How do Trailer Brakes Work?

You know the brakes on your trailer are very important and need to be well maintained and checked often for wear and tear, but have you ever wondered how they work? Unlike the brakes on your tow vehicle, trailer brakes are designed specifically to insure maximum safety and thus operate differently than the brakes in a car or truck.

Trailer brakes are available in three different systems: hydraulic, electric, and electric over hydraulic (EOH). Depending on where and how you tow your trailer will influence which brakes are best for you. Hydraulic trailer brakes use a surge actuator/coupler. When your tow vehicle stops, the surge actuator releases fluid into the brake which triggers the mechanism in the brake itself to activate. Hydraulic surge brakes are an entirely self-contained system and need no hookups to the towing vehicle. However, there is a split second delay between wherein the trailer load pushes the tow vehicle and activate the surge actuator. This does require a longer distance to stop your rig so make sure to be wary of this while driving.

Electric brakes immediately call up a lot of questions because of the concern of electricity and water. They are not used for boat trailers because of this and are primarily for utility trailers. However, electric over hydraulic (EOH), is a combination of the two. They contain an electrical brake component and a hydraulic component which work in tandem to allow heavy duty boat trailers to stop safely and without damaging the braking system. The electrical part is in the front (ie. standard coupler, emergency brake kit, in cab electric brake controller). You purchase an EOH controller which acts as the brake coupler. The driver can control the output of the electric brakes and the signal goes into the EOH controller that converts that into a hydraulic output that sends the brake fluid back to the calipers or drums. This is typically used on heavy duty boat trailers (30-42 feet) as well as for drivers that going over hills or through the mountains. EOH are preferable in these scenarios because when you are going down hills with the standard hydraulic brakes, the coupler compresses which activates the brakes and will cause the brakes to burn up. With the EOH there is no coupler so the brakes will not activate until the brake pedal is pressed.


One thought on “How do Trailer Brakes Work?

  1. I’ve always wondered how trailer brakes work. It makes sense that they would need to be connected to the car that’s towing them! That way the car can power the brakes.

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