How Do Boat Trailer Brakes Work?

Posted on: 20 May 2015


You may have noticed that your boat trailer is only connected to your towing vehicle by the coupler. This observation may have led you to wonder how the trailer brakes when you are towing it. If you're driving your boat trailer for the first time, learn more how the braking system works for a smoother experience.

Hydraulic Surge Brakes Defined

Most boat trailers use the hydraulic surge brake system in their operation. This system relies on detecting the difference in inertia between the towing vehicle (such as your SUV) and the trailer. Inertia refers to the reluctance of the tow car, and trailer to start moving (if it was stationary) or to stop moving (if it was already in motion). That difference in inertia generates a braking force that slows down, or brings your boat trailer to a complete halt. This prevents the trailer from "barging" into the tow car.

How the Surge Brakes Work

As the tow car moves, it creates momentum that pulls the boat trailer until both are moving at the same speed. When you approach an intersection and you slow down, the tow vehicle has a lower inertia than the boat trailer. This is because the tow vehicle has slowed down while the trailer is moving at a higher speed (at least for a few moments).

The difference in the inertia of the tow vehicle and the inertia of the boat trailer creates a force, which is exerted on a push rod found inside the coupler used to attach the trailer to your car. That push rod transfers that force onto the brake pads within the drum on the wheels of the boat trailer. The brake pads constrict and prevent the wheels from rotating at the same pace as they were rotating, thereby slowing down the movement of the boat trailer.

When you again accelerate the tow vehicle, the force exerted on the push rod is removed so the brake pads release the wheels to move again. That is how the boat trailer can again move at the same pace as the tow vehicle. This push-release sequence will be repeated the next time you brake, or accelerate. That means the more you break, the more the push rod will act upon the brake pads. In other words, there is a direct relationship between how hard you brake the tow car and how much force the push rod exerts on the brake pads.

As you can see, there are mechanisms to synchronise the movement of your tow vehicle and the boat trailer. Thus, there is no risk that your car will be damaged by the trailer when you brake. Learn more or get new parts through resources like Transtyle Trailers.