When doing an alignment, not all adjustments can be made on all cars due to vehicle design. In addition, it is not always necessary to adjust all angles. Doing this allows the car to roll freely in a straight line without dragging the tires across the pavement and causing uneven tire wear. When correctly adjusted, there is no inward or outward tilt of the tire beyond the manufactures specifications. This allows more of the tire to contact the road, promoting proper handling, maximizing traction, and reducing tire wear.
Caster refers to the position of the wheels in relationship to the frame of the car.
Properly setting caster ensures the proper steering and handling that your car was designed to deliver. The rear wheels are NOT referenced. This means that adjustments are only made on the front wheels and no adjustments are made to the rear. The vehicles that require this type of alignment use a single adjusting sleeve for setting the total toe angle. The steering wheel may not adjust to be centered.