I need HELP!!!: One Brake Drum Very Hot

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One Brake Drum Very Hot

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Forum Name: I need HELP!!!
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URL: http://www.rpod-owners.com/forum_posts.asp?TID=15268
Printed Date: 08 Jun 2025 at 4:27am
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Topic: One Brake Drum Very Hot

Posted By: tmilliken
Subject: One Brake Drum Very Hot
Date Posted: 11 May 2022 at 6:53pm

Hello,

I recently purchased a 2017 RP178. I re-packed the bearings, replaced the seals and made sure the castle nut was adjusted correctly and took it out to test the brakes. After driving a couple miles, I checked the hubs and brake drums and noticed that one side was very hot and the other side was not at all. I jacked each wheel up and checked the brakes with the brake controller and both are working. When I spun the hot side, I could hear the brakes very slightly rubbing, but the wheel did spin freely. Should I not hear the brakes rubbing at all? Could that be why one side was very hot?

Cheers,

Tom

Replies:

Posted By: jeepers29
Date Posted: 12 May 2022 at 10:20am

It aounds like ypur brakes were sticking on the hot side or the cool side are not working at all.

Posted By: StephenH
Date Posted: 12 May 2022 at 1:03pm

You will hear a little dragging when spinning the wheel. The electromagnet contacts the drum lightly. When brakes are applied, the electromagnet increases contact and friction proportional to the current flow. This is what works to make the brake shoes tighten against the drum. When you release the brakes, the magnet stops being pulled into the drum, and the shoes retract by springs away from the drum.

How did you determine that both sides are working? Check the wiring to both sides.

-------------
StephenH
Happy is the man that findeth wisdom,...

http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods
Former RPod 179
Current Cherokee Grey Wolf 24 JS

Posted By: tmilliken
Date Posted: 12 May 2022 at 1:46pm

To test the brakes, I connected the trailer to the truck, jacked up each wheel and had someone apply the brake controller while the wheel was spinning. The brakes stopped the wheel and then was allowed to spin after releasing the controller. The brakes worked on both sides. I am thinking that the cool side may be adjusted looser than the right?

Posted By: StephenH
Date Posted: 12 May 2022 at 1:56pm

That is very possible. If so, the self-adjusting mechanism should adjust the loose one as you drive.

One other possibility is that the hot side is getting more current than the cold side. I'm not sure how you would check that, but a search (use advanced search to extend the date range) might list some possibilities.

-------------
StephenH
Happy is the man that findeth wisdom,...

http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods
Former RPod 179
Current Cherokee Grey Wolf 24 JS

Posted By: offgrid
Date Posted: 13 May 2022 at 6:40am

A slight dragging won't make the brakes that hot. It is much more likely that the cold drum is a indication that the brakes on that side are not working properly, even though the magnets appear to be activating both sides with the wheels off the pavement. Brakes are supposed to get hot when you use them, that's how they dissipate the energy from the moving vehicle to slow it down.

I had the cold drum problem and found it was caused by imbalanced magnets by measuring current to the individual magnets separately. They were quite different, even with new magnets.

You can make this measurements with a clamp on dc current meter but you have to keep the the clamp far from the magnets or the magnetic fields will cause the clamp on Hall effect meter to be inaccurate. Best to put the clamp on up near the 7 way connector and then connect one magnet at a time.

That also gives you the chance to get rid of the crummy insulation displacement connectors foods have. Replace those either with good self sealing heat shrink butt splices or with soldered connections.

Once I determined that imbalanced magnets were the problem I disconnected the good brake and made several stops with the weak brake only, following Lipperts brake burnishing procedure, because the weak brake never got a chance to get burnished in properly while both were operating.

Then, to force the magnets to have the same current I rewired them in series rather than parallel as they are normally and turned the gain all the way up on my brake controller to compensate as much as possible for the lower voltage at each magnet from the series connection.

Even then my brakes were not fully balanced (as measured using an IR thermometer after a couple hard stops), but they were at much better.

Bottom line is that electromagnetic trailer brakes are crude, antiquated junk by today's standards and there is only so much you can do to get them to be balanced and work as they should. That's not to say you aren't right to try, I found that brakes that grabbed on one side more than the other were much worse especially on wet pavement, than ones that were balance but a bit weak.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: tmilliken
Date Posted: 14 May 2022 at 8:41am

That makes sense that the cold side maybe isn’t getting enough current. I will try that test.

Thanks for all the replies.