In this system, that surface is called a drum.
Many cars have drum brakes on the rear wheels and disc brakes on the front.
Drum brakes have more parts than disc brakes and are harder to service, but they are less expensive to manufacture, and they easily incorporate an emergency brake mechanism. In this edition of How Stuff Works , the third in a six-part series on brakes, we will learn how a drum brake works. If you missed the last two articles be sure and check them out using the links below. Consecutive articles will cover the rest of the components of a car brake system, detailing how each one operates. Inc. All rights reserved.