Brakes

Originally, most systems for stopping vehicles were mechanically actuated drum brakes with internally expanding shoes; i.e., foot pressure exerted on the brake pedal was carried directly to semicircular brake shoes by a system of flexible cables. Mechanical brakes, however, were difficult to keep adjusted so that equal braking force was applied at each wheel; and, as vehicle weights and speeds increased, more and more effort on the brake pedal was demanded of the driver.

Brakes are perhaps the most important safety feature of any vehicle. Knowing the different types of brakes, both between and within vehicles, can help you feel better informed when caring for and repairing your brakes.

There are two kinds of service brakes, or the brakes that stop your vehicle while driving: disc and drum brakes. Additionally, almost all vehicles come with emergency brakes and anti-lock brakes.

Disc brakes consist of a brake rotor which is attached directly to the wheel. Hydraulic pressure from the master cylinder causes a caliper (which holds the brake pads just outside the rotor) to squeeze the brake pads on either side of the rotor. The friction between the pads and the rotor causes the vehicle to slow and stop.

Drum brakes consist of a brake drum attached to the inside of the wheel. When the brake pedal contracts, hydraulic pressure presses two brake shoes against the brake drum. This creates friction and causes the vehicle to slow and stop.

Emergency brakes, also known as parking brakes, are a secondary braking system that work independent of the service brakes. While there are many different kinds of emergency brakes (a stick lever between the driver and passenger, a third pedal, a push button or handle near the steering column, etc.), almost all emergency brakes powered by cables which mechanically apply pressure to the wheels.

Anti-lock braking systems (ABS) are found on most newer vehicles. If the stationary brakes are applied suddenly, ABS prevents the wheels from locking up in order to keep the tires from skidding. This feature is especially useful when driving on wet and slippery roads.