Adjusting trailer brake controllers

Adjusting trailer brake controllers

By Russ and Tiña De Maris

brake-controller-2A 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

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6 thoughts on “Adjusting trailer brake controllers

  1. Ed Price

    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?

  2. Wolfe

    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.

  3. Wolfe

    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.

    NOTE THIS AS YOUR MAX SETTING. NEVER SET YOUR BRAKES HIGHER IN OPERATION. Locking brakes in motion is BAD news.

    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!

  4. Keira B

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

  5. peter

    Well that told me absolutely nothing.

  6. Joel Vinson

    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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