TIRES
What: Tires, are the most visible components of a vehicle’s suspension system, and their wear patterns can be valuable clues to the condition of other suspension system components. Tire wear is a particularly good indicator of alignment problems.
How: For example, tire wear can tell you when a wheel has too much toe-in or toe-out. When either one of these conditions exist, the tire meets the road at an angle. This results in the tire dragging sideways as it rolls, and the tread wears unevenly, with a distinctive featheredge pattern. With too much toe-in, the outside edge of each tread tends to wear off while the inner edge tends to become sharp and ragged. With too much toe-out, the reverse is true. Toe wear patterns can easily be felt by passing your hand across the tread. Excessive camber angles cause tread wear on one side of the tire only. With too much positive camber, the tire will wear on the outside edge. With too much negative camber, the wear is on the inside. Again, the pattern is a distinctive one and tells you at once that an alignment is needed.
Loose or worn suspension parts can cause tire and alignment problems. Worn control arm bushings, for example, allow the tire to wobble and slip and this causes small scuffmarks in the tread. Very loose connections caused by worn bushings or, more commonly, badly worn ball joints, can result in areas of such heavy wear that they actually become depressions.
Cupping is a condition caused by the tire bouncing as it rolls. Small areas of heavy wear are created. Worn shocks can be the cause of cupping, but loose suspension parts or tire imbalance are also possible causes.
Generally, a tire out of static balance will show wear toward the center of the tread. The imbalanced weight causes the wheel to lift vertically off the surface of the road. When it lands back down on the road, the tire scuffs the road surface. This action is called wheel hop or wheel tramp.
Dynamic imbalance causes the wheel to wobble from side to side (wheel shimmy). The tire scuffs the road surface from side to side as it rolls. Wear caused by dynamic imbalance usually shows near the edges of the tread.
Once you have a thorough understanding of the basic principles involved in suspension design and the various approaches to controlling these forces, the task of setting up a system for your car or truck should not be too difficult. However, before undertaking any major changes consult a competent source of expertise. Unlike styling changes, suspension modifications can be a matter of life and death to someone you hold very dear, yourself.