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What is a Brake Axle?

By Lori Kilchermann
Updated May 17, 2024
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A brake axle is found on a trailer. It contains a braking system that is typically magnetic or electric. This allows the trailer to apply its own brakes when assisting the tow vehicle in bringing the trailer to a controlled stop. This type of braking system is also activated by a wire, which engages the trailer brakes in the event the trailer becomes unhooked from the tow vehicle.

When pulling a trailer without a brake axle, the trailer can become difficult to control under emergency braking conditions. The trailer will sway and will often jackknife if the tow vehicle is forced to fully engage its brakes. The brake axle will apply braking to the trailer in such instances and often prevent the wild and erratic movement of the trailer.

On trailers with more than one axle, the brake axle will be placed in the froward axle in most instances. This is due to the loaded trailer having the greatest percentage of weight on the forward-most axle. A brake axle placed in the rear could cause the tire to skid under duress braking conditions, rendering the brakes useless. Higher-end trailers may have all axles equipped with brakes.

On an electric brake-equipped trailer, the tow vehicle must have a brake activation switch wired into its braking system. This switch will usually be installed under the dash of the tow vehicle and will have lights to signal when the trailer brakes are being applied. This switch will also have a manual override lever that allows the operator to apply the trailer brakes independently of the tow vehicle's braking system.

One added benefit of a brake axle on a trailer is its ability to apply the brakes and stop the trailer in the event of it coming loose from the tow vehicle. A wire, hooked between the trailer and the tow vehicle, will pull the brakes on should the trailer come loose from the tow hitch. This will stop the trailer and prevent it from rolling uncontrolled a great distance down the road.

Brake axle maintenance is relatively easy with only minimal parts involved. A good visual inspection and seasonal wheel bearing greasing is typically all that is required to keep the brake axle in good condition. An occasional application of the trailer braking system is encouraged to keep all of the parts in top operational condition. With the trailer empty, apply the brakes suddenly and check to ensure the trailer brakes engage.

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Discussion Comments

By TreeMan — On Aug 11, 2011

@Izzy78 - I have never seen a manual override switch in any normal sized trucks. Once you start getting into bigger models like the 3/4 ton pickups, you will start to see them. At least the ones I have seen, the switch is more of a sliding gauge so that you can control exactly how much force you want to apply to the brakes. Otherwise the trailer might stop in its tracks if full pressure is always applied.

As far as maximum towing capacity goes, you should never exceed whatever the truck is rated to tow and the trailer is rated to carry. Anything above these numbers could lead to the towing combination becoming extremely unstable, especially if you are going downhill. If you got in an accident as a result of not following all of the towing instructions, you would probably be held responsible.

By Izzy78 — On Aug 10, 2011

I am confused about the manual override. I have driven a lot of trucks before, but I have never seen anything like a manual override switch for pulling a trailer. I have never heard of being able to control the brakes on a trailer, either. Admittedly, I have only pulled small trailers before.

Is this something that is only necessary for really big trailers, or is the override switch just a special feature that can be added on to different truck models? If you do have a truck with a manual override, does it increase the maximum towing capacity of the vehicle since you then have more control over the trailer?

By kentuckycat — On Aug 10, 2011

I have never driven a truck with a large trailer before, but I think I may have to during an upcoming move. The article talks about having a brake activation switch. Is this only available with the electronic braking system, or is it just required for electronic and optional for magnetic?

If you have a trailer with magnetic brakes, will you still know for sure when the brakes are being applied? Also, is there any other way that you would manually control the magnetic brakes?

Finally, if you did have a truck towing a trailer with electronic brakes, when would you need to use the manual override? Is it only if the trailer starts to get out of control like when going down a hill, or is it normal to have to use it regularly when you are driving?

By titans62 — On Aug 09, 2011

I knew that a lot of larger trailers had their own brakes, but I never knew about the emergency wire that turns the brakes on when the trailer is disconnected.

If the trailer came unhooked from the towing vehicle, how long would it normally take for it to stop on its own? Also, I am familiar with normal car braking systems, but how does the magnetic or electric braking system work? I would guess the magnetic system works a lot like the rotor from disc brakes, but without as much contact. I'm not sure about the electric, though. Can someone help me out?

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