Brake Rotor Measuring

In manufacturing 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 and brake noise.

In addition to these tolerances, the surface finish must be held to a specified range. The control of the braking surface finish is necessary to avoid pulls and erratic performance and to extend lining life.
When performing routine brake maintenance, rotors should not be refinished, unless there is a brake pulsation caused by the rotors or the rotors are excessively scored.

Scoring of the rotor surfaces not exceeding 1.5 mm (0.060 in.) in depth, which may result from normal use, is not detrimental to brake operation.





THICKNESS VARIATION CHECK
Thickness variation can be checked by measuring the thickness of the rotor at four or more points around the circumference of the rotor. All measurements must be made at the same distance in from the edge of the rotor. Use a micrometer graduated in ten-thousandths of an inch (0.002 mm).

A rotor that varies in thickness by more than 0.013 mm (0.0005 in.) can cause pedal pulsation and/or front end vibration during brake applications. A rotor that does not meet these specifications should be refinished to specifications or replaced.