Rotor Wear or scoring can be caused by linings that are Worn through to the rivets or backing plate, or by friction material that is harsh or unkind to the mating surface. Rust, road dirt, and other contamination could also cause rotor scoring. Light scoring (less than a depth of 0.015 inch [.381 mm]) of the disc braking surface can occur during normal brake use. This does not affect brake operation; however, it can result in a higher-than-average brake shoe lining Wear rate. But, any rotor having score marks more than 0.15 inch (3.8 mm) should be refinished or replaced.