People often buy tires and don't bother to think about them again until a mechanic tells them there's a problem. You can increase the life of your tire by following recommended tire maintenance schedules to decrease premature or uneven wear. One of the common ways a tire can wear is "cupping," also known as "feathering." This is wear across one side of the tread (outside or inside edge) that forms a wave and creates a loud rumbling when the tires rotate. It can cause vibrations and unsafe handling. A tire will cup for many reasons, and you can check the tires to prevent damage.
Park the vehicle on a flat, paved surface. Turn the steering wheel all the way to the left and turn the vehicle off.
Inspect the surface of each tire to ensure there are no areas with exposed steel belt. A steel belt on the surface of a tire tread can cut your hand, causing serious injury. If steel belt is showing, do not conduct the test; replace the tire immediately.
Put on the gloves and rub your hands over the flat surfaces of each tire tread. Run your hands in both directions and on the inside and outside of the edge of the tread and check for a resistance of bumps across the surface of the tread.
Move the car forward or backward (straightening the steering wheel and then turning it all the way to the left) to inspect the full circumference of each tire. A broken belt in a tire can create a waving or cupping, but may be present only in one concentrated area.
Move the vehicle forward and backward to expose a small area of the rear tires until you've checked the entire circumference. Rear tire treads are harder to see because you cannot point them outward with the steering wheel.
If you notice uneven wear cupping, have your front-end and front and rear suspension components checked by a qualified mechanic. If they check out, have your alignment checked. Comply with recommended rotation schedules. Two-wheel and front-wheel-drive tires should be rotated at least every 9,000 miles. Four-wheel and all-wheel drive vehicles should be rotated at least every 6,000 miles.