What are the five basic components of a truck air brake system?

Getting to know a trucks breaking system

If you wanted to be a professional chef, you would need to learn your way around the kitchen. You would need to have a general idea of how all the available appliances actually work. Why would professional truck drivers not be held to the same standard of knowing the way around their kitchens, those kitchens being the actual trucks they drive?

If you have aspirations of being a professional truck driver, you will need to invest some time in learning about how a big truck actually operates. Yes, the way big trucks operate is quite different than the way a standard automobile operates. That should not surprise you, considering the size of a big rig.

While big trucks have several intricate operating systems, we want to focus on one in particular. That would be the truck air brake system. Of course, the brake system is arguably the second most important system on any vehicle with the engine occupying the top spot.

In an attempt to educate you about the air brake systems it takes to stop big trucks, here are the five components with which you need to be concerned.

1. Truck Brake System No. 1 – The Air Compressor

Air is the primary source for making any hydraulic system work. It’s the job of the air compressor to make sure air brakes have the proper balance of air in the brake lines. This is of vital importance because an air brake system without the proper air pressure will fail to stop a big truck when the brakes are applied. As you can imagine, that would be a major issue if a big truck was on even the slightest decline in the road.

Big truck air compressors are run by either a gear or belt-driven system, depending on the make, model, and year. Additionally, air compressors are kept cool by open either air or an engine cooling system. All of these components can be found in the local truck shop.

2. Truck Brake System No. 2 – The Air Reservoirs

When brakes are applied on a big truck, they need to react immediately. In order for that to happen, there have to be tanks or reservoirs that are filled with air from the truck’s air compressor. The more air that is immediately available, the better and faster the brakes will react.

Air reservoirs are actually pressure-rated tanks that serve as air storage. These tanks feature special drain valves called draincocks. To ensure the brake lines stay clean, draincocks can be kept open to allow for an even and constant flow of air in and out of the reservoirs.

3. Air Brake System Part No. 3 – The Foot Valve

The foot valve or brake pedal is the driver’s connection to the truck’s brake system. When the driver presses the foot valve, the air from the compressor and reservoirs is released into the brake line, causing the soon to be mentioned brake chamber to be set in motion.

As a note of caution, slamming on the brakes of a big truck is not a good idea. It interrupts the constant flow of air through the brake line, which becomes a major issue because air compressors require time to release enough air to make brakes effective again.

4. System No. 4 – The Brake Chambers



Of course, there needs to be a process by which air is converted to a mechanical source that will make brakes work properly. That process takes place in brake chambers, also known as brake pots.

The air collects in the brake chambers where pushrods are set in motion. It is this motion that causes the brake shoes to compress against the brake drums, eventually bringing the truck to a fast and safe stop. The chambers are held in place with clamps while valves control how much air gets pushed into each brake chamber.

5. Air Brake System No. 5 – The Brake Shoes and Drums

This is where it gets back to basics in terms of how brakes work. The compressed air is released, eventually forcing the brake shoes or pads to compress against the brake drums. The friction that is caused through this process is what causes the wheels to slowly stop rotating.

Whether a truck relies on brake shoes or pads will depend on the make, model, and year of the truck. The brake shoes have a special lining that helps prevent the production of heat when the shoe hits the brake drum.

Resumé – Maintaining a Reliable Truck Air Brake System on Your Big Truck

It won’t take long for you to learn that your brakes are your best friend while you are on the road. As your best friend, you want to make sure you keep your brakes healthy at all times. To do that, you want to constantly monitor the air pressure coming from your compressor. You will also want to make sure all the above parts are periodically cleaned and replaced when necessary. Parts are available at any good truck repair shop.

Please note

This article is provided for information purposes. It does not replace the opinion of a certified truck technician from C.T. Cam & Ressorts Industriels Laval Inc.
Please always bring your heavy truck into garage for any and all service.