Hydraulic brakes use a liquid (hydraulic fluid) to transfer pressure from the brake pedal to the brake shoe to stop the vehicle. Air brakes have several advantages for large multitrailer vehicles: The supply of air is unlimited, so the brake system can never run out of its operating fluid, as hydraulic brakes can.
What is the function of an air brake chamber?
A service brake chamber contains a flexible rubber disc called a diaphragm, a metal rod called a pushrod and a return spring. When you press the brake pedal, compressed air fills the service brake chamber, causing the diaphragm to move and push out the pushrod to apply the brakes.