Functions of Brake Shoe

Brake shoes are an integral part of the braking system of a motor vehicle. When a driver steps on the brake, the brake shoe is the mechanical part that he or she is ultimately controlling to bring the car to a stop. The backing of a brake shoe is a metal part, but the area that actually comes in contact with the brake is padded to provide friction to stop the car without damaging the brake itself. Brake shoes are found inside of drum brakes; disc brakes have calipers, which serve the same function in a slightly different way.
Drum brakes work using hydraulic pressure. When a driver steps on the brake, brake fluid under pressure travels to the individual wheel brakes, and small hydraulic pistons push the brake shoes onto the inside of the spinning surface of the wheel. The friction from the brake shoes slows the wheel down, and ultimately brings it to a halt. When the break is released, springs pull the brake shoe back into a resting position, clear of the wheel. Disc brakes work in the same way, except that instead of applying pressure from inside a drum, calipers grip a disc which stops the wheel. 
With time, the surface on the brake shoe will start to wear down. If allowed to wear down completely, the metal backing of the brake shoe will come into contact with the drum, potentially causing serious damage in addition to an unpleasant sound. For this reason, most drum brakes have an inspection hole so that drivers can check on their brake shoes without dismantling the wheel. When the brake shoes start to wear down, they need to be replaced for effective braking. The padded lining used to be made from asbestos, but more environmentally friendly materials are used in most modern cars.
In general, most cars have drum brakes on the rear wheels and disc brakes on the front wheels. The drum brakes also house the mechanism for the emergency brake, so it is important to make sure that they are in good working order. Make sure to check on all your brakes regularly, and replace pads and shoes when needed to save expensive refinishing or replacement bills for the discs and drums that stop your car. It is possible to replace your brake shoes yourself, if you have mechanical experience. Servicing drum brakes is harder than working on disc brakes, however, and you may want to turn to the services of a reputable professional mechanic to replace your brake shoes.