Check the thickness variation by measuring the rotor thickness at four or more points around the circumference of the rotor. Use a micrometer calibrated in ten-thousands of an inch. Make all measurements the same distance in from the edge of the rotor.

A rotor in the front disc brakes 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. The C3500HD Models must not exceed 0.025 (0.001 in), as well. Replace or refinish to specifications any rotor that exceeds the designated thickness variation range.