For 1990-2009 cars

Measure the rotor thickness at four or more points around the circumference of the rotor in order to inspect the thickness variation. Use a micrometer calibrated in ten-thousandths of an inch. Inspect each measurement at the same distance from the edge of the rotor.

A rotor that varies in thickness by more than 0.013 mm (0.0005 in) may cause pedal pulsation or front end vibration during brake applications. Refinish or replace a rotor that does not meet the above specifications.