Shinkers

Hopefully someone here will have some ideas...

I have a couple of Paul Components track and freewheel hubs laced to some mountain rims. One hub has track threads and the other has normal freewheel threads. The drive side bearing sits within these threads and the freewheel threads over and bottoms on a shoulder at the base of them.

I've had a lot of bearing problems with these hubs. The drive side bearing seems to get tight and crunchy after only a couple of rides. I was experimenting with bearing preload when I realized that as soon as I back the freewheel off, the bearing feels fine. And then when I tighten it against the shoulder of the hub again, the bearing feels tight (tight enough that the axle spins inside of the bearing rather than the bearing itself turning).

What I'm thinking is that the freewheel is compressing the threads around the bearing and that's why it gets tight. But I don't know why that only happens when the freewheel tightens up against the shoulder of the hub. If it's just loosely threaded on the bearing feels fine. I've tried adding a spacer under the freewheel and that didn't help. I also threaded the freewheel on backwards to ensure that the threads don't capture the end of the threads on the hub. I've also tried a different freewheel and have the same problem.

It would seem to me that the only fix would be to expand the bearing bore but trying to sand that and keep it square is going to be a trick.

I contacted Paul and they said they'd never heard of this and never had a problem. So I'm trying to figure out what my options are to try and get these rideable. These aren't my only wheelsets so I'm not in a hurry to try and fix them.

Thanks for any ideas.

Mr. 66

That sounds like a horrible idea, unless you want to wreck the wheel. Your freewheel has no connection to the hub bearings. My first thought is on a flip flop both sides can be drive side. My second thought is your axel stack is not adjusted correctly, perhaps a cone or locknut is loose.

Mad Honk 

My experience with pre-load on the hub is to adjust the drive side first and then go to the non drive and adjust by moving the cone down to the bearings and the backing off by 1/4 turn. This should set the pre-load for the axle. Any issues for the freewheel are going to be different from this. HTH, MH

Andrew R Stewart 

It sure sounds like the FW being tight on the hub is also compressing the driveside bearing. I assume this hub has cartridge bearings? Correct? This condition is one indicator that the bearings are getting worn. Do know that most all hubs can't separate the drive side bearing preload from the non drive side's.

Worn cartridge bearings often feel fine when not compressed or under strain. I suggest replacing the hub's bearings, it costs little and in time will be needed anyways. Andy

FBinNY 

Taking an off the hip shot in the dark, the shell may be cracked in the thread area.

Keep in mind that because threads are basically 60 degree triangles, they do exert radial forces when bottomed out. You can draw yourself a quick sketch and see how this would work.

Normally (in a well designed hub) the bearing would be located inboard of this threaded area and insulated from any compression, OR the section between the bearing and threads is thick enough to handle any compression without compressing beyond the design allowance.

Regardless of the design, the fact that all has always been good means you need to focus on what might have changed, ie. a hairline crack in the shell.

Shinkers

These are indeed cartridge bearings and I've noticed this issue with brand new bearings. Everything feels fine until the freewheel is tightened. This is also with the axle removed from the hub completely. I can tighten the freewheel with a chain whip and the drive side bearing is noticeably tighter than before tightening (feels notchy).

FB, all has not always been good since these have always gone through bearings and I'm just now diving in to figure out why. This has also happened with two different hubs. Radial pressure from the threads is what I'm thinking.

jccaclimber

Is the inside of the freewheel designed in a way that rubs the bearing?
I’ve seen a rare freewheel where the last couple threads are undersized, putting a larger than usual squeeze on the hub.

Andrew R Stewart 

This issue is a good reminder why loose ball, cup and cone, bearings were so standard for so many decades. They can absorb the bearing compression with being adjustable in their preload. Cartridge bearings are really nice, till they aren't. Andy

Shinkers

I'm able to thread the freewheel on backwards so I don't think so.

I'm with you Andy. I've never had problems with loose ball hubs.

Pic of the bearing and its position in the threads.

oldbobcat

I'm speculating that the threaded section of the hub shell is so thin that loading of the freewheel against the shoulder is causing distortion of the shell, which is compressing the bearing. I've experienced this with some press-fit bottom brackets in some frames whose shells were a little on the tight side of spec.

FBinNY 

Yes, but not necessarily the result of radial compression, though as I pointed out earlier, that's possible.

Keep in mind that it's VERY difficult to produce large diameter threads with a helical axis congruent with the cylindrical axis of the shaft (or nut). This is what causes the common freewheel wobble. Normally, is shouldn't be an issue, but if the error is great enough it could cause the shell to deflect as the freewheel bottoms unevenly.

As I said, it's a design fault, involving a poorly located, overly sensitive bearing, and a shell not rigid enough for the task. It isn't readily fixable, though you might try your luck with other freewheels, hoping to find one with better thread alignment,

If you're interested enough, you might confirm by cleaning the threads and shoulder, and using die-marker. Tighten and back off the freewheel a few times and look for uneven wear.

Crankycrank

Welcome back Mr. FBinNY. Hope to see some more posts from you. Not giving up my Chain-L. They'll have to pry it from my cold, dead hands.

jccaclimber

I’m fishing at this point, but does it happen faster if you ride in the large rear sprocket vs. the small one?

Edit, I was thinking you had thrown an old multispeed freewheel on, not a single speed. That might result in a larger gear>more torque on the threads, but it sounds like that’s not the case.

FBinNY 

Hopefully, it won't come to that anytime soon.

Back to the OP's issue.

As I posted earlier, I suspect that it's more likely an angular deflection vs. radial compression. Radial bearings of this type are designed for some radial compressing resulting from interference fits. I'm not convinced that the radial load from the freewheel would be enough to damage the bearing.

It MIGHT help if an angular contact bearing is substituted for the original radial bearing. However, unless the design already provides for it, some creative modification of the axle would be needed to maintain axial pre-load.

Also consider that the type of "sealed" bearing typically used is intended for things like electric motors and has dust seals, not true weather seals. As such they are NOT waterproof, and out in the real world the seals do a better job keeping water in than out. So the real culprit may be corrosion, rather than load or wear. This is why many experienced mechanics, including myself, greatly prefer old fashioned systems that are forgiving by design and allow user service.