Troubleshooting Brake Actuating Arm Breaking on a Trailer Brake Assembly

Updated 11/03/2025 | Published 09/30/2014

Question:

I have electric brakes on a triple axle trailer I dont have any problems to speak of with the brakes on the left side of the axles, but the right side brakes keep snapping the magnet off of the brake activator arm. We are on a trip and in two days have broken three magnets from the brake activator arm on the right side. One was on for a year, one for six months and one was put on just before we left on this trip. The power goes down one side of the trailer and feeds both sides of each axle and the ground is on the same side of the axle where the power is. Any ideas???

asked by: Dennis N

Expert Reply:

First thing I would do is pull off the hub and inspect the inside surface where the brake magnet rides. If it isn't completely smooth it could be grabbing the magnet and breaking it. Most likely you would have needed to replace the hub after the first time the magnet broke.

Are you sure you are using the correct orientated assembly? Brake assemblies are sold in right hand and left hand versions. The actuating arm of the assembly should be pointing towards the front of the trailer.

In order to pick out the correct hub assembly for a trailer you are going to need know a few key pieces of information. The first thing you will need to know is the bolt pattern of your hubs. This is so you get a hub that is compatible with your wheels. I attached an FAQ article on determining bolt pattern for you to check out.

Next thing you will need to know is what spindle you have on your trailer. In order to do that you can either get the inner and outer bearing numbers from a hub or use a dial caliper to get exact measurements of the spindle. The measurements needed are the parts of the spindle where the bearings ride.

If you get back to me with that information I will help you pick out the right hub assemblies. Or, you can follow the link I attached that will take you to the page that has all of our replacement hubs.

You would want to first select the bolt pattern that you have, next select the inner bearing you have, followed by selecting your outer bearing, and then all the correct hubs will be listed.

expert reply by: Jameson C

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Mike H.

11/1/2025

I am having the same issue as Dennis. Jameson, your reply did not help at all. We want to determine the cause of the magnet mount failure. My hub is perfectly smooth where it comes into contact with the magnet. Yes, I have the correct brake assembly for the proper side. What would cause the actuator arm to break off?

Jameson C.

11/3/2025

@MikeH Has more than one broken off? If it's just the one I'd assume a manufacturing error.

Mike H.

11/3/2025

@JamesonC Thank you for replying. Yes, both magnets on the passengers side (right side) have broke off. They are 7k Lippert torsion axels, one year old with an estimated 1500 miles on them. I talked with the dealer I purchased the trailer from and they said they have never seen this happen before. Again the surface on the hub where the magnet rides is smooth with zero imperfections.