Sunday, September 19, 2021
Sunday, September 19, 2021

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.

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.

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.

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.

##RVT772 ##RVDT1261


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Philip The Commercial Driver Examiner
10 months ago

Tried and true method taken from a trailer brake control manual years ago.

“On the type of surface you expect to be driving on and at a low speed fully activate the trailer brake hand lever, now increase the controller input setting until the trailer tires just begin to lock up with the hand control lever fully activated. Decrease the controller setting by one full number and your brakes are now properly adjusted. Repeat this procedure when your trailer weight or road conditions change.”

I’ve used this method for years and it’s perfect. What it does is make the trailer brakes activate to the point where if you make a full brake application with the tow vehicle the trailer will brake to its maximum possible without locking up. If you are on a wet or slippery road and you adjust with this technique it matches the available traction perfectly, also if you are hauling a cargo trailer loaded or empty and you use this technique it compensates perfectly for specific trailer weight.

Emma H
1 year ago

Thank for your information you provide. But I have a advice: You need to take the temperature of the brakes into consideration before making adjustments to the brake controller settings. You will need to heat your brakes a bit before you make any settings to the brake controller.

To do this, pull up the manual brake lever on the brake controller while you are driving down the road at around 25mph. Since you will need to engage the brakes at the trailer side, bring along a companion to pull on the brakes for you.

Emma H
1 year ago
Reply to  Emma H

More information in here. I think someone will need. Thanks!

1 year ago

Not sure I like the gravel method unless if you set the trailer so that it just skids on the gravel then it should be about right for pavement where the tires will have more traction and shouldn’t skid. Of course this goes out the window if pavement is wet where you may need to back it off even from the gravel skid point.
I like my method the best. Just go slow at first, 5mph, apply vehicle brakes to see if trailer is braking at all, adjust until you feel the trailer braking some but not skidding. Go a little faster, 20mph, apply brakes to see if you feel trailer braking, adjust just a little more if necessary. By this time I am at the stop sign before pulling out on the hiway. If trailer and vehicle seem balanced when pulling up to the stop sign, I go with it, if not pull on across hiway, onto side road and continue playing with it until it feels right. A little experience with this and you will just know when it’s set right and when it’s not. There is no magic formula that anybody can give you that’s better than the”seat of your pants”

1 year ago

Just a minor note … most trailers still use brake SHOES to press against the drum from an electric actuator. If they have pads they are disc brakes and swueeze a rotor between the pads … probably not electric though.

1 year ago

That made absolutely no sense what so ever. I see these numbers and I am still confused if not more so then ever. Think I will take mine in to do this. Otherwise this really was no help. Thanks for the reading. Rocket scientist I am not.

1 year ago
Reply to  jillie

Think of the number as a percentage of total braking force. Some will read 10, have seen a few that read 100 as the top. That is 100% of total braking force, which just like in your vehicle if you use that much force you will lock up and skid. What you are looking for is the percentage of braking force necessary to help slow the vehicle. There is no right answer unfortunately, even with all other things being equal brake controllers will all respond a little different. You will also have to make changes as you go to battle things like brake fade after a hard braking situation. I like to start at 50% power and go from there.

Donald N Wright
1 year ago

Photographs of the brake controller would be helpful.

Ralph Pinney
1 year ago

The brakes on the trailer should be adjusted properly before starting the process of setting to set the trailer brake controller.

Ed Price
4 years ago

The trailer brakes should apply the proper amount of braking force (for any load or speed). The “proper amount” of braking is just what is necessary for the trailer brakes to slow the trailer at the same rate as the tow vehicle brakes slow the tow vehicle. That’s a complicated way of saying that the trailer brakes should do their share of the braking, but no more and no less. So how do you know when the trailer brakes are doing “their share?” I think it’s pretty simple; it’s when the trailer neither pushes on the hitch coupling (too little braking) or pulls on the hitch (too much braking). Sensing force at the hitch coupling and using that to control the trailer brakes is what the old hydraulic piston brake system used to do, and I don’t know why modern electronic systems can’t use an electronic force sensor at the hitch to control the electric trailer brakes the same way. With an electronic system, you could still provide for manual braking if desired, and also provide for manual off for special maneuvering (like backing up a driveway) when needed. Why do we still have stupid electronic systems with a sensor based on inertia inside the towing vehicle when we could do it the right way from hitch force feedback?

1 year ago
Reply to  Ed Price

Ed, you make very good points and although I do think someone somewhere may have solved the issue you raise, there’s a little more to this.

There is no ideal setting, because weather, (ice rain snow etc) road conditions and terrain play very big roles.

Imagine the ideal setting to get you stopped fair and even on flat level ground, with no wind at your back or facing you, then compare on a long mountainous down grade on the Rogers Pass in the Canadian Rockies. Not the same.

My advice to folks for a long long time is to get setup like the advice given here and in almost every company doing these installs, then SLOW DOWN.

The largest contributor to RV disasters on our roads is failing to control the rig in an emergency, most often related to speed travelled.

Very few people who set out with an RV of any size have the training, experience or are naturally hard wired to deal with what happens to the mass of their rig when it goes haywire in a narrow environment.

Its a tough apprenticeship when it does – the results often not very pretty.

4 years ago

BTW: issues of brake/hitch wear, passenger comfort, and “trailer mess” are really secondary. Death is primary.

The DEADLY issue with badly misadjusted brakes is that all(?) tow vehicles now have antilock brakes and trailers never(?) do… As a result, in a panic stop, less experienced or scared drivers jam on their brakes, the tow begins to stop well, the over aggressive trailer breaks traction and acts like its on ball bearings, whipping around jackknife fashion until it regains traction, snags, rolls, and takes the innocent tow along for the ride.

If the brakes are set too light, you’ll overload the tow vehicle brakes, taking either insanely forever to come to a stop in a straight line, or fishtailing when you brake in a turn and the trailer doesn’t. Either has the same nasty end result.

…just so people understand the importance.

4 years ago

Since this gave no helpful tips for adjustment, here’s my max and gain methods that I read nowhere else:
1) Turn your gain higher than you expect neccessary, as a starting place.
2) From a dead stop, use the manual lever to apply that set-maximum to your trailer brakes. Caution: work fast, because you don’t want to overheat your brakes holding it maxed for long.
3) Using a low gear and preferrably on gravel, drag your rig a LITTLE, confirming the brakes are indeed locking.
4) Quickly dial the gain downward until the brakes unlock and wheels turn again.


5) Accelerate to 10-20mph, and come to a “typical urgency” stop again.
6A) If the trailer drags the tow (likely if still set near max allowed), turn down the gain until you can’t feel the trailer during stopping.
6B) If the trailer kicks/shoves the trailer, turn up the gain until you can’t feel the trailer during stopping. If you don’t have separate gain and max controls, again, do NOT exceed the max setting, ever.

You should now be set for best brake performance. That said, changing trailer weight (water tanks full?) or brake wear may require tweaking if drag/shove recur.

7) If you have a controller with advanced profiles (eg. Tekonsha P3) try the different boost profiles and/or speed compensated braking until you brake smoothly from any speed. That said, the LOW speed brake force setting is the most important once you prevent locking.

Hope this is helpful!

1 year ago
Reply to  Wolfe

Either use the manufacturer’s manual or don’t tow ANYTHING!

Keira B
4 years ago

Wow, the author of this article obviously is no expert on trailer brakes.

4 years ago

Well that told me absolutely nothing.

Joel Vinson
4 years ago

We pull a TT weighing around 7,100# with a ’15 F250. I do a manual brake check rolling down the driveway, when we leave. I have my gain at 7.5% and that seems like a good balance. I also use my exhaust brake when towing. That alone is an awesome addition over our last truck.

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