DISC BRAKE SURFACE REFINISH - SEMI-METALLIC BRAKE LININGS

MODELS AFFECTED: ALL MODELS EQUIPPED WITH DISC BRAKES

To meet mandated brake system performance requirements, semi-metallic brake linings have been used for several years in some vehicle applications. In order to maintain the proper performance, it is important to correctly service these semi-metallic brake systems as follows:

SERVICE RECOMMENDATIONS:

Semi-metallic linings should be replaced with semi-metallic service linings.

Routine replacement of disc brake linings does not require rotor refinish.

Rotor refinish should only be required because of non-parallelism, runout, or deep scoring.

If refinishing is necessary, the semi-metallic brakes lining requires a micro-inch surface refinish like the new vehicle rotor specification (10 to 50 micro-inches with non-directional swirl pattern).

The recommended procedure for obtaining this finish is as follows:

Rough Cut Finish Cut --------- ---------- Spindle Speed 150 RPM 150 RPM Depth of Cut Per Side .005" .002" Tool Cross Feed Per Rev. .006" -.010" .002" Max. Vibration Dampener Yes Yes Swirl Pattern-120 GRIT No Yes

When refinishing brake rotors for semi-metallic linings, the following is important:

The brake lathe must be in good working order and have capability to produce the intended surface finish.

Use correct tool feed and arbor speeds. Too fast a speed or too deep a cut can result in a rough finish.

Cutting tools must be sharp.

Adapters must be clean and free of nicks.

Lathe finish cuts should be further improved and made non-directional by dressing rotor surface with a sanding disc power tool (AMMCO Model 8350 Safe Swirl Disc Rotor Grinder or equivalent).

Rotor surfaces are to be refinished to 10 to 50 micro-inches.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.