Jake Brakes: How Do They Work, and Are They Illegal?

Semi-truck parts tend to wear faster than those on passenger cars. That has a lot to do with the vehicle’s size and the fact that big rigs rack up many miles quickly. Some auto parts, such as Jake brakes, can improve a semi-truck’s lifespan. Learn more about Jake brakes, including how they work, if they’re legal, and whether they affect a truck’s engine.

What is a Jake brake?

Jake brakes are found on semi-trucks
Kenworth semi-truck | Kenworth

Jake brakes are designed to save wear and tear on service brakes. If used properly, they can add years to a truck’s brakes. They also save wear and tear on tires.

“Jake brake” might sound clever because it rhymes, but that’s not the reason for the term. 

“The name ‘Jake brake’ comes from a product that, unsurprisingly, is named the Jacobs engine brake,” The Drive reports. “The company that makes them, Jacobs Vehicle Systems, says that its system is a diesel engine retarder that uses the engine to help slow the vehicle. It alters the engine’s exhaust valve operation so that the engine acts as a power-sapping air compressor.”

Generic names are “decompression brakes” and “engine brakes.” They work by opening the exhaust valves to an engine’s cylinders — releasing compressed gas and allowing the truck to slow.

These brakes are typically used on diesel trucks, not passenger cars. Generally, the only other vehicles with these parts are large enough that standard brakes aren’t enough to stop them efficiently.

Are Jake brakes illegal?

The answer to whether Jake brakes are illegal depends on the area. Many municipalities are OK with using engine brakes, while others ban them.

That’s primarily because of the noise they make, Matheson explains. Jacob brakes are fantastic for saving wear and tear on a truck’s service brakes, but they’re also incredibly loud when going downhill. So some places have outlawed them.

However, it’s not that big of a deal because truckers activate engine brakes with the flip of a switch, which means they aren’t always on. Plus, road signs should clarify where and when they aren’t allowed. They will say things such as “Trucks, please, no Jake brake” or “Engine brakes prohibited.”

But the real question is whether these brakes can hurt the truck’s engine.

Can a Jacob brake damage a truck’s engine?

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If you’re using a Jake brake, you might wonder whether you’re harming your truck’s engine. The answer is yes and no. Keep these points in mind to avoid damage:

Check your oil before a long trip. If the oil is low, you could hurt your rig’s engine. Using Jacob brakes increases the risk of engine damage.

It’s also crucial to let your engine warm up if you plan to use a Jake brake. On trips when time matters, it might be frustrating to wait, but it’s wiser to take a few minutes to warm up your truck before heading out. 

Finally, be aware of your engine’s RPMs when going downhill. Pushing the RPMs over the engine’s maximum limit can lead to damage.

If you take the time to follow the above steps, using Jake brakes can save wear and tear on your truck. Just be sure to check for road signs about their use. Otherwise, they’re worth the investment.