Brakes - Rotor Surface Refinish
88cad04Bulletin No.: T-88-137
File in Group: 5
Number: 26
Corp. Ref. No.: 815005
Date: May '88
SUBJECT: DISC BRAKE ROTOR SURFACE REFINISH
MODELS AFFECTED: 1985-1988 DE VILLES AND FLEETWOODS 1986-1988 ELDORADOS AND SEVILLES 1987-1988 ALLANTES 1982-1988 CIMARRONS 1985-1988 RWD FLEETWOODS AND BROUGHAMS
Rotor refinish should only be required because of non-parallelism, runout, or deep scoring in excess of .015". Routine replacement of disc brake linings does not require rotor refinish.
If refinishing is necessary, the brake rotor requires a surface finish like the new vehicle rotor specifications (10 to 50 micro-inches with non-directional swirl pattern).
The recommended brake lathe settings for obtaining this finish are as follows:
Rough Cut Finish Cut
Spindle speed 150 rpm 150 rpm
Depth of cut .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, the following are important:
^ The brake lathe must be in good working order and have capability to produce the intended surface finish.
^ Excessive spindle speed, depth of cut, or cross feed can result in a rough finish.
^ Cutting tools must be sharp and changed at regular intervals.
^ Adapters must be clean and free of nicks.
^ The surface of the rotor contacting the lathe adapter must be cleaned of debris or coarse surface corrosion.
^ Lathe finish cuts, which do not produce the required finish, must be further improved and made non-directional by dressing the rotor surface with a sanding disc power tool (AMMCO Model 8350 Safe Swirl Disc Rotor Grinder or AMMCO Model 8750 Swirl Grinder or equivalent).
To become familiar with the required surface finish, drag the fingernail over the surface of a new rotor from parts stock or one on a new vehicle. If your brake equipment cannot produce this finish when correctly used, contact the equipment manufacturer for corrective instructions.
When installing new rotors from service stock do not refinish the surface as these parts are to recommended finish. It also is not required to refinish a rotor on a vehicle which has a smooth finish.