Friday, February 3, 2023


Adjusting trailer brake controllers

By Russ and Tiña De Maris
A regular reader sent in this question: “I have a question about brake controllers and travel trailers. How do you adjust them? How do you know if they are too tight or not adjusted correctly?” These are great questions, and we can offer some suggestions.

Brake controller theory

First, a little on brake controller theory. Travel trailers and fifth wheels are typically equipped with electric brakes. When you step on the brake in the tow vehicle, electric current is sent from the tow vehicle back to the trailer. This current runs through an electromagnet, which forces the trailer brake pads to press onto the trailer’s brake drums. The friction between the brake pads and the drums slows the vehicle – and converts kinetic energy (for our purposes, the energy moving the trailer) into heat.

The job of the brake controller is to send the appropriate amount of current flow back to the brakes. You could send a full jolt of electricity back to the brakes, and they’d respond by jamming the brake pads into the drums, locking up the brakes. That’s converting that kinetic energy into heat way too fast – skidding the tires, making vehicle control difficult or impossible, and wearing out the brakes in a hurry.

What happens when the brake controller isn’t set properly

Set properly, the brake controller also pairs up the tow vehicle and the trailer in the sense that both are braking for themselves. Too little power to the trailer brakes, and the slowing or stopping the trailer falls to the tow vehicle brake system. Too much power to the trailer brakes, then the trailer brakes get the job of slowing or stopping the tow vehicle. Not set properly, then you’ll be needlessly wearing out the brake system of one or the other, and there’s a costly and unsafe proposition for sure.

Bottom line: It’s important to set the brake controller for the job at hand. For some, this will mean doing the initial setting, and tweaking the system to get everything honed to “towing perfection.” However, if you use your tow vehicle to tow different trailers – for example, using your pickup to haul your travel trailer, and then on other occasions using it to haul a utility trailer – the different trailer weights will require adjusting the controller more often. Horse trailer users find this a frequent issue – hauling maybe two horses today, one tomorrow, or “deadheading” with no load on at all.

Different brake controllers require different approaches to settings

That’s why it’s critical that you know what brake controller you have installed in your tow vehicle, and you have the manufacturer’s instructions on setup. Don’t have the instruction manual or quick setup guide? Get the manufacturer name and model number, hit the Internet, and look for it. If your controller is old enough not to have a presence on the Web, then it’s high time you got a new brake controller.

Brake control settings

However, some observations about brake control setting that apply across the board. Temperature makes a big difference. You’ll need to pre-warm your brakes prior to “dialing in” the right setting. Your manual will tell you how to do that. Then it gets dicey – you’re often told to engage the manual brake lever on the controller while cruising down the road, one suggests, “at 25 miles per hour or less.”

By the use of the manual engagement lever on the controller, you’ll be using the brakes on the trailer, not the tow vehicle. All very well and good, but if too much power is routed back to the trailer brakes and you’re cruising along at 25 miles per hour, you may have a BIG mess to clean up back in the trailer should the brakes lock up. At least one expert recommends checking your brakes in your driveway at, say, 5 miles per hour. The objective is to see to it that the power setting of the controller will slow the rig down – NOT lock the brakes.

We recommend finding an empty parking lot to do your adjustment. Doing so in a gravel lot gives us a lot more feedback than on pavement – you’ll hear that gravel if you lock up, and the skid marks are a clear indicator that you’ll need to back off the gain adjustment on the controller. Once we know where things sit on gravel, then fine-tuning on pavement ensures we have the controller set where it needs to be.



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1 year ago

Great question but nearly total failure to answer! The physics dont make sense either – the gravel test for lockup results in totally wrong setting on pavement. The gain control is NOT a limit against lockup but a ratio to truck braking. Etc. I keep meaning to write/film this question and can see it’s really needed. Another thing to note in any discussion of adjustment is that if the same rig needs incremental adjustment more than every 5000 miles, you should check your brakes aren’t wearing out/failing.

1 year ago

Thanks for this article, it is always helpful for those of us who are always looking to learn. From reading an article like this and adopting “testing” after every hook up we found out one day that our emergency brake cable switch went bad; it was part of our controller/brake testing for safety. In another case I had hit the adjustment knob, without knowing it, on the controller and by testing I recognized a problem and had to reach out to a forum to actually diagnose the issue.

Betty Danet
1 year ago

This is so important. We have a fifth wheel and we check the trailer brakes after every stop. Once when leaving a rest stop we had no brakes. The connections to the trailer plug had come loose due to a rough Interstate road. Another time we came to a downhill stop sign and heard a clunk from the hitch. It was a fuse this time. If the tow vehicle is doing all or most of the stopping, an emergency stop at high speed could be disastrous as the truck would stop but the trailer’s momentum would keep it moving forward. At the least, it would put serious stress on the hitch, might even break it. It is so crucial to have the gain set correctly and to check the brakes.

William McGullam Sr.
1 year ago

While I usually find these tips informative this one is a flop…. nothing telling me anything useful.

1 year ago

Well, the authors are writing for all readers of the newsletter. Happy that your knowledge is complete, but no need to make a comment as if this was intended just for you.

1 year ago

I agree with you. I was looking for an article on this subject to share with some potential RVers but decided this article’s content was so thin it would cause more confusion than clarity.

Betty Danet
1 year ago
Reply to  T G

If nothing else, the article makes people aware that trailer brakes are important and can be adjusted. Many people, especially newbies, do not know this. The article does say to check the manual or internet for your specific brand or model. It’s not like he just decided to write this, he was answering a reader’s question.

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