Refinishing Brake Rotors

^ Tools Required
- J 37704 Disc Brake Lathe

Important: It is not necessary to refinish the brake rotors when replacing the brake shoe and the lining pads assemblies.

^ Refinish the brake rotors only under the following conditions:
- The brakes are pulsating.
- The brake rotor has hot spots.
- The brake rotor is scored greater than 1.5 mm (0.060 inch).
- The brake rotor is beyond specifications.
^ The brake rotors have a minimum thickness cast into them. This is the minimum wear dimension and not a refinish dimension. Replace a brake rotor that will not meet the specified dimensions after refinishing. Refer to Component Specifications. A rotor that is too thin will not have the proper heat transfer capabilities.
^ The proper performance of disc brakes requires accurate control of rotor tolerances.
^ Use only precision equipment in machining.
^ Regularly service the machine equipment, using the manufacturer's recommended procedures for maintenance.
^ When refinishing rotors, do the following:
- Make sure that all tools, adapters, holders, vibration dampeners, and tool bits are in good condition.
- Use sharp cutting tools and tool bits. Dull or worn tools leave a poor surface finish that affects initial brake performance.
- Use replacement cutting tool bits the equipment manufacturer recommends.
- Use only vibration-dampening attachments while refinishing brake surfaces. These eliminate tool chatter, thereby promoting a better finish.
- Make sure the adapters are clean and free of nicks.
^ The Ammco Brake Lathe and the Accuturn Brake Lathe (GM dealer equipment) are recommended off-vehicle brake rotor and drum lathes that achieve good results. Follow the manufacturer's recommendations and instructions for initial setup and cutting procedures when using any brake lathe.
^ Make the brake rotor surface non-directional.
- Dress the brake rotor surfaces with a sanding disc power tool using 120 grit aluminum oxide sandpaper. Use a tool such as the Ammco 8350 or 8750 Safe Swirl Brake Rotor Grinder, or the Accuturn 433179 Non-Directional Swirl Finisher.
- As an alternate method, use a sanding block with 150 grit aluminum oxide sandpaper.
- Sand each brake rotor surface using moderate pressure for at least 60 seconds.
- With the brake rotor turning at about 150 RPM, sand each brake rotor surface using moderate pressure for at least 60 seconds.
- Clean each brake rotor surface with denatured alcohol or a substitute cleaner after sanding.