Bikeninja87

Hi,

I was hoping to find out if anyone has successfully repaired a bearing cup on a hub? Specifically a rear free hub if this helps. I took apart the hub and found that one side was fine, caged bearings as they should be but the other side had a completely mashed cage and dust cover. The bearing cup inside has been damaged a little.

I was told by a friend that it would be fine to just replace the caged bearings and put plenty of grease in but I'm not sure if I should try some chemical metal (Loctite or alternative) to seal up any pitted areas prior to replacing these parts. any ideas?......

dsbrantjr

I would replace the balls (a cage is not needed) and see how it goes; no adhesive will give satisfactory results, nor will trying to polish out the pits AFAIK.

SkyDog75

There's no practical way to repair pitted cups. Anything you fill the pits with is bound to be softer than the hardened steel the cups and balls are made of, and it'll get ground out in short order. Then it'll just be contaminating your grease and acting as an abrasive.

If you're not going to replace the hub ASAP, grease it up and ride it 'till it gets bad enough you need to replace it. It might take a while.

xenologer

I've heard, that a strategy is less-than-first world countries
is to pack the damaged hub with abrasive compound and new balls.
ride it a while
then completely clean everything out and repack with grease and new balls

idea being that it regrinds the damaged cups and cones

Racing Dan

Clean it out, replace the balls and lube well with grease. Unless cup and cone is excessively pitted you'll be fine. I have ridden many miles on wheels with (lightly) pitted cups and haven't noticed any ill effects besides a slightly notchy feeling when turning the axle by hand.

dabac

At least Shimano has shown a surprisingly little imagination and used the same size bearing cup in many hubs. So if you find a donor hub it's possible to knock the cup out and transplant it to the keeper hub.

JohnDThompson 

That's a way to polish (or re-polish) the races, but if they are damaged to the degree that pits extend through the case-hardening, it won't help.

IthaDan 

I've had DECENT luck with pitted hubs by either adding or deleting a single ball (or removing the cage and using the same number of balls the cage called for) from the bearing assembly of the pitted side. My thinking was that adding or deleting a ball would have the balls running in a different "track" than before, potentially missing the pit as they travel around the race. Similarly, bearing balls a size larger can work DECENTLY, for a decently long amount of time in a pinch.

I've never paid enough attention (it's been a while since I was head wrench at the local co-op) to note if this has a large enough impact on the OLD of the hub or the dish of the wheel to matter.

Brittney

I guess it depends on how pitted it is. I have had cages grind up on the cone damaging the cone, cleaned it out, loads of grease and ridden for aged again on that wheel.

This is a [blurry] pic of how pitted the cone looked after cleaning up

AlexCyclistRoch

An old trick is to use automotive molybdenum grease. Molybdenum is a very soft metal, and it will deposit in the pits, making the bearing smooth again. On the downside, it's thick and slow...

mtnbke

Cup/cone hubs should be considered disposable. Every mile on a cup/cone hub is a less efficient mile than the previous one if you can't replace the inner race.
Ñ
Sealed bearing hubs can be returned to like new every time you replace the bearings. The problem with cup/cone bearings is the pitting and galling on the inner race projects into even upgrade super hard ceramic balls and then ultimately the cup (outer race).

xenologer

on the other hand, [cartridge] bearings ("sealed" can refer to cup/cone as well btw, if they have seals on them)
being self contained units must use smaller bearings, which can often have a much shorter lifespan compared to a good quality, well maintained cup/cone type.
So while they're easier to replace, you'll be spending $$ doing it more often.

I also tend to see a lot of 'boutique' hubs using a poor choice of cartridge bearing -ie symmetrical deep groove bearings when angular contact bearings are more appropriate to a hub application

Racing Dan

Cup and cone is perfectly fine. If they see a bit of maintenance, say once a year or every other year, they will last longer than the rest of the wheel. That goes for cartridge bearings too. No need to ever replace unless they are made of Chinese "cheese" or never see any maintenance.

davidad

Where does this idea come from? I have hubs with over 60k miles on them and they run fine. The loads and speeds are not anywhere high enough to make a difference in a properly maintained angular contact bearing.

xenologer

From Marketing:
cartridge bearings cost more
so they must be better, right?

xenologer

This was incorrect advice.

People shouldn't just assume they know. Reminds me of Old Potatoe offering his expert opinion on what taper Mavic bottom brackets were. Then when challenged becoming adamant that he knew. He just thought he knew and he was wrong.

AnkleWork

That's just the [il]logical extension of the "replace the balls regardless of condition because they're cheap" philosophy.

Bikeninja87

Hi everyone,

Thanks for all the advice. I have now re-packed with loose bearings and grease. I think I may plan to upgrade my wheels anyway as the last time I took everything apart I noticed a lot of dings on my wheel rims which needed sanding out as I had been getting a lot of punctures.

Bike Gremlin

Have you tried this with success? For all I know, in order to form a protective layer, molybdenum (grease) needs higher pressure that appears in a bicycle hub.

AlexCyclistRoch

It's worked fine for decades on cars, and I doubt that most car wheel bearings put any more force on the races than a bike does. Yes, I have done this with 'degraded' cones, and if not too bad, they work fine.

Bike Gremlin

I've re-packed pitted bearings with fresh grease and new balls, but never tried the moly grease thing. After you lube with molybdenum grease, ride for a while, do you later switch back to "ordinary" grease? Do the races look better, with pitting filled by molybdenum disulfide?

For all I know cars put a lot more load on their bearings than bicycles do. Even there, for wheel bearings, I didn't know there's enough load for molybdenum to form a protective layer.

dabac

Huh?


Are you saying you think that you're getting punctures b/c of the rim being dinged, and that sanding the rim would prevent that?


A dinged/dented rim might be related to a puncture IF the puncture is a pinch flat.
But sanding the ding is hugely unlikely to do squat for avoiding future flats.
Running higher pressures, switching to wider tires is more likely to help with that.

Metaluna

I don't know much about its properties, but I do know that "black moly" grease is used pretty commonly in other low-stress metal-on-metal applications, especially cameras and optics, e.g. lens focusing helicoids, shutter escapements, mirror pivots, etc., including being spec'ed by the manufacturer. I assume Nikon, Leica, et al. know a thing or two about lubricants, however MoSO2 is only one component of the formulation, and that might make all the difference. The other thing is that, for a lens helicoid, you have threads that are machined to very tight tolerances and are in close contact over a very long linear extent, and which have to slide against each other with silky smoothness. Not really the same environment as a wheel bearing.

Bike Gremlin

For all I know, moly is added for extreme pressures and loads resistance. Usually recommended for sliding connections with higher loads and pressures. I have some doubts that it could cure a pitted roller bearing. Though, like they say - a man learns for as long as he lives - and still dies stupid.

fietsbob

Cup is in the hub.. few* are removable, the right side of a cassette wheel the whole driver can be replaced.

*Old Campag record hubs had replaceable cups. good luck finding those repair parts at this late date..

cones can be replaced, for super rare stuff,

Aaron Goss in Seattle showed a shop trick with (ideally) a lathe and a die grinder..

or a variable spreed pair of drills .. 1 rotates the cone on an axle, the other rotates the die grinder stone..

taking the surface down to the level of the lowest point of the damage..




....