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E_J_push_n_wind's avatar
May 18, 2014

Are all of your trailer brakes working and how do you know?

I posted this question in General RVing because I wanted this question to get as much exposure as possible, I think this forum gives it more exposure than it would get in towing or on the technical forum.

Anyhow,we all assume that all is well with our trailer brakes when we head out if we give the manual actuator a "throw" and we feel the trailer respond. After all, why would you think anything else?

Well, I just got back from a 3300 mile trip to WA state and back and if I wouldn't have had a Fluke Ti100 thermal imager with me. I would have been in the dark.

As it turns out, I borrowed one from work (wonderful they let us do that) to take with me on the trip for the purpose of "scanning" the wheels and what not just to keep everything in check. I found out two things on the trip amongst other things. 1) I had one brake dragging and eventually one brake failed, both on the same side. Now, the brake that was dragging I know was dragging because it was running hotter that the rest when I stopped for gas and got a temp reading on the wheel assembly. It was reading upwards of 196 degrees and the other three were reading at about 160 degrees. I crawled under the TT and backed off on the adjuster a few clicks. It got me to thinking, this is the same wheel I had a blowout on back in June. Could have been the wheel just got to hot and caused the tire to fail. The Jury is still out on that one because I have no way to confirm that but it stands to reason that it could have been the reason for the tire failure. Especially since I had two failures on the same wheel inside of 6 months.

Secondly, the brake on the same side on the front axle failed. Again I know this because after reading at each stop for gas and all of the brakes running about the same temp of about 160 + or - a few degrees, that one in particualr read 86 degrees upon stopping and reading it. With a thermal immager you can see what is going on. The perimeter of the drum would of course show the hotest (bright red) and you could see the rest of the of the wheel assembly and their various temperatures as well. The imager discriminates very well as well so there is no confusing what is going on.

As it turns out, after getting the TT out of the shop and talking with the service manager, I had a magnet failure. The wire came loose internally. I asked him if it looked like the magnet had failed from day one and there was no ware on the brakes or if it looked like they were working and at some point it failed. He said it looked like it was working and at some point failed.

So, I pose the question. How would you know if you had a magnet failure or some other brake failure (electric brakes) short of all four not engaging? When I would brake, everything felt normal. No pull to one side or the other. I had effectively 75% braking which aint bad, but it ain't great either!
  • Not likely your wire broke inside of the magnet after a while. More likely the wire within the drum rubbed through on the linkage somewhere. Then it shorted or broke. That is what can happen over time.

    If your drum temps are running about 86 degrees with no brakes operational and are running at 160 degrees with brakes operational, then your brakes are not adjusted properly. But then again, you should not be checking your drum temps right after you use our brakes when pulling into a rest area. let them cool for a few minutes. Same reason you don't check tire temps after running. Of course they're going to be higher.
  • Just going by what he said, I didn't actually see it afterward. As far as the brakes, I only began to read them because of the 196 degree brake I saw through the wheel when scanning. It was "redder" on the imager than the rest and that is what got my attention. Again, my initial reading was looking at the hubs only but I could not ignore what I saw through the imager considering right after braking one brake only was 40 degrees hotter than the other three. Only after that did I begin to look at the brakes to makes sure my loosening the adjuster made a difference. Eventually it did after several small adjustments. It was the same noticing the brake that failed. I should have seen "red" using the imager on the perimeter of the drum after coming to a stop. It looked as cool as a pop cicle so that too got my attention.

    After this experience, I'm gunshy or even paranoid now. Not that it was a life threatening experience or that the trailer exploded or anything like that but now I feel like I have to have something that will give me an idea of what is going on with the wheel hubs/brakes. I even shot the temp of the differential just to get an idea of what was going on with it. I shot everything that generated heat including the radiator, condensor actually as that is what is up front.

    It's really a fun/neat tool to have along but as jmtandem stated it is more than one practically needs. It is really pricy and if I would have had to buy it, it wouldn’t have come along. I’m glad it was available. If ever I had to buy one, it would probably be one of those Harbor Freight ones that was mentioned.
  • It's really a fun/neat tool to have along but as jmtandem stated it is more than one practically needs. It is really pricy and if I would have had to buy it, it wouldn’t have come along. I’m glad it was available. If ever I had to buy one, it would probably be one of those Harbor Freight ones that was mentioned.


    I found the inexpensive Harbor Freight infrared temp probe to be within two degrees accuracy or so. I think for $39 they are all that is really needed to determine if you are going to have a brake or hub problem. I have even tested it against my body temp and it was right on. For trailering they are all that is really needed. Not saying that fancy high tech stuff is not fun to play with as it certainly can be.

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