Auto Transport Brake drum

The brake drum is very heavy flat-topped cylinder that is usually sandwiched between the wheel rim and the drive wheel. The inside exterior of the drum is acted upon by the friction fabric of the brake shoes. When the brakes are functional, the friction material of the brake shoes is forced into contact with the brake drums to measure the rotation of the wheels. The friction connecting the tires and the road surface then slows the car's speed. Drum brakes are found on the rear wheels of most cars, but they are ever more being phased out in favor of rear disc brakes. Drum brakes were normal equipment on the front wheels of most cars until the early 70's.