I found this on the web about causes of tire wear. I hope it helps.
Shoulder wear, which can be caused by under-inflation or hard cornering. Many shredded rubber tires seen along highways are the result of either under inflated tires, running too long and too hot, or from severe misalignment.
Center tread wear, which usually indicates over-inflation. Over inflation results when a vehicle owner tries to compensate for a slow leak by over inflating the tire to make it stay up longer.
Cupping can be caused by an unbalanced tire condition, faulty wheel bearings, loose parts, fatigued springs or weak shock absorbers. Check the condition of the shock by forcefully bouncing the front end of the car several times and releasing it on the down stroke. Failure of the vehicle to settle after two strokes suggests worn shocks or struts.
Camber or toe wear indicates misalignment due to loose, worn or bent steering linkage components. Many camber and toe wear problems can be traced to spring fatigue, which causes the vehicle's frame to ride closer to the road. Once the vehicle is below the manufacturer's height specifications, it is not possible to achieve the correct camber change designed into the suspension without replacing the springs. The vehicle also experiences excessive toe change as the suspension travels through jounce and rebound, again causing abnormal tire wear.
Diagonal scuffing and cupping across the face on rear tires signals problems with toe. Diagonal tread wear or cupping on rear tires is caused when the direction the vehicle's wheels are heading is not in line with the geometric center line of the vehicle. When this condition occurs, front-wheel steering can be affected and lead to tire slip or loss of traction or control. (Note: The wear pattern that develops on rear tires from improper toe will vary depending on tread design. Wear patterns from rear-wheel misalignment may resemble cupping on tires with highway tread design and diagonal scuffing on tires with an all season tread pattern.
