For 1990-2009 cars

Check thickness variation by measuring the brake rotor thickness at 4 or more points around the circumference of the brake rotor. Use a micrometer calibrated in ten-thousands of an inch. Make all measurements about 25.4 mm (1 in) in from the edge of the brake rotor.

A brake rotor that varies in thickness by more than 0.02 mm (0.001 in) can cause brake pedal pulsation and/or front end vibration during brake applications. Refinish or replace a brake rotor that does not meet these specifications.