Question about trailer brakes

[CampCritter]

My brake coils on a Dexter 3500 pound axle are not wearing flat. There is a ridge at the bottom of the coil as if that portion of the coil is beyond the armature on the hub and isn't seeing the wear that the rest of the coil gets.

The ridge is quite noticeable and I'd estimate it at about 1/16" high.

The Dexter manual states that the magnets should be replaced if worn unevenly or abnormally.

Manuals are not always correct though. Has anyone seen this type of wear? Is it normal? If not, what can I do to prevent it? Should I replace the coils?

[CampCritter]

ScottG wrote:
That's just the area that runs against the drum. Your magnets wear dots are gone so it's time to replace them.

Thank you! I was wondering about those holes. The Dexter manual says that, "the magnets should by replaced if any part of the magnet coil has become visible through the friction material facing of the magnet." It doesn't mention the dots at all.

[CampCritter]

Lynnmor wrote:
That is the way the junk wears. You can resurface the magnet to get it flat again, and also resurface the brake drum armature. Few shops are equipped with the equipment to do the drums and few can get the high finish required. Usually the armature has a limit of .030" stock removal. I have the equipment to do my own.

Brake manufactures install linings that work very poorly till they are burnished and they recommend doing a process to work the he!! out of them in their "burnishing" process. Well guess what, the magnets aren't seated yet and they are worked too hard with the hard use and high settings. So you either break in the new brakes with them operating poorly or you start the process you have just seen. Of course the delivery guy already abused the brakes before the trailer was ever sold.

I suspect that what is going on is that brake coil in it's unenergized position has its outer edge hanging off the edge of the armature. If Dexter added an 1/8" or maybe even 3/16" to the outer circumference of the armature, then I wouldn't be having this problem. I've wondered if I have drums that were manufactured wrong or perhaps I've got the wrong hubs. That's why I was curious if other people have seen this problem.

[CampCritter]

Boomerweps wrote:
Ballpark mileage on those brakes?
For that wear on the magnets, the drum must have a groove in it. If everything works and the drum groove isn't too deep, I'd just use it as is. Other wise, if you replace the magnet, you need to replace the drum or the new magnet will wear the same as the old one.

Those brakes have got close to 24,000 miles on them. This will be the third time that I've cleaned and repacked the wheel bearings and also cleaned, lubed, and adjusted the brakes.

I bought the trailer new and each time I've worked on the brakes, I've seen that ridge. Last year I got a little ambitious and filed the ridge off. The brakes for the most part work fine. If I have the amperage turned up too much, I do get some surging.

Your comment about a groove on the hub (actually the armature) is interesting. I was in a hurry today to take things apart, take pictures, and then put it all back together. I didn't spend as much time as I should have inspecting the parts. I do think I see in the picture a groove near the outer circumference of the armature. That groove is much wider than the ridge on the magnet though. I don't know how deep it is.

[CampCritter]

Cummins12V98 wrote:
You are part way there. Rip that junk off and replace with disk brakes.

I like the simplicity of disk brakes too, but I looked at the Dexter website and found the price for the disk brake retrofit kit. It's about $800 per side. Even if I shopped around and found the kits at half price, that's still more money than I want to spend.

Dexter Disc Brakes

[ScottG]

That's just the area that runs against the drum. Your magnets wear dots are gone so it's time to replace them.

[Lynnmor]

That is the way the junk wears. You can resurface the magnet to get it flat again, and also resurface the brake drum armature. Few shops are equipped with the equipment to do the drums and few can get the high finish required. Usually the armature has a limit of .030" stock removal. I have the equipment to do my own.

Brake manufactures install linings that work very poorly till they are burnished and they recommend doing a process to work the he!! out of them in their "burnishing" process. Well guess what, the magnets aren't seated yet and they are worked too hard with the hard use and high settings. So you either break in the new brakes with them operating poorly or you start the process you have just seen. Of course the delivery guy already abused the brakes before the trailer was ever sold.

[Boomerweps]

Ballpark mileage on those brakes?
For that wear on the magnets, the drum must have a groove in it. If everything works and the drum groove isn't too deep, I'd just use it as is. Other wise, if you replace the magnet, you need to replace the drum or the new magnet will wear the same as the old one.

[Cummins12V98]

You are part way there. Rip that junk off and replace with disk brakes.