Brakes - New Front Brake Calipers Available
89chevy05GMC NUMBER: 88-T-196
GROUP: 5 - Brakes
DATE: March, 1989
CORPORATE
NUMBER: 865016R
SUBJECT: NEW FRONT BRAKE CALIPERS AVAILABLE
MODELS: 1984-86 C 1,2,3, 1987-88 R 1,2,3, AND 1984-88 G 1,2,3
New front brake calipers for the models listed above are now available from GMSPO. These new calipers have smoother bore finishes. If caliper replacement is being considered to correct a braking induced directional lead (either right or left) the following inspections and procedures should be performed. Evaluation of a vehicle's brake performance is not intended to be made with the vehicle operator's hands removed from the steering wheel. Vehicles that exhibit directional bias under these conditions are not considered to exhibit brake lead. Before road testing the vehicle, perform the following services:
Preliminary Inspection
^ Inspect tires for excessive, uneven wear - replace if necessary.
^ Equalize tire pressures.
^ Equalize parking brake adjustment.
^ Adjust rear service brakes to .030" running clearance.
^ Check and, if necessary, adjust the front end alignment including toe.
^ Inspect caliper brake line bolt (# 34, page 5A8, Figure 4, 1988 Service Manual X-8832) for proper locations of orifice. The orifice should be located in the unthreaded part of the bolt. If the orifice is located in the threaded portion of the bolt, then the bolt must be replaced.
IMPORTANT: After the preceding inspections and/or adjustments have been made, the vehicle should be road tested to verify is a lead still exists. Vehicles that lead may lead either right or left when the brakes are applied.
Make all stops on a dry, level (no crown), clean roadway.
Each applicable step must be thoroughly completed to effect a lasting repair. Failure to complete the procedures exactly as written may result in an unsatisfactory repair.
Parts are currently available from GMSPO.
Parts Information
Old Caliper New Caliper
Brake System Part Number Part Number
JB1 & 3 18012308 LH 18015427 LH
18012309 RH 18015428 RH
JB5 & 6 18007947 LH 18015383 LH
18007948 RH 18015384 RH
JB7 18009753 LH 18015385 LH
18009754 RH 18015386 RH
Warranty Information
Labor Op Description Time
T7705 Preliminary Inspection 1.4 hrs
(no further action required)
Add: If necessary to align front wheels .7
T7710 Preliminary Inspection and 3.2 hrs
repair procedure "A"
(includes two road tests)
Add: If necessary to align front wheels .7 hr
To reface rotors (both) 1.5 hrs
To replace rotor (one) .4 hr
To replace rotors (both) .7 hr
Chart 1
Good contact is important between the friction surfaces of the brake system. With semi-metallic linings, it is important to have good refinished rotor surfaces. A poor finish on one rotor can result in reduced brake effectiveness. This may result in a brake lead condition if installed opposite a properly finished rotor. The original equipment new disc brake rotors have an initial surface finish of 20 to 60 microinches and aB have a non-directional swirl pattern.
Service Recommendation
Rotor refinish requires a micro-inch surface refinish equivalent to the new vehicle rotor specification.
The recommended procedure for obtaining this finish is as follows:
Rough Cut Finish Cut
Spindle Speed 200 RPM 200 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 Optional*
* Duplication of new rotor and smoother finish for best initial brake effectiveness.
When installing new rotor from service stock "do not" refinish the surface as these parts are to recommended finish. When refinishing brake rotors 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.
^ Adaptors must be clean and free of nicks.
^ Lathe finish cuts should be further improved and made non-directional by dressing rotor surface with a standing disc power tool (AMMCO Model 8350 Safe Swirl Disc Rotor Grinder or equivalent).
^ Rotor surfaces are to be refinished to 20 to 60 micro-inch.
To become familiar with the required surface finish, drag a fingernail over the surface of a new rotor from parts stock or one on a new vehicle. If your brake equipment cannot produce this smooth a finish when correctly used, contact the equipment manufacturer for corrective instructions.
FIGURE 1 - CALIPER/KNUCKLE CLEARANCES:
The clearance between the caliper and the steering knuckle upper and lower must be equal right and left. When right and left clearances have been equalized, add one upper and one lower and the total should be between 0.26-0.60 mm (0.010-0.024 inches). File knuckle to obtain the proper clearances.