Rear Disc Brakes

DESCRIPTION







Rear disc brakes are standard equipment on this vehicle.
The rear disc brake system on this vehicle is made up of the following components:
- Disc Brake Caliper
- Brake Shoes and Linings
- Brake Rotor










The rear caliper utilizes a single piston, slider-type design. The caliper is mounted with slide pins and bushings to allow the necessary lateral movement during operation. The rear caliper assembly mounts directly to the rear knuckle which is attached to the rear upper and lower control arms.







The rear calipers have a two-stage (stepped) cylinder bore. The piston is located in the large diameter part of the bore. The parking brake adjuster mechanism is located in the smaller diameter part of the bore.
The rear calipers are not serviceable and must be replaced when diagnosis indicates this is necessary.
The only serviceable components on the rear disc brakes are the brake shoes, operating lever, lever return spring and the slider pins, bushings and boots. The rear calipers are not serviceable and must be replaced if diagnosis reveals a problem.


OPERATION
The rear disc brake caliper used on this vehicle is a unique, dual function design. It serves as the normal wheel brake caliper, and also serves as the vehicle parking brake.
The rear disc brake components serve the same purpose for the rear brakes as the front disc brake components do. The parking brake feature is the difference.
The complete parking brake mechanism consists of: the caliper piston; a worm shaft; two discs (drive and driven); a disc preload spring; and an operating lever and return spring. The parking brake cables are attached to the operating levers.
The worm shaft is attached to the piston with a spring washer and lock ring. The driven disc is threaded to the worm shaft and the drive disc is seated in the caliper. The operating lever is bolted to the drive disc. The lever is connected to and operated by the parking brake rear cable. The lever return spring is attached to the lever and to a lug on the caliper body.
The drive disc rotates the spring loaded driven disc by means of ball bearings. The bearings are secured to the drive disc and seat in cam ramps machined in the driven disc.
In normal braking mode, the rear calipers operate the same as the front calipers. The brake shoes are applied by fluid pressure acting against the caliper piston and bore surfaces.
When parking brakes are applied, the park brake cables pull the park brake operating levers forward. This rotates the discs and worm shaft causing the piston to extend and apply the brakes. Since normal brake shoe operating clearance is quite small, only a modest amount of piston movement is needed for brake application. A stop bolt is used to limit the total amount of piston extension.
The parking brake mechanism is self adjusting to compensate for lining wear. As wear occurs, drive-to-driven disc clearance increases. This causes the drive disc ball bearings to move farther up the cam ramps in the driven disc increasing the amount of rotation. The extra rotation produced is enough to extend the piston for adjustment.