Trailer brake help understanding.

[GN2018]

I use my truck like a car.  However, my daughter just bought a camper and I’ve told her she can use the truck anytime she wants.  So, we are learning and I have a question about the trailer break.  Basically, what is the procedure to set up the brakes when you connect the trailer.  The instructions say to go about 20 miles per hour and then press the slider switch.  Problem is, I don’t know how to tell if it’s set up correctly.  The owners manual seemed to indicate that you increase the brake gain until the wheels lock up.  Is there a good way to learn how to do this?  It just seems like something we better get right before we encounter an emergency stop and figure out we didn’t do it right.  Any help would be appreciated.

 

FWIW, I have a 2021 GMC Denali with the trailering package.  - Thanks.

[Carver60]

 

[Carver60]

 

[64BAwagon]

You can adjust brake gain at any time and many people will decrease the gain in wet or snow to prevent lockup. The amount of gain should be set to your preference. I run my 2024 3500HD at 6 while pulling our 13k fifth wheel. But that may not be enough for others. I prefer the trailer to do just a little less braking than the truck. In a panic stop they still grab plenty well. 

A good starting point is to find a road with no traffic. start with the gain set at 4 or 5. make a few slower speed stops and see if the trailer brakes more or less aggressive than  you want. Increase or decrease the gain to get the feel you want. I prefer this over the lockup method. After you get the feel right then try higher speed stops and adjust accordingly. It sounds way more complex than it really is. 

Also note that the gain setting needs will vary between trailers. Some trailers have well adjusted brakes with no contamination, others wont. My last 3 travel trailers had grease contamination due to blown seals from someone who had hands on it before me. They required a gain of 8 or 9 until I diagnosed and repaired them.  The size of the trailer will also dictate the gain needed. 

  Edit:  Keep in mind that trailer brakes require wheel rotation to apply the outward pressure of the shoes to the drum. The process of testing them from a stop is not going to yield an accurate result since the wheel must be turning in order for the magnet to exert force on the shoes to apply them. 

 

Edited April 14, 2025 by 64BAwagon

[64BAwagon]

Also note in the video that the lead axle was locking up and the rear wasnt. This is an indication of an unlevel trailer from a poorly adjusted hitch. The trailer needs to be level in order for both axles to do their fair share of work braking and carrying the load. I see nose high trailers on the road all the time, many from RV dealers. While a brand new, empty trailer might ride like this, once it is loaded and ready for use it may/should be checked for level and proper weight distribution. 

[asilverblazer]

Need to make the trailer brakes are adjusted as well - they almost never are. I adjust mine so that there is a noticeable drag when turning the wheel by hand.