More from: storage tanks

Truck Air Brakes and Jake Brake: Not the Same Thing

Our role as a leading provider of truck tarps, cargo control equipment, trailer parts and other trucking supplies gives us the opportunity to speak to a lot of people within the trucking industry. It also gives us the opportunity to explain some of the finer points of how trucks work. For example, we sometimes have to explain that a truck air brake and Jake brake are not the same thing. What confuses people is the fact that the Jake brake releases compressed air when activated.

It’s true that both truck air brakes and Jake brake are related to compressed air in terms of function. But that’s the only similarity. The standard air brake is the truck’s equivalent to the hydraulic brakes on a standard passenger car. The Jake brake is not really a break at all. It is a mechanism that helps slow down a truck by manipulating how the diesel engine fires. Both kinds of brakes are explained below.


Truck Air Brake System

A typical truck air brake system utilizes a combination of storage tanks, pumps, and valves to pressurize and depressurize the system. When the tank is empty, the system is depressurized. This results in brakes being fully deployed. In order to release the brakes, the storage canister must be filled with air. This is what we call recharging. The need for recharging explains why truckers have to let air tanks fill up before they can engage first gear and drive away.

Inside the cab, deploying the brakes works the same way as it does in a standard passenger vehicle. The driver simply depresses the brake pedal to stop the vehicle. What’s different is this: instead of forcing hydraulic fluid into the brakes, depressing the brake pedal releases air from the storage tank, thereby moving a piston that forces the brakes to engage. Releasing the brake pedal allows the system to recharge itself, releasing the brakes.

Jake Brake

A Jake brake is a compression release engine brake attached to a diesel engine. Activating the brake opens exhaust valves on the engine to release some of the compressed air inside. This slows the vehicle by slowing down combustion. The Jake brake can slow an idling vehicle substantially.

To understand this better, think of your own passenger vehicle. Even when you take your foot off the accelerator, power is still being transferred from your engine to your transmission and wheels. The only way to interrupt that power is to either shift the car into neutral or shut off the engine. The same is true for big trucks.

The Jake brake slows the truck by reducing the amount of power transferred to the wheels. It allows the truck to slow even when it is still in gear, which is why you might sometimes hear the loud noise caused by a Jake brake as a truck rolls through a lower speed zone. Rather than disengage the gear and apply the standard air brake, a driver may simply choose to take his/her foot off the accelerator and temporarily activate the Jake brake.

The main downside to the Jake brake is that it can make a tremendous amount of noise when deployed. For that reason, some municipalities have limited the use of Jake brakes within their jurisdictions.

As for the standard truck air brake system, it also makes a unique sound. Deploying air brakes tends to make a whooshing sound followed by a hard squeaking. Neither of these noises is terribly loud as long as the system is functioning properly.

The 3 Most Important Parts of an Air Brake System

The air brake system on a tractor-trailer is a complex system that includes storage tanks, a compressor, valves, hoses, and two different kinds of braking systems: service brakes and emergency brakes. Everything working together ensures that a truck is able to stop safely under any conditions. Yet it only takes one failure to create a serious problem.

If ten truck drivers were to be asked the question, ” what the most important component in a brake system?” chances are there would be ten different answers. From our perspective, however, there are three critical components that make or break every system out there:


1. Air Brake Coils

Those coiled hoses you see spanning the distance between tractor and trailer are known as truck air brake coils. Actually, two of them (one blue and one red) are hoses that work the air brake system on the trailer. The other is a cable that supplies the trailer with electric service.

Truck air brake coils are a critical link between tractor and trailer. If the two hoses and one electrical cable do not functioning properly, a dangerous situation could arise. For example, a driver could be trying to stop without using the trailer brakes, increasing the chances of a dangerous jackknife. Alternatively, a malfunctioning trailer system could deploy by itself while the truck is in motion. This could result in loss of control.

It is critical that truck drivers maintain their air brake coils in top condition. These should always be inspected prior to each journey to ensure they are in good working condition.

2. Emergency Brake System

The emergency brake system does two things. First, it allows the parking brake to be deployed if needed. Second, it maintains a small amount of pressurized air in reserve to stop the truck just in case there is a leak in the service brake system. Emergency brakes exist in both tractors and trailers.

We include emergency brakes in our top three most important components because they provide redundancy. The last thing a truck driver needs is to attempt to stop his/her vehicle, discover he/she has an air leak, and not be able to keep the vehicle under control in order to avoid an accident. Emergency brake systems are designed to give the truck driver that needed control.

3. Air Compressors

Third on our list are the air compressors that make everything work. You can have truck air brake coils and emergency brake systems in perfect working order that could suddenly become useless if compressors fail. Compressors are to air brake systems what fluid reservoirs are to hydraulic brakes.

Unlike hydraulic fluid reservoirs, pressurized air tanks do not maintain a constant level of air on their own. In a hydraulic system, fluid is forced back and forth as the brake pedal is pressed and released. It is a closed system that maintains a constant level of fluid as long as there are no leaks. Air brakes are not a closed system.

When a driver steps on the brake pedal, pressurized air is released from the storage tank then moves through the hoses and into the brake system where it activates a piston that activates the brakes and linings. But releasing the brake pedal does not force the air back in the opposite direction. Instead, air is simply released. It is the job of the compressors to recharge the tanks before the brakes are needed again.

Every part of an air brake system is important, but these three components are at the top of our list. What would be on your list?