Brake disc — inspection, removal and installation
Warning: The dust created by the brake system is harmful to your health. An approved filtering mask should be worn when working on the brakes. Never blow the brake dust away with compressed air. Do not, under any circumstances, use petroleum-based solvents to clean brake parts. Use brake system cleaner only!
Inspection
1. Loosen the wheel lug nuts, raise the vehicle and support it securely on jack stands. Remove the wheel.
2. Remove the brake caliper. It isn’t necessary to disconnect the brake hose. After removing the caliper bolts, suspend the caliper out of the way with a piece of wire (see illustration).
6.2 Hang the caliper out of the way with a piece of wire — don’t let it hang by the brake hose!
3. Visually check the disc surface for score marks, cracks and other damage. Light scratches and shallow grooves are normal after use and may not always be detrimental to brake operation. Deep score marks or cracks may require disc refinishing by an automotive machine shop, or disc replacement (see illustration). Be sure to check both sides of the disc. If the brake pedal pulsates during brake application, suspect disc runout.
4. Drive test the vehicle and listen for any grinding or unusual mechanical noises from the brake system. If any noises are noticed perform a visual inspection. The most common symptoms of out of round discs is a pulsation felt in the steering wheel as light pressure is applied to the brakes. Check the disc for runout with a dial indicator. See this Chapter’s Specifications (see illustration).
6.4 The brake pads on this vehicle were obviously neglected, as they wore down completely and cut deep grooves into the disc — wear this severe means the disc must be replaced
5. To check disc runout, place a dial indicator at a point about 1/2-inch from the outer edge of the disc (see illustration). Set the indicator to zero and turn the disc. Indicator readings should not exceed the specifications (see this Chapter’s Specifications). If the disc is out of round and is still within the specified thickness the disc will require refinishing by an automotive machine shop or disc replacement. If disc refinishing or replacement is not necessary, you can deglaze the disc surface with emery cloth or sandpaper (see illustration).
6.5a To check disc runout, mount a dial indicator as shown and rotate the disc
6.5b Using a swirling motion, remove the glaze from the disc with sandpaper or emery cloth
6. It’s absolutely critical that the disc not be machined to a thickness under the specified minimum thickness. The minimum wear (or discard) thickness is cast into the underside of front discs (see illustration) and on the outside of rear discs. The disc thickness can be checked with a micrometer (see illustration).
6.6a the minimum thickness is cast into the disc (typical)
6.6b Use a micrometer to measure disc thickness
Removal
7. Remove the two caliper mounting bracket bolts and detach the mounting bracket (see illustrations).
6.7a Caliper mounting bracket bolts – front
6.7b Caliper mounting bracket bolts – rear
All except rear discs on models with dual rear wheels
8. On heavy-duty models with RPO J96, unscrew the hub extension retaining nuts and detach the hub extension.
9. If pressed-metal retaining clips are present on any of the wheel studs, cut them off (see illustration).
6.9 Cut off and discard the disc retaining washers , if present (it isn’t necessary to reinstall them)
Note: It is not necessary to reinstall these pressed-metal retaining clips. (The clips are installed at the factory only to hold the disc in place until the caliper is installed later on down the assembly line.)
Rear discs on models with dual rear wheels
10. Remove the rear hub and bearing assembly (see Driveline).
11. Unscrew the bolts from the back side of the hub assembly and separate the disc from the hub.
Installation
12. Clean the disc and hub mating surfaces with a wire brush.
13. On all except rear discs on dual rear wheel models, place the disc in position over the threaded studs.
14. On models with dual rear wheels, place the disc onto the hub, aligning the match mark (if installing the same disc). Apply non-hardening thread locking compound to the threads of the bolts and install them, tightening them to the torque listed in this Chapter’s Specifications. Install the hub and disc assembly (see Driveline).
15. On models with RPO J96, install the hub extension and tighten the nuts to the torque listed in this Chapter’s Specifications.
16. Install the mounting bracket and tighten the bolts to the torque listed in this Chapter’s Specifications. Install the brake pads.
17. Install the caliper onto the mounting bracket, tightening the bolts to the torque listed in this Chapter’s Specifications.
18. Install the wheel and lug nuts. Lower the vehicle and tighten the lug nuts to the torque listed in the Tune-up and routine maintenance Specifications. Depress the brake pedal a few times to bring the brake pads into contact with the disc. Bleeding won’t be necessary unless the brake hose was disconnected from the caliper. Confirm that the brakes are fully operational before resuming normal driving.