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I would suggest a trailer repair facility rather than “brake shop”. Someone who barely knows how to load an automotive drum on to their “automatic” drum machining fixture is going to give you the “deer in the headlights” look when you ask them to clean up the brake magnet surface.
TucsonJim
Just FYI, the four outer holes on your brake magnet are wear indicators. When they disappear it is time to replace the magnets. Can you tell how much depth they have left?
I know you said you are changing everything anyway, but curious how deep they are compared to the new ones you buy.
2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
Electricians were created because engineers need heroes too....
If you are not changing the magnets or sanding them, I might be inclined to forgo turning the inside of the drum as the magnet is already bedded to that profile.
I would agree with Jlawles2 Joseph on this . . . but, what has caused the grooves in the drum face and the magnet? Maybe the photo is making this look worse than it is? In my experience, those two surfaces wear smoothly. The magnetic field draws the two together, but brake apply force depends on friction between these two surfaces. There is some “float” to the magnet position. If the magnet shifted out of the “ridge and valley” alignment, brake apply would be significantly reduced. I would prefer to see these as two smooth surfaces.
Cate&Rob Your comment on grooving has me wondering. The magnet when activated clamps onto the drum and the rotation of the drum moves the brake magnet/lever and expands the shoes. All good. But the magnet must move in some form of arc not just one spot on the drum which usually results in a smooth brake and drum surface so grooves really shouldn't develop. Right?
Other than poor metallurgical properties of the drum, I think a weak magnet could be the cause. Unless it's all four...then, no.
I agree with Joseph and Rob, if they are grooved and you are surfacing the drums, replace the magnets, if you are not replacing the magnets, don't get the magnet's mating surface done.
On my previous 5'er, the magnets were still good after 15 years. No grooves.
Wow Jim! Pretty sure you were just looking for a yes or no answer eh? ..lol I'm still the outlier...still say no.
2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
Electricians were created because engineers need heroes too....
Of course . . . In line with the sub-purpose of this forum (spending other people’s money) . . . what you are contemplating spending is half way to the cost of EoH disc brakes which would bring you to a whole new world of performance and ease of maintenance.
The inexpensive fix to this is to just install new shoes and run the brakes until the magnets are due for replacement. Then replace it all unless a quality machine shop can be found and their fee is far less than a drum and bearing replacement. Most drums and rotors do not have the material to allow for reconditioning in our disposable world.
My opinion is that the parts look fine. The only concern would be the flatness of the magnet where it contacts the armature surface on the drum/hub. I believe there is a measurement threshold when a straight edge is held across the wear surface.
I dont know of any shop that will turn a trailer brake drum, cleaning up the armature surface is a whole different operation. Because of this my understanding was that no one will turn these type drums.
I also think the friction material on the shoes is more than adequate, youre not going to gain much by replacing them and this set is already mated together. As long as they were functioning well before the teardown I would clean them up and put it back together. https://www.dexteraxle.com/user_area...ice_manual.pdf
My opinion is that the parts look fine. The only concern would be the flatness of the magnet where it contacts the armature surface on the drum/hub. I believe there is a measurement threshold when a straight edge is held across the wear surface.
I dont know of any shop that will turn a trailer brake drum, cleaning up the armature surface is a whole different operation. Because of this my understanding was that no one will turn these type drums.
I also think the friction material on the shoes is more than adequate, youre not going to gain much by replacing them and this set is already mated together. As long as they were functioning well before the teardown I would clean them up and put it back together. https://www.dexteraxle.com/user_area...ice_manual.pdf
Pg 14,16 and 49 have the answers you seek.
While I believe if following the manual(s) I would have the shoes replaced before they reach 1/16 in thickness. When the friction material becomes this thin, heat rejection becomes and issue with bonded shoes.
I believe each person has their limits on what to spend and what to continue to use.
If a machine shop was found that could handle the drums, and there is enough material to recondition them, this would be an easy solution. The manual does imply that reconditioning is possible. Finding this shop would be a challenge these days.
My opinion is that the parts look fine. The only concern would be the flatness of the magnet where it contacts the armature surface on the drum/hub. I believe there is a measurement threshold when a straight edge is held across the wear surface.
TucsonJim , familytruckster4 's comments drove me to dig into my school documents again. The pic below is from a lecture. While not a "measurement", per se, but it does give a visual indication of normal vs abnormal magnet wear.
Oh--and I'm with Cate&Rob -- get disc brakes and don't look back.
Howard
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
Jim, I’ve gotten a lot stuff for my trailer at Wheel Equipment Inc on Randolph just off Ajo. Also if you want to compare the magnets to never been used ones, I have still in the box sets left over from when I switched to disc. Professional Trailer Repair is right behind Wheel Equipment, I would think one of them could turn the drums.
TucsonJim Jim - can you post a better picture of the ID of the drum, something more square on the surface? I'm in the camp of don't get them turned. Back in the automobile drum brake days, I almost never had good luck with turning, solving most problems with new drums. Almost everyone that does drum turning is not a machinist, and won't have the correct cutting tool setup, will hog off too much material, etc.
Ottertail, Minnesota
2022 Imagine 2500RL VIN 573TE3029N6637046
2022 Ford F-150 Lariat, SuperCrew, long box, max tow
First of off, thank each and every one of you for your input. This was an interesting discussion that went everywhere from don't do anything to replace with disc brakes! Hogdrv recommended a couple of places in Tucson to do some of the work. I made my first stop at Professional Trailer Repair. I didn't even know they existed. The shop is very busy, but the employees took a couple of minutes to discuss my brakes with me and I really felt like "these guys get it"! The shop was clean and organized, and you could tell they had their act together. Here's a synopsis of our conversation.
1. There is nothing wrong with my brakes. The magnets and drums are wearing normally on all four wheels. They estimate they're worn about 40-50% and still have a lot of life left. The ridges on the magnets and the armature surface on the drums are very typical of what they see. They said that if I replaced the magnets and drums, those marks would start appearing again after just a few thousand miles. As long as the wear holes on the magnets are still there, the coils aren't showing, and the magnets aren't wearing more on one edge than the other, they're fine. He recommended that I clean and lubricate the components where applicable and verify that the magnet arm is moving correctly and returning with the spring pressure. He did say to reinstall drums in the same position so the magnets and shoes match up with any wear that is already there. I marked the drums when I took them off to make sure they were in the same position when I put them back on.
2. They used to turn brake drums, but no longer do. The reasoning was that there is a lot of variability in the drums, and many of them don't have enough material left to make a clean path. Their rationale was that new drums are a cheap investment that isn't worth a shop maintaining a lathe and the labor that goes into the job.
3. The shop works on all kinds of trailers and there were a couple of Imagine trailers in there. They said that if I ever need any work done such as disc brakes in the future, I'm welcome to purchase the parts anywhere I want and they will just charge the labor. Current labor rates are $130 per hour.
So I'll pack the bearings and put it all back together.
Thanks again
Jim
Jim and Ginnie
2024 Solitude 310GK - 2020 F350 Dually
GDRV Technical Forum Moderator
GDRV Rally Support Coordinator
That is the right decision Jim, I think you will get a few more years out of those brakes. Maybe next year this time pull one to give it a check, all the miles you will put on this year it may be worth the effort.
Brian
Brian & Michelle
2018 Reflection 29RS
2022 Chevy 3500HD
When I was still working my guiding principal was always "if this was mine and I had to take the money out of my wallet for the repair, would I do it" Others would sometimes unload the parts cannon but I took a more balanced approach. Even then I got accused at times of being over cautious but I never compromised on brakes, tires or suspension pieces. Theres far too many ways that that could end badly, especially on emergency vehicles.
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