One brake over adjusted

[enahs]

On a new rig with less than 1500 miles, one self adjusting brake started to smoke. All others were fine. Factory says brakes were all adjusted during manufacture. Dexter says brakes can become under adjusted but not over adjusted on their own unless something is wrong with the brake. Had full, very competent service done. Concludes that brake and others are fine except the offending one was significantly over adjusted. OK, but why suddenly over adjusted. Can the self adjuster malfunction and do this? Not out since. We'll see!

[JBarca]

Fisherman wrote:
That is an interesting and very informative write up John, thanks.

Thanks, yes the learning is continuous. If one thinks they have it all figured out, then reality sets in and sets you straight, you don't know it "all". You do enough work on mechanical systems, stuff just happens!

When I had my drum run out issue on the self adjusting brakes, Dexter tech service tried to help, but back in 2009 they had not known (at at least that tech didn't) of what an excessive runout issue can cause. Here I was using that same camper on standard adjust since 2003 and the issue never reared it's head, that is until I installed the self adjusters.

I was not shocked that standard adjust brakes could have the same problem, but I at least had a heads up it might. Then we proved it when the drum gets bad enough, and the conditions are right, it can happen on standard adjust, but from a different source. While the standard adjust brake setup did not over adjust it self, gross run out of he drum can create a similar heat issue.

Thanks

John

[Fisherman]

That is an interesting and very informative write up John, thanks.

[JBarca]

enahs wrote:
I appreciate all of the potential scenarios. But none are consistent with the shop's alleged findings. All brakes are fine. No excessive wear. The offending brake was supposedly much over adjusted. But none of this showed up for 1500 miles. Now, just prior to the smoking event, there had been a lot of rain. And the trailer then sat for several days before heading home and encountering the smoking issue. I am wondering if this is a matter of a brake failing to release, a bit but not much over adjusted. In any case, in a few days we will give it a good test. If the problem reappears, all new components will be installed — brakes, bearings, drums. BTW, Dexter now does not plug the brake adjusting ports in the backing plates, There are two of them in each plate and they are left open. We've since properly plugged them.

Hi,

Just found your post. As a point of view from my background, I was one of the first here on RV net to report on installing self adjusting brakes upgrades from standard adjust. I had one wheel over adjust due to excessive drum runout. Dexter declares (or at least did then) 0.015" TIR is the spec for their drums max limit. My old Alko drum that worked on standard adjust was at 0.028" TIR and it allowed the brake to adjust into that excess clearance then then heat up badly. If you want to read more on this, see here I did a post on it in 2009 https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/23458294/srt/pa/pging/1/page/1

I also had a similar problem with my son's trailer that he bought used with standard adjust brakes. This would be like yours, just in his case it was on 5,200# axles so a 12 x 2" brake. Not sure what yours is, but the end result may not matter.

We did the brake adjustment ourselves on his camper after we inspected and greased the bearings. Jack up the camper, spin the wheel, tweak the adjuster to get the feel "you" want then make all 4 the same feel. We also do a drag test on gravel to make sure all 4 come close to lockup at the same time. This is about 6 months after he got it and maybe only ~ 500 - 1,000 miles on the camper after the adjust.

He went camping and started complaining he had a hot front left wheel. He could smell it. And the IR gun confirmed it, it's excessively hot. After the system cooled down, it was not as bad but the brake was grabby. We backed off 5 clicks and tried again. In a short while the same thing happened. A hot wheel, backed off another 5 clicks, same thing. And I know which way back off is.

After we backed off 20 plus clicks, OK something is messed up how this brake keeps getting so hot. Jack up the camper, with 20 plus clicks backed off, the wheel spins free as can be. This is a brake engagement issue.

Tried several checks and parts changes to back into what was the issue? Started with an amp check on the magnet coil in case it was pulling more power for some reason, nope. It was not the coil, we even changed the coil. No change, the wheel would still go into mega heat after only a few stops. And it needed stopping to get hot.

Changed the magnet arm with an older spare I had, thinking it would jam for some reason, nope no change.

Next we changed the entire brake plate, I had 4 Alko half used complete plates with shoes, magnets and adjusters left over from my self adjust upgrade. It changed nothing, the newly changed brake still would get hot. OK there is only one part left, the brake drum.

I have a 5,200# axle stub I can do a brake drum run out bench tests on. I first checked the diameter of the brake shoe surface, it measured 12.001" to 12.003"ID. OK, the shoe surface is round enough, but what about the run out to the bearings? Used the bearings from the camper in the drum and indicated it. The shoe surface is 0.025" TIR plus spinning out of round with the bearings.

I am from a machine shop background and have a pet peeve with the trailer industry on why they cannot machine a brake drum to spin at least within 0.005" TIR all day long. It's all in the setup of the machine.

Since my son was going to do a suspension bushing and shackle upgrade to bronze bushings and wet bolts, he bought all new brake drums and self adjusting brake plates. We indicated each new brake drum before putting them on. 2 of them were less then 0.005" TIR, the other 2 were less then 0.008" TIR so we put them on. The problem went away.

This is what I came to conclude from this standard adjust self brake up issue.

1. The brake drum was too far spinning out of round.
2. We manually adjusted the brakes to a slight drag feel with the wheel off the ground. It is common to have a drag spot and a skip no drag on trailer wheels as felt during this process. The drums runs out of round but you never know how much.
3. All 4 brakes where set to be the "most" efficient, not a lot of lost motion/play in the system.
4. When the problem brake engaged, the magnet arm moved the shoes into the gross run out area of the drum. As the wheel then turns to the tighter part of the drum, increased pressure is seen to create slip on the magnet. This magnet arm pressure creates more shoe pressure which creates more braking friction.
5.This wheel now starts getting hotter as it is doing more stopping then the other 3 brakes.
6. As the brake shoes start heating up, they can swell some, no idea how much but they can be closer to the drum with the heat expansion and the brake drum ID is getting smaller from the high heat expansion also. This make this issue even worse.
7. The heat keeps building and then the wheel can lock up partly when trying to stop. You can hear the tire skid.
8. As the system cools down and the brake disengages, the wheel spins free making this hard to figure out the issue.

Bottom line, an excessive run out on the brake drum shoe surface created this issue.

I suspect how the prior owner never found this, they never had the brakes adjusted very well or at all in it's prior life of 10 years. With the brakes very loose in adjustment, this issue may not have come to be found. It was only when we went in and adjusted them to where they were supposed to be did the issue flair up.

If you trust your shop did the right adjusting, I'm sure they may not have checked the run out of the brake drum. You have to have a bench setup with a spindle to do this off the camper, or take the entire brake plate off to get the indicator in to check the run out.

I'm not saying this is your issue, but it at least can explain how it can happen with what you told us.

Hope this helps.

John

[Matt_Colie]

Enahs,

It sounds like you have isolated the problem, now you need to fine the real cause. This can be an issue.

I used to work in quality for a Detroit first Tier. It became clear to me that unless quality programs are forced on most manufactures, they will not embrace them. The fact is, that there is very possibly a component of that brake that is the problem. It might not actually be out side of the manufacture's tolerances, but those tolerances may be quite worthless. Finding the problem part can also be a big problem. There is also no reason it has to be just one part.

Matt

[enahs]

Ran across something coincidentally. The arm that holds the magnet on manually adjusted brakes can, under certain circumstances, ride up on the back edge of the engaged brake shoe and then prevent the shoe from fully disengaging. One thing that can cause this is a worn or ill fitting bushing on that arm allowing excessive side play. I don't know that that is what happened here or why it should happen on new brakes. But it can be a cause of a hanging brake. And it is something to check for when doing a brake inspection.

[Gdetrailer]

Brake shoe could have gotten stuck and not releasing, possibility?

Sure, anything is possible.

With only 1500 miles on the rig it rules out brake parts being rusty, everything should still look like new.

Monitor things for now until you are satisfied everything is correct and good then move on if no issue is noticed after a another trip..

[enahs]

I appreciate all of the potential scenarios. But none are consistent with the shop's alleged findings. All brakes are fine. No excessive wear. The offending brake was supposedly much over adjusted. But none of this showed up for 1500 miles. Now, just prior to the smoking event, there had been a lot of rain. And the trailer then sat for several days before heading home and encountering the smoking issue. I am wondering if this is a matter of a brake failing to release, a bit but not much over adjusted. In any case, in a few days we will give it a good test. If the problem reappears, all new components will be installed — brakes, bearings, drums. BTW, Dexter now does not plug the brake adjusting ports in the backing plates, There are two of them in each plate and they are left open. We've since properly plugged them.

[Gdetrailer]

enahs wrote:
Not fretting but very curious. The shop is good. Does a lot of this work. I trust that brake was over adjusted. Question is how or why. It will be tested though.

How or why doesn't matter anymore if it was the problem in the first place. That brake nor any of the others can self tighten themselves unless it is equipped with the correct self adjusting parts (which yours is not supposed to have).

As to address the how and why, it comes down to these possible reasons..

#1 Dexter BOFFED the setting on one side of the axle setting it to tight on the assembly line.

#2 Dexter BOFFED the setting on one side of the axle setting it too loose, but that would require the next random axle that was added to the unit to have both brakes to be set too loose.

#3 Someone on the frame assembly line played mechanic and adjusted the brake adjustments with a screw driver setting one too tight.

#4 All brakes set correctly at Dexters assembly line, made it through the frame assembly line untouched and someone at dealer decided to mess around with the brakes.

#5 All brakes set correctly from Dexter, made it through frame assembly with no adjustments made and someone (your kid or Kids mechanic) adjusted them with a screw driver..

#6 Everything was setup correctly mechanically but you have an electrical problem (bad connections) with some or all brakes causing three of the brakes to wear down leaving only the one working and overloading it (smoking).

#7 The mechanic you took it to made up an excuse to charge you for labor to correct it.

#8 and so on..

Could go on all night with many, many scenarios on what may have happened but the scenario of one brake suddenly deciding to crank its adjustment up above 11 all by it's self is just not possible.

Those star wheels do not turn easily, I have to use a pair of Channel lock pliers to turn mine. Never been able to turn them by hand only, the spring that goes across the star wheel actually touches and holds the wheel from randomly turning. Makes a ping noise when I turn the star wheel at each notch.

It is possible that three of the brakes on the other wheels wore down a bit faster than the one that was smoking and those needed adjusted tighter and the one that was smoking was correctly adjusted..

The problem now is the proof is all gone and it is a guessing game as to what really happened.

What the mechanic says as to tight may have been in reality correctly set.. Only the mechanic knows for sure..

Did the mechanic struggle to get the drum off?

Or did it come off with some resistance?

Did the other three drums come off with zero resistance?

Some very slight resistance is normal and desired.. If any drums came off with zero resistance then issue was more likely those brakes were excessively worn down or needed to be adjusted tighter..

A lot of he said vs mechanic said, which is why I do all of my own brake maintenance..

In PA any trailer with brakes must have a annual safety inspection, I make sure that I am present and watching the mechanic at all times when they remove the drums for inspection..

It is for my own safety and sanity since now days many mechanics have zero clue about drum brakes..

And yes, I have had a few inspection mechanics that decided to check and "adjust" the brakes using the inspection hole.. And yes, I HAVE had to undo what they did through that hole when I got home by removing the drum and resetting the start wheel :E

[enahs]

Not fretting but very curious. The shop is good. Does a lot of this work. I trust that brake was over adjusted. Question is how or why. It will be tested though.

[Gdetrailer]

enahs wrote:
This RV belongs to my kids. An on the road check was sone to be sure it was not locked up, and the controller was backed way down. The shop repair and inspection were done only a couple miles from home. Just to be clear, I am more than familiar with electric brakes in all respects — repair, replace and adjust. The shop verdict is that the offending brake was seriously over adjusted. Yet, there had been no problem for 1500 miles, and the factory insists it was adjusted when new.. It appeared suddenly. Now everything is properly adjusted and it has been inspected. So the question is this: what would cause a non-self adjusting brake to suddenly become over adjusted? Dexter says it can't unless there is a brake "malfunction'". But they can't even suggest what that might be. Bad magnet? Intermittent short? These wheels and tires are on an in-cab monitor, so the temps will show if the problem returns. Its originally showed a slightly higher temp (5 or 6 degrees) but nothing dramatic. A passing motorist warned that the brake was smoking.

The answer is it CAN'T "overtighten", period.

There is absolutely nothing inside the brake drum that can turn the star wheel as long as it is not a "self adjusting" unit.

Self adjusting units have additional parts and one of those is a lever on a wire and has a spring to hold the wire to the star wheel. That lever is what makes the adjustment (IE turns the star wheel).

Without that lever, the star wheel is all by it's self and it is a screw and no, that screw cannot turn either way on its own as it is under heavy spring pressure from the brake shoes..

Here is a comparison pix..

Left is non self adjusting and right is self adjusting



I call BS on the shop you had it at and I suspect what really happened was the other three brakes were not adjusted correctly leading to that one brake doing the work of all four which will cause it to overheat and smoke.

The problem is, you obviously was not present when the shop pulled things apart and it is basically "hear say" as to what really happened.

You have it fixed, time to move on and not fret about this any longer.

[enahs]

This RV belongs to my kids. An on the road check was sone to be sure it was not locked up, and the controller was backed way down. The shop repair and inspection were done only a couple miles from home. Just to be clear, I am more than familiar with electric brakes in all respects — repair, replace and adjust. The shop verdict is that the offending brake was seriously over adjusted. Yet, there had been no problem for 1500 miles, and the factory insists it was adjusted when new.. It appeared suddenly. Now everything is properly adjusted and it has been inspected. So the question is this: what would cause a non-self adjusting brake to suddenly become over adjusted? Dexter says it can't unless there is a brake "malfunction'". But they can't even suggest what that might be. Bad magnet? Intermittent short? These wheels and tires are on an in-cab monitor, so the temps will show if the problem returns. Its originally showed a slightly higher temp (5 or 6 degrees) but nothing dramatic. A passing motorist warned that the brake was smoking.

[Grit_dog]

enahs wrote:
Dexter engineering says that since the brake can't over adjust itself, there must be a "malfunction" with the brake itself. But they are not suggesting what it might be and what we should look for!

So you had it “fixed” and presumably towed it home? Did you check the brake temps?
Or maybe I’m lost here….
FWIW, it is worth the cost of your “use” of the trailer to be able to do simple repairs, or in this case, adjustments, to keep you on the road doin your thing vs cutting a trip short or getting stranded or whatever.
I’m certain there is a YooToob tutorial on adjusting drum brakes. Requires only a screwdriver and a means to jack up a wheel. And a basic understanding of which way to adjust the star wheel manually.
Food for thought.

[Gdetrailer]

enahs wrote:

Roger10378 wrote:
Something is not right here. If the brakes were not adjusted right either at the factory are later they would not wait 1500 miles to overheat. Are you sure that you don't have a bearing problem?

I agree entirely. That's what bothers me. No sign of bearing failure. Bearings all checked and repacked. Brakes are apparently ok. Not clear why the problem occurred, which is bothersome. Dexter says once adjusted there is no way for the brake to become over adjusted on its own. We shall see.

Consider this, it is possible that the three OTHER brakes were UNDERADJUSTED from the factory, in other words the other three brakes were factory set too loose and were not providing much or no braking support leaving the only one set tighter to provide all of your braking.. That most certainly can cause the tighter brake to overheat and smoke..

Although in all of this, you should have noticed something wrong almost immediately.. I have had a wire break off at one of the backing plates several times over the yrs.. Each time I noticed the trailer giving a tug or pull in the opposite direction of the broken wire (IE wire broke on drivers side but pulled to the passenger side)..

Best to just make sure everything is adjusted correctly, wiring is good and move on.. Life is too short to fret about a few "what ifs"..

[enahs]

Dexter engineering says that since the brake can't over adjust itself, there must be a "malfunction" with the brake itself. But they are not suggesting what it might be and what we should look for!