Drum Brake - function

Drum Brake

For the drum brakes to function correctly, the brake shoes must remain close to the drum without touching it. If they get too far away from the drum, the piston will require more fluid to travel that distance, and your brake pedal will sink closer to the floor when you apply the brakes. This is why most drum brakes have an automatic adjuster.

The emergency brake on a car has to be actuated by a different power source than the primary braking system. The drum brake design allows for a simple cable actuation mechanism.