Dexter Nev-R-Adjust hub out-of-round

Thanks for reporting back.

All 4 were over 0.015" TIR, yeh, the good ole trailer industry strikes again. Why they cannot machine the drums from new well under 0.005" TIR is just plain poor. The Auto industry can do 0.0005" TIR on disk brake rotors, they just have a different standard and spec.

Your shop who did the work, for $12.50 each, that is a deal for good work. Glad you found them.

In the end, all 4 drums were taken to an honest machine shop I trust, and all 4 out of round, all more than 0.15. I no longer feel the shuddering when I hit the brakes, just a smooth stop.

If you do this, ask them to wash the drums out in their parts washer. Otherwise you have to clean the bits of metal out.

They charged me a whopping $12.50 per drum.

Timeking wrote:
This trailer is a 2018 Rockwood. I took 2 drums to a shop, and they were both out-of-round by 0.020-0.030. Dexter spec is 0.015 or less.

I am concerned about "chamfer" centering reply above. What does chamfer mean? I can't find anything regarding chamfer and brakes other than slotted pads or rotors. confused.


Qhote: (I had him shut the machine off. What we found was his machine used the the hubs chamfer to center the hub. The chamfer was turned off center at the factory. The chamfer did not locate anything but was for clearance only.
I took the hubs and found a shop that use the hubs centers for machining.)

Hi Timeking,

I am the original poster from 2010 on this post who talked about the drums running out of tolerance. This post.
Dexter Self Adjusting Brakes (long W/pics and details)

Sorry I did not see this earlier to try and help. Reading the responses, there may be some confusion on what the real problem is.

First off. Someone mentioned the drum issue can be found with a micrometer. Well, it depends what you are looking for. It will not very accurately explain how much the drum brake shoe surface spins in relation to the axle bearings. But, a micrometer could tell you if the physical brake shoe surface is out of round standing still. Out of round meaning the ID of the drum shoe surface is elliptical. The 2 checks are very different and tell different things. Both, can be a problem and both can cause the brakes to overadjust. However, I would say that the drum brake shoe surface being out of round/elliptical is less likely.

And then there is talk of setting up a lathe to run true to a chamfer to use in turning the brake shoe surface. That shop did not do the procedure right. The lathe operator was inexperienced in trailer wheels or even auto wheels. The "chamfer" is a lead in angle to help the bearing race or the grease seal to get started into the hole. It really means nothing in relation to the brake shoe surface spinning true or the wheel bearings. Just forget about trying to use the chamfer.

You stated,

I took 2 drums to a shop, and they were both out-of-round by 0.020-0.030.

Thats a boat load. The generic shop talk of "out of round" on a brake drums many times means, the brake shoe surface is not spinning true to the bearing surface. BUT, from the words posted you cannot tell if that meant, an elliptical ID of the brake shoe surface OR that the brake shoe surface did not spin true to the bearing mounting surface? Or a combo of both?

Part of the problem is how a mechanic can easily check with an indicator on the trailer how much the brake shoe surface spins out of round with the bearings mounting surface. It is not quick to do this on the trailer itself with the actual brake plates still mounted.

I happen to have a old axle spindle I kept just to do this check. You yourself can do this, if you have a dial indicator and remove the brake plate off the axle and then mount the brake drum with bearings in it on the spindle. Then set up the indicator mounted rigid to the axle or a leaf spring rigid to the axle with the feeling plunger on the brake shoe surface diameter. Zero out the dial on the indicator, sharpie mark the starting spot on the drum and slowly spin the drum 360 deg. Make sure you come back 0.000" on the indicator when reach the starting position. If the 0 marks moved, the setup of the indicator is bad or the bearings are bad/loose. Fix the issue of not come back to 0 and try again. Yes, that is a lot of work, it means taking the whole brake apart or at least unbolting the brake plate and leave all the parts on it. BUT, that test either on the axle or on your own test axle is the correct way to do this test.

My drums, new and old that had a lot of runout (runout means a measure of distance 2 surfaces that are off center. A runout of 0.0000" means it is dead center within 4 decimal places) my drums where machined wrong from day one.

If you are concerned if you shop turned the drums correctly, doing the indicator test I mentioned above would confirm they did it correctly. Even a harbor freight 3 decimal place indicator setup correctly will work. Or find a buddy who knows how to use one and he brings his and check them. But he will have to do it on the trailer.


Curious, by chance do you know if your shop used a brake lathe or a conventional engine lathe? Both can be used, the setup is different but both when setup correctly can work well.

I asked my local NAPA shop what tolerance they could hold on turning my brake drums? They said they would turn it within tolerance. I again asked, what is the tolerance? He did not know or could tell me and I thanked him for his time and left. Shops that know what they are doing, can do this right easily. Shops who don't know, are clueless. But I come from a machine shop background so I'm more picky and know how good they can be.

Hope this helps

John

I still don't understand how you 'center' on a 'chamfer'. From what little I understood from the guy in the shop I took my drums to, he put some thing into where the races are, but said it was designed so the races don't get damaged. I'm out of my depth, and googling for hours leaves me more confused.

What is a "mounting surface"?

A chamfer is simply an angle on a corner for clearance, a brake drum needs to be located by the mounting surface. My opinion is that the .015” tolerance is still way too much and should be less than .005”. I turn my own in my shop.

This trailer is a 2018 Rockwood. I took 2 drums to a shop, and they were both out-of-round by 0.020-0.030. Dexter spec is 0.015 or less.

I am concerned about "chamfer" centering reply above. What does chamfer mean? I can't find anything regarding chamfer and brakes other than slotted pads or rotors. confused.


Qhote: (I had him shut the machine off. What we found was his machine used the the hubs chamfer to center the hub. The chamfer was turned off center at the factory. The chamfer did not locate anything but was for clearance only.
I took the hubs and found a shop that use the hubs centers for machining.)

Thanks ScottG.

I check suspected out of round drums with a dial indicator with a mag base. I've had pulsating brakes that checked round. The problem was brake material displacement on the drums surface wasn't the same ....which caused the brake pedal to pulsate. Same with brake rotors.

I've also had a new guy with his new brake shop set up on my trucks brake drums.
I had checked these drums with my dial indicator and all were perfectly round When he started the machine on the first one the cutter only contacted half the drums brake surface . I had him shut the machine off. What we found was his machine used the the hubs chamfer to center the hub. The chamfer was turned off center at the factory. The chamfer did not locate anything but was for clearance only.
I took the hubs and found =a shop that use the hubs centers for machining.

Timeking wrote:
OK so what should I do?

I would have them turned. Shop should also have a micrometer to tell you in advance if they are out of round. Will still have to charge some just to set it up and measure.

Best to have the magnet surface turned also but not critical. And a good general inspection of the mechanical situation and movement of the shoes and hardware.

The ultimate fix would be to go disk. Ugg or back to manual adjusted drums.

If just the drums are out of round, get them turned. No need to replace everything unless the brakes shoes and magnets are worn.
Turned drums will probably be better than new ones.

My last TT had Alko axles and the drums were out of round from the factory. I lived with it and the poor braking that came with it. New TT has same size brakes (self adj) but drums are fine. Although the new TT weighs a ton more, it stops better.