A drum brake is a part of a braking system in which the friction is caused by a set of shoes or pads that are pressed against the inner surface of a rotating drum when pressure is applied on to the brake pedal. The drum in the brake system is connected to the rotating wheel. Most of the cars have drum brakes on the rear wheels and disc brakes on the front. While considering drum brakes, one important factor to remember is that drum brakes have more mechanical parts than disc brakes which are harder to service. But the drum brakes are less expensive to manufacture, and they easily fit into an emergency brake mechanism.

A typical drum brake system consists of hydraulic wheel cylinders, brake shoes and a brake drum. The working mechanism of the disc brake is quite simple compared to the disc brakes and operates when the brake pedal is applied to the two curved brake shoes. These brake shoes have a friction material lining and are forced by hydraulic wheel cylinders against the inner surface of a rotating brake drum. The result of this contact generates high friction which in turn enables the vehicle to slow down or stop. The drum brake is the most common braking system that is found in most of the cars only to be replaced by more reliable disc brake systems.