Louis Renault (1877-1944) is a well-known name in motoring, and in 1902 the French engineer invented the drum brake for cars.
Drum brakes work in a similar way to bicycle brakes, using friction to slow and eventually stop a fast moving wheel. In cars, the friction is caused by pads that press against the inside surface of the rotating drum that is connected to the car wheel. The pads provide a wedging action that stops the wheel spinning and thereby stops the car moving.
To function correctly, the brake pads need to linger close to the drum without scraping it during normal driving. If the pads are too far away—for example, when the pads wear down from use—then the brake pedal has to be pressed deeper to get a braking action. To avoid this, most drum brakes have an automatic adjuster that regulates the distance between the pads and drum. Even though drum brakes were very successful in cars for many years, in the 1960s they began to be replaced in some car models by disk brakes.
The first drum brakes were mechanically operated but later used oil pressure pistons. Although drum brakes are still used today they have the major disadvantage of needing frequent adjusting and replacing. The force of friction on the pads wears them away fairly quickly. If a driver is heavy on the brakes then inevitably the pads will need replacing more often, which adds to the cost of upkeep. However, because drum brakes are often less costly and easier to produce than alternative brake designs, they are favored by some car manufacturers.
