GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

DRUM BRAKES

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CAUTION
Older brake pads or shoes may contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning the brake surfaces, use a commercially available brake cleaning fluid.

The drum brake assembly used on these vehicles is an advanced leading/trailing shoe design. It operates with fewer parts, yet is equivalent to other drum brakes in performance while providing improved reliability.

In this assembly, a single universal spring holds both shoe and lining assemblies to the backing plate, and acts as a retractor spring for the shoe and lining assemblies.

When the brakes are applied, the wheel cylinder moves both shoes out to contact the drum. With forward wheel rotation, the leading (forward) brake shoe will wrap into the drum and become self-energized.

With reverse wheel rotation, the trailing (rear) brake shoe will wrap into the drum and become self-energized.

Force from the brake shoes is transferred through the fixed anchor and backing plate to the axle flange. Adjustment is automatic and occurs on any service brake application.

With leading/trailing brakes, the leading shoe wears at a faster rate than the trailing shoe. DO NOT switch the position of the shoes that have been in service as this may render the self-adjustment feature inoperative, resulting in increased pedal travel.

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the drum brake components

 
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