (like these cars) do not have provisions for very much caster adjustment.
THRUST ANGLE AND TOE
Although the front wheels aim or steer the vehicle, the rear wheels actually control the tracking of the vehicle. Trust angle, then, is defined as the path that the rear wheels will take. Ideally, the thrust angle should be geometrically aligned with the body centerline. With front wheel drive vehicles, imperfections due to hitting the curb, running over potholes, etc. affect the thrust angle and may cause driving problems. Fortunately, adjustments are available to remedy the problem.
Toe-in is the turning in of the front wheels, as viewed from over the front of the vehicle. The purpose of accurate toe is to keep the wheels running parallel to each other. Excessive toe-in or-out will `scrub' the tire surfaces across the road surface and will cause feathered tire wear and may affect fuel mileage. Ideally, all 4 wheels will be set to manufacturer's specifications to give you the optimum ride quality the vehicle has to offer. Front toe is adjusted by loosening the tie rod jam nuts and turning the ends to push or pull the back of the knuckles out or in.