Why Do Trucks Have Air Brakes? (Find Out Why!)

Last Updated on December 27, 2022 by Leepu Da Maxim

Nowadays, most trucks have air brakes because air brakes have many key advantages over hydraulic brakes. Air breaks offer more braking force than hydraulic brakes which makes it easier to stop heavier vehicles. Another important advantage of air breaks is that they are very easy to main and maintenance costs are also very low.

Key Takeaways

  • The air brake system is based on the air so this braking system won’t run out of operating fluid
  • Air brakes are less prone to failure than hydraulic brakes which makes them the safest option
  • Air brakes are less affected by temperature changes so you will have a smooth and similar performance from this type of brake
  • Air brakes do not suffer from the wear and tear of mechanical components such as brake pads and rotors

Advantages and Disadvantages of Air Breaks

How Do Air Brakes Work?

1. The air brake system has an unlimited supply so that no moment is left unused.  
2. The procedure for coupling the airlines requires less effort and time to connect  
3. Air is also used to store potential energy while compressing the air  
4. The level of efficiency is not lost even in the presence of some leaks in the system
1. An air brake system requires a larger budget  
2. Repair and maintenance costs in the first five years are higher than other brake systems  
3. They are more difficult to operate than other options

4. Specialist knowledge is required to check the proper functioning of an air brake system
How Do Air Brakes Work

In principle, we should mention that air brakes are normally used on buses or trucks, as these are heavy vehicles. In this case, it is a complex system that is made up of different parts or components. Thus, the main parts are the air storage tank, the control pedal, the parking brakes, and the service brakes.

Therefore, because a set of different parts is included, it isn’t easy to use the braking system. In principle, we should mention that the parking brake has a drum or disc as its main part. This in turn is combined with a spring pressure to keep the vehicle in the same applied position.

So, a certain amount of air pressure is needed to efficiently release the parking brakes that have been used. On the other hand, it is sometimes necessary to apply the service brakes. In particular, these brakes are often used while the vehicle is being driven.

Here, the driver must use these brakes to slow the truck or vehicle or even come to a complete stop. Here the driver simply has to press the brake pedal with the necessary force. By doing this it is possible to direct the air under a certain level of pressure to the right parts. Here, the air pressure is approximately 6.89 – 8.27 bar, or 690 – 830 kPa, or 100-120 psi.

In particular, this air under pressure is directed exactly into the brake chamber resulting in the exact activation of the brake. It is also possible to find in the vast majority of trucks that the air brake used is a drum brake. However, in some industries and geographical areas disc brakes are beginning to be used more and more in large vehicles.

Besides, all drivers of heavy vehicles have a certain meter at the time of driving. Simply put, this gauge provides information about the available air pressure for safe functionality at that time. Here, in turn, it is possible to find different indicator light designs and tones to provide the best information.

At What PSI Are The Air Brakes Locked?

At What PSI Are The Air Brakes Locked

Here, the amount of air pressure needed to lock the air brakes is 60 psi. Beyond that, this particular value may vary depending on the type of vehicle a person is required to drive. Some large vehicles such as buses have several warning devices.

In this case, when the air pressure is approximately 80 to 85 psi, the warning devices report low pressure. This is important because with inadequate pressure in the air brake system, then functionality will not be adequate. This could be dangerous, as it is not easy to stop a vehicle with a significant weight load.

What Happens If You Apply The Air Brake While Driving?

Here, it is important to consider that when an air brake is applied while the person is driving, then the spring brakes are activated. In particular, this happens when only one air brake is activated.

So, when you press the necessary buttons, then the air is sent directly into the brake chamber. So as mentioned above this manages to compress the springs necessary for the air brake to activate.

Beyond that, it is not recommended to suddenly activate the air brake in a big vehicle. When a person does this suddenly, control of the vehicle may be lost at a certain level.

How Long Should It Take To Build Up Air Pressure?

In this case, the accumulation of enough air for braking may vary depending on the type of vehicle involved. For one thing, it takes approximately 45 seconds, or perhaps less, to build up air pressure of 85-100 psi. So this may be more than enough for efficient and precise braking.

It’s also important to consider this aspect because a large vehicle, such as a bus or truck, may not have the pressure necessary for efficient braking. When this happens, warning indicators about low pressure are usually included.

How Do You Unlock The Frozen Air Brakes?

In some parts of the world, temperatures can be too low and this can impair the functionality of a vehicle. So, sometimes air brakes freeze and don’t work properly. To fix this problem, you should tap the top and bottom of the drum.

Once you have done this you must move the truck back and forth several times. Alternatively, air pressure can be used to break up the ice that has formed inside the system. To do this, you must repeatedly cut off and re-establish the air supply. Therefore, this procedure should be enough to cut off your air brakes again.

Related Article: The Best Way To Bleed Your Car Brakes

Why Should Air Tanks Be Drained?

As we have already mentioned, some climatic conditions in many cities of the world can deteriorate or damage the functionality of a vehicle. That is why it is necessary to take certain precautions, especially in places where temperatures are too low. At the same time, it is also important to drain the air tanks in these situations.

In particular, compressor oil and water could easily enter the tank. When this happens, cities with too cold temperatures can easily freeze oil and water. In turn, when this happens then brake failure increases greatly. So to avoid these simple problems you will need to drain the air tanks.