GM Service Manual Online
For 1990-2009 cars only

Brake Rotor Thickness Variation Check for Oldsmobile Eighty Eight 1998

Check thickness variation by measuring the rotor thickness at four or more points around the rotor's circumference. Use a micrometer calibrated in ten-thousandths of an inch, and make all measurements at the same distance in from the edge of the rotor.

A rotor which varies in thickness by more than 0.025 mm (0.001 inch) can cause pedal pulsation and/or front end vibration during braking, and thus should be refinished to specifications, or replaced.