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How Do Air Brakes Work? All You Need to Know

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Understanding “how do air brakes work?” helps mechanics diagnose and troubleshoot any braking system issues. In general, the air braking system works very similarly to the hydraulic system. The only difference is that you rely on computerized air instead of hydraulic forces generated by the braking fluids.

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Did you know that larger tractor-trailers and diesel trucks don't have the typical hydraulic brakes in our small cars? Yes! They have a specific type of brakes that relies on air instead of fluid. Strange right?

Automotive experts and vehicle manufacturers realized that the larger trucks and trailers require specific designs to help drivers control the vehicle and prevent safety issues on the road. Therefore, they decided to use an air-powered braking system that doesn't have problems related to brake fluid leaks.

Diesel truck drivers and mechanics need to understand how to do air brakes work so they can diagnose and troubleshoot an internal issue to resolve the problems fast without complications.

This article provides all details you need to know about “how do air brakes work?” Furthermore, and since many of us are not familiar with air brakes, the article will answer some of the common and frequently asked questions related to the idea of the air braking system.

How do air brakes work?

To help you best understand “how do air brakes work?” First, think about it the air brakes concept is a similar concept to the hydraulic brakes. In other words, the entire idea of an air braking system relies on using compressed air and instead of hydraulic fluid that you rely on to stop your vehicle using a hydraulic brake.

A vehicle equipped with an air braking system consists of important components, including the compressor, which is a component connected to the engine and is responsible for pumping the pressurized air into specific air tanks. Pressurized air stays in these tanks until it's needed and whenever you want to engage the air brakes.

Right after you apply the service brakes, your vehicle immediately or at least has the parking brakes. It is important to note that while the service brakes rely on that pressurized air, the parking brakes rely on a specific spring force. This way, when your vehicle runs low on-air pressure, you don't have to worry about stopping the vehicle because you can immediately rely on the parking brakes that overpowers the low air pressure using the spring forces.

In most trucks and larger vehicles, you will come across either a drum brake, disc brake, or probably sometimes a combination of both types of brakes. Let's take a closer look at the different types of air brakes and how each one specifically works:

1.    Drum brakes

If you drive a vehicle equipped with a drum brake, the braking process goes this way:

  • The braking system is activated immediately after you press on the brake pedal
  • Once the braking system is activated, air travels from the air tanks to the brake valves
  • The brake valves then send the pressurized air to the brake chambers that pushes on a specific slack adjuster
  • The slack adjuster forces the cams to rotate using a rotational power
  • Once the camera rotates, it forces the rulers to go up and slows down the drum using the pressure of the shoes
  • Once you remove your foot from the brake pedal, all air goes back to the exhaust, and the shoe goes away from the drum to keep it from slowing down.

2.    Disc brakes

On the other hand, if you're driving a vehicle equipped with a disc air brake, the process gets slightly different, but it starts the same way:

  • You activate the braking system by pressing on the brake pedal
  • Like the drum brakes, the air is then released from the air tanks and sent to the brake valves
  • Once the air reaches the valves, it is then sent to the chambers that it’s a specific caliper. Once the caliper is activated, it slides on the inner pads until it gets to the brake rotor
  • As the calipers moving, another bridge moves with it on the outer portion against the rotor
  • With all these forces in place, the pads force the wheels to stop by squeezing against the rotor
  • Once you release your foot from the brakes, the process is reversed, and the vehicle continues driving.


Since the air braking system might be new to many of us, we must understand and highlight some of the very common FAQs that we receive continuously. Therefore, let's take a closer look at the following questions to help you better understand the concept of air braking systems.

1.    Are air brakes reliable?

Yes, air brakes are very reliable, and they are great options for larger vehicles, as we indicated earlier. However, the biggest advantage of air brakes is that you don't have to worry about fluid leaks because the air brakes are very effective even though if you're dealing with measure links.

This benefit is extremely useful and important for drivers who drive larger trucks and trailers because stopping the truck is extremely necessary, especially when you're delivering larger loads on public roads where a lot of people are driving around you.

The other benefit is that you don't have to worry about the fluid supply when driving a car equipped with an air braking system because these vehicles have an unlimited air supply. On the other hand, driving a car with a hydraulic braking system relies on a specific amount of brake fluid, which means running out of fluid.

2.    Is it hard to use air brakes?

According to automotive experts, it can be challenging to control a vehicle equipped with air brakes. You will notice that stopping the car will not be as smooth as stopping another vehicle equipped to have a hydraulic braking system.

The main reason for this behavior is that air is compressible, which means that when you press on the brake pedal, you don't expect the same amount of force to each and apply the braking force. Instead, a good portion of the force that you apply gets lost through compressing the air among the air pathways.

That's why it's critical that you understand “how do air brakes work?” to be able to expect whether it's harder or easier to stop an air-brake vehicle.

3.    Are air brakes better than hydraulic brakes?

In general, air brakes are considered more reliable and better than hydraulic brakes in stopping the vehicle and dealing with leaks. If you're driving a car equipped with a hydraulic system, any minor or Major League results in a complete failure. However, if you are driving a vehicle equipped with an air brake system, you don't have to worry about these leaks because the braking system still is effective.

On the other hand, as we indicated before, it can be challenging to control a vehicle equipped with an air braking system because air is compressible. Therefore, deciding whether the air brakes are better than hydraulic brakes depends on your own goals and priorities.

4.    Do air brakes cool quickly?

No, air brakes take a much longer time to cool down as compared to hydraulic brakes. This is because air doesn't flow as fast as water or hydraulic fluids. That's why mechanical faith is one of the very common issues with driving a car equipped with an air braking system. This happens when the brakes get extremely hot. It gets challenging to stop the brakes unless you hit the pedal with more force, especially if your vehicle has a drum air braking system.

5.    What happens when air brakes fail?

When the air brakes fail or have an internal problem, you will immediately notice a low air pressure alarm on your vehicle’s dashboard. This indicates that there is not enough pressure in the air pathways which means that you won't stop the car.

However, all these larger cars and airplanes or buses are equipped with an emergency braking system used as a backup. As we indicated before, this emergency system does not rely on the air brakes and instead, it uses a spring force to get the vehicle to stop when needed.

6.    Why do air brakes take longer to stop?

If you drove two vehicles, one equipped with an air braking system and the other equipped with a hydraulic system, you'll notice the difference between how long it takes to start the car. Typically, a vehicle equipped with a hydraulic braking system will stop much faster than the other one.

This is because the braking fluids flow much faster, and once you hit the brake pedal immediately, your vehicle will stop very fast. On the other hand, it takes longer for the air to flow through the air pathways and reach the specific components to stop the car on time.

The other thing is the very common mechanical fade that most air braking system vehicles deal with. This happens when you continuously hit the brake pedal to stop the car, especially driving in traffic.

When that happens, the brake system itself gets very hot, and once it reaches a specific point, it won't take much longer for you, and you'll need to apply a much bigger force to stop the vehicle, especially if you're driving cars with a drum air braking system. This should not be a problem if you're driving a car equipped with a disc air braking system.

7.    What are the common Air brakes problems?

Air brakes provide your vehicle with many benefits, but this doesn't mean that they are problems free. In other words, you will still deal with some big problems that might cost you thousands of dollars to get repaired. Here are the common types of air brakes problems that you might encounter during the lifetime of your vehicle:

  • Slow air pressure Which makes the brakes ineffective at some point
  • Too many air leaks reduce the required amount of pressure to get your vehicle to stop when needed
  • Water or oil making its way to the air reservoir impacts the performance of the air brakes and might get your vehicle into safety issues

8.    Are air brakes more expensive than hydraulic brakes?

Yes, according to automotive experts, expect to pay an extra $2500 at least to upgrade or use an air braking system compared to the hydraulic braking system. This is because the air braking system consists of extra, more expensive components than a simple hydraulic system.

Final thoughts

They are braking systems necessary for any larger diesel vehicle. This system is not very complicated, and it's not that big of a difference from the typical hydraulic braking system. The only difference is that the air braking system relies on air as the mean fluid to send the hydraulic power instead of fluid.

This article highlighted exactly how the air braking system works because understanding “how do air brakes work?” helps mechanics better diagnose any braking system-related problem in diesel vehicles which then helps them resolve the issue fast.

If your vehicle has a problem with the air braking system, you must take it over immediately because it has to do with your safety and the people around you. However, if your car has other mechanical problems, it might not be worth the time and investment to resolve these problems because it might cost you a lot of money. So instead, you're advised to sell your vehicle and use its value to purchase a better car with no major problems.

Cash Cars Buyer is willing to remove your vehicle within one to three days only! Cash Cars Buyer is one of the top-rated car removal companies in the nation that guarantees to pay you the top dollars and provide you with free towing despite your living location around the United States.

Our process is very straightforward and doesn't take more than a couple of days to get your car removed safely and for the most money.

All it takes you is to:

  • Describe your car’s type and condition
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  • Accept the quote
  • Get your car removed and receive your cash payment on the spot!

To learn more about our process and our teen, you can reach out to us by giving us a call at 866-924-4608 or visit our home page click on the free instant online offer.

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