Drum brakes are a type of automotive brake commonly used by almost all car manufacturers. They work to stop a moving vehicle when the driver applies pressure to the brake pedal, which pushes fluid through the hydraulic lines leading to the drum brakes. Typically, drum brakes are installed on the rear wheels of a car, with higher performing disc brakes in the front of the vehicle, as the front of the car provides a much higher percentage of the stopping power. Because brakes are integral to vehicle safety, all of the brakes on a vehicle should be checked on a regular basis to ensure that they are functioning well.
The system of automotive brakes working from inside a drum has been around since the early 1900s, although drum brakes have been extensively refined since then. The basic design, however, remains much the same. A partially closed drum or cylinder is attached to the wheel, with brake shoes inside the drum. When the driver brakes, the shoes come into contact with the drum, forcing the car to stop. Brake pads made from highly heat tolerant materials on the inside of the brake shoes increase friction and prevent metal to metal contact while the driver is braking.
Disc brakes, on the front of a vehicle, work along similar principles, although the brake shoes take the form of calipers which grip a spinning disc. Disc brakes are considered to be superior to drum brakes, which is why they are mounted on the front of a car. However, disc brakes are also more expensive. The diminished stopping power of drum brakes is perfectly suitable for most driving situations, so most car manufacturers combine the two braking systems to bring the initial and maintenance costs of the car down. Only high performance cars need a four wheel disc braking system.
The secondary use of drum brakes is as an parking or emergency brake. The simple mechanical system used to operate drum brakes can be set up to work even without hydraulic pressure, and in many cars the emergency brake system links directly to the rear drum brakes, rather than to a separate brake. In cars which have four wheel disc brake systems, additional drum brakes are installed on the rear wheels for emergency situations.
If the brake pads on drum brakes become worn down, the brakes will lose efficiency and eventually cease to work. Because of this, it is important to check on the brakes regularly to ensure that they are in good working order. Most car manufacturers install a small viewing hole in the brake drum so that drivers can check on their brake pads without removing the entire wheel. However, the wheels should be periodically removed to perform a full inspection of the brake mechanism, and while the wheels are off, the tires can be rotated and other routine maintenance can be performed.