Rotor Tolerance and Surface Finish

During the manufacturing of the brake rotor, tolerances of the braking surfaces for flatness, parallelism and lateral runout are held very close. The maintenance of close tolerances on the shape of the braking surfaces is necessary to prevent brake roughness or pulsation. In addition to these tolerances, the surface Amish must be held to a specified range, 50 Ra roughness or less. A new rotor falls into this surface finish range, as will a rotor which is refinished exactly as directed. Control of the braking surface finish is necessary to avoid problems of hard pedal apply, excessive brake fade, pulls and erratic performance. In addition, control of the surface finish can improve pad life. Light scoring of the rotor surfaces not exceeding a depth of 1.5 mm (0.060 inch), which may result from normal use, is not detrimental to brake operation.