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Brakes are one of the fundamental components of any motor vehicle. Air brakes are the type of brake most commonly used by commercial motor vehicles (CMV) like tractor-trailers, trucks. To ensure the air brakes on your semi-truck operate safely, you must first understand how they function.


Air brakes use compressed air. This system provides an unlimited air supply and eliminates fluid leaks in CMVs, keeping truckers safe while transporting tens of thousands of pounds of freight.


In an air brake system, an engine-mounted compressor pressurizes the air. The compressor pumps the pressurized air into tanks that store it until needed. When a driver presses the brake pedal, the air travels through a chamber and triggers a mechanism to apply pressure to the brake drum. This mechanism slows the vehicle to a stop.


Air brake systems also use air pressure to actively hold back large springs that enable an emergency brake. These brakes will engage automatically if the system loses pressure due to an air leak. so read on to learn how air brakes work in your CMV.


To help you better understand its function, we broke up the system into its components.

AIR COMPRESSOR: The air compressor is the main component of an air brake system.

 STORAGE TANK: The storage tank stores compressed air at high pressure.

BRAKE PEDAL: The brake pedal is the mechanical linkage that initiates the brake application, operated by drivers inside the commercial vehicle.

 BRAKE ACTUATOR: The brake actuator is a piston-cylinder mechanism connected directly to the brake pedal. When a driver presses the pedal, this mechanism creates pressure.

BRAKE DRUM: The brake drum is mounted on the vehicle’s tires and performs the braking action.

BRAKING LINES: Braking lines, also known as supply lines, transfer compressed air from the storage tank to the brake drum.

TRIPLE VALVE: The triple valve has three primary applications: charging air into the storage tank, applying pressure to the brakes when the braking line pressure drops, and releasing the pressure from the brakes after the stop is complete.

 DIRT COLLECTOR: The dirt collector is a small device used to collect dirt particles that the air filters separate.

 SAFETY VALUE: The safety valve attaches to the storage tank to prevent it from bursting. The valve releases some air when the pressure reaches a certain value.



The first step toward a rewarding trucking career is earning your commercial driver’s license (CDL)