Disc Brake Rotor Machining

NOTE: Whenever the brake rotor has been separated from the wheel bearing flange, clean any rust or foreign material from the mating surface of the rotor and flange. Failure to do this may result in increased lateral runout of the rotor and brake pulsation.

Do not refinish brake rotors when performing routine brake maintenance, such as replacing worn disc brake pads.Do not refinish brake rotors to correct any of the following conditions:

Brake noise, such as a growl or squeal
Premature brake lining wear
Superficial corrosion of the rotor braking surface
Rotor discoloration

Refinish a rotor only under the following circumstances:

There is a complaint of brake pulsation caused by: Lateral runout in excess of specification, brake rotor thickness variation in excess of specification; corrosion or pitting that is deeper than the rotor braking surface.
There is scoring greater than 0.060 in. (1.5 mm).

All of the brake rotors have a minimum thickness dimension cast into them. This dimension is a minimum wear dimension, not a refinishing dimension. Do not use a brake rotor that, after refinishing, will not meet the specifications shown on the rotor. Use a new rotor.

Accurate control of the rotor tolerance is necessary for proper performance of the disc brakes. Use only precision equipment in order to machine the rotor. Service the machining equipment on a regular basis. Follow the manufacturer's recommended maintenance procedure.

The following tool accessories must be in good condition when refinishing rotors:

Attaching adapters
Tool holders
Vibration dampeners
Tool bits

Always use sharp cutting tools and bits. Use only replacement cutting bits recommended by the equipment manufacturer. Dull or worn tools leave a poor surface finish which will affect braking performance. Always use vibration dampening attachments when refinishing braking surfaces. The attachments eliminate tool chatter and will result in a better surface finish. Ensure that the adapters are clean and free of nicks.

After machining the rotor, use 120-grit aluminum oxide sandpaper and, if available, a non-directional rotor finisher in order to create a non-directional braking surface. Clean the braking surfaces with GM P/N 12377981, or with an equivalent brake parts cleaner.

NOTE: For best results, use an on-vehicle brake lathe whenever you are refinishing a rotor in order to correct a problem with brake pulsation. Follow the equipment manufacturer's recommended specifications and procedure.