A drum brake chamber is a component of a drum brake system in a vehicle. It is a cylinder that houses a spring and a diaphragm, and is connected to the brake pedal or brake lever. When the brake pedal or lever is pressed, it pushes against the diaphragm, which in turn pushes against the brake shoes and causes them to press against the inside of the drum. The spring in the chamber helps to return the brake shoes to their original position when the brake is released. Drum brakes are typically found on the rear wheels of a vehicle, but may also be used on the front wheels in some cases.