Drum Brake System: Description and Operation

The rear drum brake assembly is a leading/trailing design. When the brakes are applied, the wheel cylinder pistons move both shoes out in order to contact the drum. The shoes contact the drum using enough energy in order to perform the following actions:
^ Overcome the rotation of the wheels
^ Slow the vehicle
^ Stop the vehicle (with continued application).

Adjustment for both the primary and secondary shoes is automatic when the brakes are applied.

Normally, the primary shoe will wear at a faster rate than the secondary shoe. Reinstall the brake shoes in the same position from which the shoes were removed. Do not switch the position of shoes that have been in service. This may render the self-adjustment feature inoperative and result in increased pedal travel.