Rotor Servicing: Parallelism
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 1991 Pontiac Grand Prix, 1991 Oldsmobile Cutlass Supreme, 1991 Chevrolet Lumina, 1991 Buick Regal, and 1990 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
Check thickness of rotor at 4 or more points around edge of rotor. Make all measurements the same distance from edge. If thickness varies more than specified, refinish or replace rotor.