6. Rear Drum BrakesFig. 6-1, on the next page, is an exploded view of the rear drum brake assembly. Retaining springs hold the brake shoes in place. The shoes rest against a fixed bracket at the bottom of the backing plate. When the brakes are applied, the wheel cylinder pushes against the tops of the shoes to force them against the brake drum. Return springs retract the brake shoes when the brakes are released. The rear brakes are equipped with a self-adjusting mechanism which compensates for wear. At the top of the backing plate, the brake shoes rest against the slotted adjusting bar. As the brake lining wears and brake shoe travel increases, the spring-loaded adjusting wedge fills the gap between the brake shoe and the adjusting bar, essentially lengthening the adjusting bar and keeping the brake shoes from retracting too far from the drum. Because the rear brakes do less of the work of stopping the car, they are not likely to wear as quickly or require service as frequently as the front brakes. Unless problem symptoms are actually observed at the rear brakes, troubleshooting of brake problems should always include the front brakes. If the rear brakes are worn and require service, then at the very least the front brakes should also be thoroughly inspected. The brake shoes, the drums, and the attaching and adjusting parts are subjected to the greatest wear, and are the components most often needing attention. The brake shoes are designed to be routinely replaced as they wear out. While it is possible to restore the brakes by replacing only the brake shoes, full braking performance and minimum lining wear can only be achieved if the drums are resurfaced or replaced at the same time. Removal of the brake drums requires cleaning, repacking, and adjusting the wheel bearings during reassembly, as described in SUSPENSION AND STEERING.
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