Brake Rotor - Servicing Procedures
Group: CHASSISNumber: 94-50-003
Date: MAY, 1994
Model: ALL
Subject:
BRAKE ROTOR SERVICING
PURPOSE:
This Technical Service Bulletin describes brake rotor servicing procedures when an on-the-car brake lathe is used to correct variations in brake rotor thickness and run-out conditions. Warranty labor operation time allowances are provided.
AFFECTED VEHICLES:
All with front or rear disc brakes
DESCRIPTION:
For optimum braking performance, all brake rotors must be carefully serviced to meet recommended thickness and run-out tolerances. It is important to check rotor run-out and thickness prior to servicing the rotors.
When turning rotors to correct uneven thickness or excessive run-out, the best results will be obtained by using an on-the-car brake lathe such as, Pro-Cut, Model VBG-610. Regardless of the brand or type of brake lathe used, follow the lathe manufacturer's instructions for properly servicing the rotors.
BRAKE ROTOR SERVICING PROCEDURES:
The following procedures apply to all vehicles with front or rear disc brakes. Refer to Group 58 of the specific vehicles shop manual for correct brake rotor thickness and run-out tolerances.
BRAKE ROTOR RUN-OUT
1. Remove the brake caliper support bolts and raise the caliper upward, away from the rotor. Secure the caliper out of the way with a wire hook.
2. Inspect the brake rotor surface for grooves, cracks, and rust. Clean the rotor of all debris before proceeding.
3. Position a dial gauge approximately 5 mm (0.2 in.) from the outer edge of the rotor, zero the gauge and measure the run-out. Refer to the appropriate service manual for allowable run-out specifications.
NOTE:
Use the wheel lug nuts to secure the rotor to the wheel hub. (Do not use an impact gun).
4. If the rotor run-out equals or exceeds allowable specifications, change the position of the rotor and hub. (Remove rotor and install on different lug bolts)
5. Re-check the rotor run-out and if necessary re-position the rotor until the minimum run-out is achieved.
6. Resurface the rotor using an on-the-car brake lathe if run-out is above specification and/or rotor has grooves deeper than 0.38 mm.
BRAKE ROTOR THICKNESS VARIATION
1. Measure thickness of the brake rotor at 8 different positions using a micrometer. Each measuring position should be 45 degrees apart and 10 mm from the outer edge of the rotor. Refer to the appropriate service manual for the allowable thickness variation specification, or use the suggested thickness variation specification of 0.010 mm.
NOTE:
The thickness variation between any two measurement positions must not exceed the allowable or suggested specification.
2. If the thickness variation is above the specification limit, and if the rotor was NOT resurfaced in the BRAKE RUN-OUT PROCEDURE, resurface the rotor using an on-the-car brake lathe.
3. If run-out and/or thickness variation measurement remains above specification after brake rotor resurface with an on-the-car brake lathe, the cause may be the brake hub or the knuckle assembly or their bearings and/or hub.
WARRANTY INFORMATION
The 8-digit operation code shown in the chart DOES NOT apply when an off the car brake lathe is used.
LABOR OPERATION TIME FOR ON THE CAR BRAKE ROTOR MACHINING OF FRONT OR REAR BRAKES
BRAKE ROTOR SERVICING PROCEDURE FLOW CHART