The brake drum is a heavy flat-topped cylinder, which is usually sandwiched between the wheel rim and the drive wheel. The inside surface of the drum is acted upon by the friction material of the brake shoes. When the brakes are applied, the friction material of the brake shoes is forced into contact with the brake drums to slow the rotation of the wheels. The friction between 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 increasingly being fazed out in favor of rear disc brakes. Drum brakes were standard equipment on the front wheels of most cars until the early 70's.