Airbrakes - An Overview

An air brake or, a compressed air brake system, is a friction brake for vehicles in which pressing compressed air on a piston is used to apply the force to the brake pad needed to stop the vehicle.

Air brakes are generally used in large heavy vehicles, especially those having multiple compartments which must be linked into the brake system, such as trucks, buses, trailers and the railroad trains.

The system is made up of service brakes, parking brakes, a control pedal, and an air storage tank. For the parking brake, a disc or drum brake system designed to be held in the 'applied' position by spring pressure is placed.

Air pressure releases these "spring brake" parking brakes. For the service brakes to be applied, the brake pedal has to be pushed, so that the air creates pressure (approx 6.89-8.27 bar) to engage the brake chamber. This stops the movement of wheels.