Brake Rotor/Disc: Description and Operation

QUALITY AND TOLERANCE
In manufacturing the brake rotor, tolerances of the braking surfaces for flatness, parallelism, and lateral runout are closely held. 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 finish must be held to a specified range a 60 degree radius of roughness or less. A new rotor falls into this surface finish range, as will a rotor that is refinished exactly as directed. Control of the braking surface finish is necessary to avoid the problems of hard pedal "application" excessive brake fade, pulls and erratic performance. In addition, control of the surface finish can improve lining life. Light scoring of the rotor surfaces not exceeding 1.5 mm (0.06 inch) in depth is not detrimental to brake operation, and may result from normal use.