Tolerances on rotor thickness, parallelism, runout, flatness, and depth of scoring are very critical and must be measured with exacting gauges and micrometers. Accurate measuring tools and up-to-date rotor resurfacing equipment are required for brake rotor service. The rotors should be inspected whenever brake pads are required and when the wheels are removed for other types of service. The following are typical disc brake rotor conditions that need careful inspection.