A brake drum is a smooth metal cylindrical housing attached to the wheel hub. It is an essential component of your car’s braking system that enables you to slow down or stop. Most new cars come with rotors at each wheel. Older cars may have drums at the rear wheels instead of rotors. It is the friction between brake shoes and drums that cause your car to slow down and stop. As the drums wear out, they are unable to dissipate the heat caused by the braking system. This will cause the brake fluid to boil and weaken its ability to slow and stop the car.