Automotive Q & A

Knowledge Database - Brakes

Question: Drum Brakes - How do they Work

Answer: Drum brakes are responsible for stopping your vehicle. Drum brakes are usually located on rear wheels because of the need for a parking brake. Parking brakes are added much easier to a drum brake than to a disc brake. Drum brakes contain several different parts: brake shoes, which are used to press against the brake drum and create the necessary friction to stop your vehicle; a backing plate, which basically holds everything together and is attached to the axle; brake drum, which is attached to the wheel; wheel or brake cylinder, which contains the pistons; return springs; and a self-adjusting system that will adjust the position of the brake pad when the brake isn’t applied. When the brakes are applied, brake fluid forces the pistons to push against the brake shoes, which press against the drum, which will stop the wheel and vehicle. Then, when the brake is released, the return springs send the brake shoes back to their original position. Brake shoes are located very close to the drum so that when you step on your brake pedal, the brakes are immediately applied. Over time, the surface of the brake shoes wears and the position of the shoes must be adjusted so it doesn’t have to travel a farther distance to come into contact with the drum. If the drum brakes didn’t have a self-adjusting system, you would have to press down farther and harder on your brake pedal before the brakes would be applied.

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