Tire Tread Wear Patterns
Outside Edges: Tires that are worn on the outside edges have been underinflated. There is excessive contact with the outer edges of the tire and the road surface as the vehicle travels down the road.
Center of tire: Tires that are worn in the center have been overinflated. There is excessive contact with the center of the tire and the road surface. Always use a tire air pressure gauge when inflating tires.
One of the edges: When the tire is worn on one side but not the other, the camber angle is off either negative or positive.
Tire is cupped: When the tire is scalloped or cupped across the tread it is usually caused by bad shocks or struts. This can also be caused by out of balance tires. Jounce the front end to see if it oscillates and test drive the vehicle to see if it floats and leans excessively around corners. Tire wear can indicate a worn steering or suspension component, an over or under inflated tire, or a misaligned vehicle.
Tire is feathered: When the tire is feathered across the tread, the tie rods are worn or the vehicle needs to be aligned. The ball studs get loose in their sockets allowing the tires to toe in/out as the vehicle travels down the road. Toe in is when the fronts of the tires are closer together than the rears and toe out is when the fronts of the tires are further apart than the rears.