Jake Brakes – What they do and Why Truckers Love Them

With my name being Jake, naturally I need to write this article about Jake brakes! Although, when I am talking about jake brakes I do not mean MY brakes. I am referring to the braking system that is common on large diesel trucks, and when the vehicle is slowing down it makes a distinctive shuttering noise like the car is snoring.

Truckers like jake brakes because they are effective at slowing down large diesel trucks pulling heavy loads. If the trucks were to rely solely on the conventional brake pads, they would overheat when traveling downhill on steep roads.

Truckers also get a laugh out of creating an unnecessary disturbance in quiet neighborhoods as they cruise by in early hours of the morning. With straight pipes, the blast that comes from jake brakes engaged is loud enough to wake up a small city. Satisfying the truckers’ need to feel like justice is served.

The safety aspect probably plays a bigger role, but we know the truckers must be having fun with them too.

Diesel Trucks with Jake Brakes on the road

What is a jake brake?

Jake brake is the short name for Jacob’s engine brake. The Jacob’s engine brake is a “compression release” brake equipped on large diesel trucks. When engaged, the jake brake allows compressed air from the engine cylinders to be released rather than combusted creating pressure against the rotation of the engine.

Releases compressed air from the cylinder absorbing the power of the engine slowing the vehicle.

A jake brake allows the engine to skip the power cycle of the 4 cycles: intake, compression, power, and exhaust.

The jake brake is useful for slowing the vehicle down somewhat. It is most often used by truckers on downhill slopes to avoid using the brakes at the wheels as much and is a lifesaving very necessary feature on many trucks.

Schematic of jake brake/engine brake operation

Why Truckers Like Jake Brakes

Truck drivers must certainly play games with jake brakes. The sound they make can be tremendously loud and you can bet that any time a truck is using the jake brake if they are not rolling down a steep slope, they are more than likely exacting revenge on someone in the world they have been wronged by.

Truckers ALSO like jake brakes because they reduce wear on the brake pads at the wheels as well as provide a safe, reliable, and efficient method of slowing down a very heavy truck moving quickly downhill. Jake brakes are a trucker’s lifesaver.

The air compressed in the cylinder Pushes back against the cylinder as it comes up instead of igniting and becoming the power that normally forces the cylinder down to propel the car.

Using a jake brake reduces cost significantly. There is no significant wear on the engine from using a jake brake and saves the conventional brake pads from getting worn out which can be VERY expensive due to their size.

Disadvantages of a Jake Brake

Jake Brakes are noisy! This is the biggest and ONLY disadvantage of jake brakes. If it weren’t for the noise, truckers would certainly use the jake brake more often and perhaps we would see it in more applications.

The noise level is the same reason why we do not have jake brakes on cars. The noise is simply too obnoxious to justify an alternative braking method that just isn’t necessary on small vehicles.

It IS necessary on big trucks and for that reason we want them on trucks – to keep out truck drivers safe. And those around them too.

The only other disadvantage to jake brakes is the extra parts required on the valvetrain. Of course extra parts increases the complexity of the engine and increases maintenance cost. But only slightly and not significantly enough to outweigh the cost savings on brake pads.

Advantages of a Jake Brake

This brings us to the advantages of a jake brake.

First, Jake brakes keep the crazy runaway overloaded downhill trucks with no brakes from becoming runaway trucks with no brakes!

Jake brakes are a proven, effective, reliable, safe method for slowing a vehicle.

Think of it like shifting your car into a lower gear while rolling downhill. A jake brake has a similar effect on the truck and prevents the driver from needing to engage the brakes so often.

Second, jake brakes are able to be engaged in different settings. In a low, medium, or high configuration. The driver can select how much of an effect it has on the vehicle which can be a huge advantage because of the degree of braking should be different depending on the degree of the downhill slope.

Essentially the driver is able to select how many cylinders are in “compression release” mode.

Third – the expense. Jake brakes save on the large expense on trucks of brake pads and shoes. Brake shoes and pads are very expensive on trucks because of the size of them.

And you can imagine if on your little car you have to replace your brake pads after driving it for a year or so stopping the little load in the car, how frequent truck drivers have to replace their brake pads. What a hassle!

Reduced wear on the brake pads provides a significant cost reduction.

Is a jake brake bad for the engine?

A major benefit of the jake brake is that it is not bad for the engine or harmful in any way. The design of the jake brake is such that it does not put extra strain on the engine in any way that it is not made to handle. There is no more pressure on the engine than the extreme amounts of pressure that result from diesel combustion.

That is the fourth benefit of the jake brake. Just wanted to include it down here to answer this common question!

Jake Brakes on Cars

Why Don’t We Have Jake Brakes on our cars?

The noise of jake brakes is why we do not have them on our cars! They are so dang loud it is simply not practical.

They are also generally only equipped on diesel trucks because diesels usually have much higher compression engines than gasoline engines. The larger compression provides a greater impact from the jake brake.

The biggest disadvantage of a jake brake is noise. The noise level is why we do not have jake brakes on cars.

Can you put a jake brake on a car?

The added weight and expense of a jake brake system on your car is not worth the reduction of your speed. Only large diesel engines are easily equipped with a jake brake. There is no simple kit to add a jake brake to a gasoline engine.

Where are jake brakes illegal?

Is Jake Braking Legal

Jake Braking is legal unless specified by the city or state. In some cities, jake brakes are not legal to use and the trucks are permitted to drive through but the drivers are not allowed to use the jake brake. Some cities have passed laws against the use of jake brakes due to the noise disturbance they can cause.

Trucker Engine Braking Sign

Jake Brakes are illegal in some cities where neighborhoods are close to the highways trucks drive on. There are always signs indicating that jake brakes are prohibited and there are often large fines if the law is ignored. Some states have statutes specifically addressing brake retarder use:

California, Colorada, Montana, and Oregon. Some states such as Kansas and Oklahoma, and Pennsylvania prohibit the use or engine-retarder brakes in certain circumstances.

The Connecticut General Assembly has an old research report on Jake Brakes that includes helpful information to guide you in your search for specific legislature on wherever you are concerned about driving a truck with jake brakes.

Of course the trucks that are equipped with jake brakes are permitted everywhere, and it is only the use of jake brakes that has been deemed a nuissance and illegal. The only reason that jake brakes are illegal anywhere is for the noise.

Also Asked Questions

Are Jake Brakes the Same as Air Brakes?

Jake brakes are not the same as air brakes. Air brakes are similar to conventional brakes that instead of operating with compressed brake fluid, use compressed air to engage and disengage. When you step on the brake with air brakes, air is released from a tank and the brakes are engaged.

Are there different settings for the jake brake?

Jake brakes have progressive settings. The operator can select for the jake brake to operate with 2, 4, or 6 cylinders of the engine.

What engages the jake brake?

A jake brake is engaged with a simple electrical switch on the dashboard. The electrical switch indicates 2, 4, or 6 cylinders to operate with. The switch engages a solenoid that allows oil to pass that eventually opens the exhaust valves allowing compressed cylinder air to escape.

The best place I can direct you if you need more help with this subject is to the Jacob Vehicle Systems site and their installation manual for a Jacob’s Engine Brake System

Are jake brakes the same as exhaust brakes?

Jake brakes are different from exhaust brakes. A jake brake redirects air from the engine cylinder. An exhaust brake builds pressure in the exhaust by blocking the exhaust manifold providing increased pressure back toward the cylinder.

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