For 1990-2009 cars

Inspect the thickness variation by measuring the rotor thickness at 4 or more points around the circumference of the rotor. Use a micrometer that is calibrated in increments of 0.025 mm (0.001 in). Perform all measurements at the same distance in from the edge of the rotor.

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