There are a variety of reasons that cause semi-trailer brakes to lock up. If you’re having trouble with the brakes on your trailer, consider the reasons below. Inspect each one of the brakes on your trailer to determine the source of the issue.
In general, semi-trailer brakes lock up for one of the following reasons:
- Broken or worn brake shoes
- Failure of the brake controller
- Grease or other residues on the brake shoes
- Poor adjustment of the brake controller
- Poorly installed brake shoes
Keep reading to learn more about each of these issues. We will also provide some tips on how to remedy the problem.
Reasons Why Semi-Trailer Brakes Lock Up
Semi-trailer brakes operate on electromagnetic current.
The electromagnet is attached to an arm inside the brake drum and is linked to the brake shoes. When force or current is applied to the brakes, the magnet is attracted to the drum, which causes the arm to extend the shoes towards the drum. When the two touch, it causes friction and slows the vehicle down.
Failure of the Brake Controller
When the brake controller fails, the entire brake configuration will stop working.
You can test for controller failure by attaching the trailer to another tow vehicle. If it works on that vehicle and not on the other, it is likely that you have a failed controller. In most cases, the only way to fix a failed controller is to replace it.
Poor Adjustment of the Brake Controller
If both wheels are locking up, it’s highly likely that the situation is being caused by poor adjustment in your controller. Use the adjustment knobs to make the necessary corrections to the controller.
Every controller is different, so look at the manufacturer’s specifications to learn how yours should be set up.
Grease or Other Residues on the Brake Shoes
The tell-tale sign of grease or residue is if only one wheel is locking up instead of two. If this is the case for you:
- Jack up the vehicle and remove the wheel and brake drum.
- Inspect the brake shoes and brake drum for grease, dust, or other residues.
- If you find foreign material, be sure to clean it off with rubbing alcohol or another product that can cut through the grease.
Broken or Worn Brake Shoes
When you jack up the vehicle to look for grease or residue, you should also look for broken or heavily worn brake shoes and springs. If you find that they are broken or worn, they need to be replaced on both sides.
This is a huge safety concern for you and the other drivers on the road, so the worn brake shoes should be replaced immediately.
Poorly Installed Brake Shoes
Last, but not least, you may find that your brake shoes are just not installed properly or are poorly adjusted. If you’ve checked for the other four items listed above and haven’t found any issues, this is the likely cause of your brake problems.
Pull the drums and shoes off, readjust them, and put them back on. This will likely solve the issue.
Electric Brake Failure Due to Bad Wiring
With electric brake systems, there could be a wiring problem if the brakes keep locking up. If the wires are installed incorrectly or have become loose, the brakes could fail.
Here are a few things to check for:
Bad Electrical Ground
The main ground wire on the vehicle should be attached to a clean metal surface. It should be free of corrosion or damage, as well. The trailer ground wires should be in great condition and also attached to a bare metal surface.
Inspecting for poor ground connections should be a regular part of routine maintenance. If you discover any damage, repair or replace the wires immediately.
Bad Wiring or Shorted Wires
Inspect the power wires for:
- Damage
- Corrosion
- Loose connections that could cause brake failure
Much like the ground wires, the power wires should be in good condition and securely fastened. You can also use a circuit testing tool by connecting it to your main power wires and applying the brakes. It will tell you whether or not you have a good connection.
Final Thoughts
Towing a vehicle on the road comes with a variety of responsibilities and risks. Ultimately, it’s up to you to make sure that your semi-trailer brakes are functioning properly to protect yourself and others from injury. If you’re not sure how to do some of the items on this list, have the trailer inspected by a professional, but get the problems resolved immediately.
