How Drum Brakes Work

Figure 1. Location of drum brakes.

Drum brakes work on the same principle as disc brakes: Shoes press against a spinning surface. 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 HowStuffWorks, we will learn exactly how a drum brake system works, examine the emergency brake setup and find out what kind of servicing drum brakes need.

How Drum Brakes Work

Figure 2. Drum brake with drum in place

How Drum Brakes Work

Figure 3. Drum brake without drum in place

Let's start with the basics.