Front hub failure

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Lurkin

100 kW
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Jan 18, 2015
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Melbourne, VIC, AUS
My commuter bike (Trek X-Caliber, BBS01 250w, Dolphin pack battery) has a Shimano HB-RM66 Cup and Cone hub on the front. Its a very basic hub, just what came with the bike.

Late last week, the hub was making a few scrappy sounds. I disassembled, greased with Shimano Premium grease generously and reassembled. The 'cap' appeared to be pitted, so I used a rounded piece of steel and hammer to knock it back into a circular shape. The seal in between the cone and this cap was damaged. The cap was goobed with clean grease, the bearings were dry as bones as what was the cup and cone. I have disassembled and re greased this previously, the greasing was very generous. Anyway, the plan was to ride on this until I have acquired a cap and replace it could never end up the same as new.

I rode 80km on Monday, and another 40km to work on it yesterday fine. Upon leaving work yesterday, there was decent 'cronk' sound and it appears the hub has completely given way, i.e. the cap part connected to the cone was off and the bearings were spilling out. I will take it apart in the weekend to inspect.

The cap in the diagram below is connected to the hub itself (has Malaysia written on it) and appears to be a press fit to the hub.

Diagram: https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwihuI-I-_jLAhUCmpQKHePNBV0QFgggMAE&url=http%3A%2F%2Fsi.shimano.com%2Fphp%2Fdownload.php%3Ffile%3Dpdf%2Fev%2FEV-HB-RM66-3254.pdf&usg=AFQjCNEegPSmUqu86WlMZNNSqxSflBqysg&sig2=S2PZKCcl_ZgO-C9jmF7P8w&cad=rja

A couple of things to ponder from this:-
- Using bike parts as ebike parts could be putting increased stress on the hub. Could this have lead to premature failure?
- Are cup and cone bearings the best for an ebike or is a cartridge style better?
- The wheels are 29er. Could the increased wheel side also stress the hub differently?

The ultimate question is: is it worth trying to get another identical hub (so the wheel rebuild is easy) or is it worth switching to something else?
 
Cup and cone take side loads better, so in theory, would be better for a large wheel like a 29er. But in reality, It makes no difference.

Cartridge bearings are no maintenance and disposable. stick a new one in the hole, re-attach the wheel, ride. Cone bearings can last for generations, but require regular maintenance. they also take some skill to set up properly, and that means more time spent servicing them.

Both styles are likely to out live the rest of the bike or it's rider. Neither has any rolling advantage. Cartridge using hubs could have a weight advantage of a few grams, but only if the hub is specifically built for it. They aren't usually lighter. Cup and cone are field serviceable, and extremely fault tolerant. I had a friend once ride home on some greased up shoe leather packed into the cup when his bearings failed far from home.
 
Nelson37 said:
Cup and Cone largely being phased out in favor of cartridge, and likely will not be available, for the most part, in the fairly near future, if not already.

Much easier installation and replacement for cartridge, if nothing else.
Click to expand...

Both the above statements are mistaken.

I personally prefer cartridge bearing hubs in most circumstances, but cup and cone bearings are here to stay. They're stronger for any given size, usually easier to service with simple tooling, and better configured for the load characteristics of bicycle wheels. They can be effectively shielded with non-contact seals, making them essentially drag-free. At the practical end of the market, satisfactory cup and cone hubs can be made much more cheaply than cartridge bearing hubs (more cheaply than just the cartridge bearings), so they're unbeatable for cost effectiveness.

As for the OP's issue, I have a couple of observations: once a bearing starts to fail, the damaged elements must be replaced. Otherwise, the failure continues to progress even if the bearing is cleaned and greased. For a cup and cone hub, that usually means replacing the cones and balls in the hub.

Too much bearing preload is the primary cause of total failure in hub bearings. This can be from cones that are overtightened before installation, or from cones that become overtightened when the QR skewer is secured. QR hubs must be left slightly loose such that they become correctly tightened upon installation.

Analogously, cartridge bearings should never be subjected to static axial preload at all. It's much healthier for cartridge bearing hubs to exhibit a small amount of side play than for them to take up the play in their bearings by preloading them.
 
Hmm. I've ordered another hub that's exactly the same to completely replace it given its highly likely to be quite damaged now.

Using the same has the advantage of using the same spokes and rim due to not change in hub flange sizing (fingers crossed there's been no design update).

Cup and cone again it is then. I will Google around before paying with it again, but the trickiness in setting these hubs up relates only to the amount of play/set up of the cone and nut locking against it with wheel spanners I take it? If so, what is the right amount if play/correct proceed to maintain max hub life?

I plan to open up and put more grease into the replacement hub on arrival as I've read they can be a bit on the dry side. Again, what is the best amount of grease to have in there? This hub has two plastic seals on the cone and I don't want to overdo it and damage them as I think it was a key contributor to the original failure.

And... what grease to use? I was planning on using Shimano premium grease,but I'm not sure it's the correct grease (seems to be too thin). Elsewhere I've read recommendations for Morley Waterproof grease or Castrol marine type greases. Most of the threads I've read lack any scientific testing and most devolve to "any grease is better than none" which is just an obvious fact which doesn't really help. Any thoughts on that? The bike specific greases seem expensive and lack information (I. E. Just marketing buzz) so it's pretty tempting to shift to an industrial product instead.
 
Oh and many have said cup and cone are more maintenance, but how often is that? The bike does 400km+ of commuting per week... don't really want to pull these apart any more than I need to....
 
How often you need to do your cup and cone hubs depends on mileage, load, weather conditions, effectiveness of the seals, characteristics of your local filth, and how well they were lubricated and adjusted to begin with. Some hubs hold up better than others; the most traditional designs tend to have the best longevity.

The median interval between required hub overhauls in my area is a few years, even for bikes that are used daily. BSOs tend to eat their hubs up in months or less if they're ridden daily. Folks who ride indiscriminately in all weather also have shortened intervals between hub service.
 
Ok, given the amount of use, three monthly will probably be the go.

Is the main issue the setting the correct amount of play with cup and cone?
What is the recommended amount of grease to put in there (ish)?
What grease is (usually) best?
 
Lurkin said:
Ok, given the amount of use, three monthly will probably be the go.
Click to expand...

I've never seen a hub that needed nearly that much attention unless it was submerged, but at least too much maintenance beats not enough maintenance.

Is the main issue the setting the correct amount of play with cup and cone?
Click to expand...

That's a critical issue if it's too loose or, especially, too tight. Start with a little bit of play that goes away when you do up the quick release skewer correctly, through 90 degrees of resistance.

What is the recommended amount of grease to put in there (ish)?
What grease is (usually) best?
Click to expand...

Use lots of grease. Put in enough that a little bit squishes out when you assemble the cones.

Anything waterproof will do. For my own use, I like greases that are fortified with MoS2 (e.g. Valvoline Synthetic grease), but those are black. Other mechanics prefer a white or brightly colored grease that serves as an indicator of contamination, but most white lithium greases turn into tenacious adhesives eventually (after a decade or more). At my shop we use Lucas Red 'n Tacky #2, which has excellent lubricity, cohesion, and high temperature characteristics (good for coaster brakes and Rollerbrakes). Most other bike shop greases are not red, so it can help with forensics and troubleshooting too. ("Did we do this?")
 
Two bike shops have listed them online but bailed on me once I've gone through with the purchase of a direct replacement, so I've had a look at the compatibility options on Shimano's website.

HB-m615 looks to have the closest similar spec, with a 0.2mm different in offset and a more complex seal arrangement being the only identifiable differences. I'm assuming the minor offset change is insignificant. The seal on the old hub is contact, new is contact and labyrinth. Would this be an improvement (seal change)?

I've been watching youtube and I've seen other manufacturers (WTB) have grease nipples on their hubs and one way seals, so the servicing entails forcing grease through the nipple, which in turn forces out the old grease and rubbish and replaces it all with new fresh grease. Any thoughts on whether these are worth investigating further? Being able to service it without disassembly is a pretty attractive option/feature.
 
WTB has offered hubs with grease fittings since the 1980s; in my observation only a small percentage of them were ever maintained by that means. They are otherwise pretty normal hubs, so they respond to ordinary maintenance in an ordinary way. The ones I remember had cartridge bearings with seals only in the outer side, so you could always swap out the bearings if grease purging didn't do the job.

If you like the idea of grease purging, and you're diligent about refreshing the grease before there's a problem, then WTB Grease Guard hubs might be a good option for you.
 
Continued to look at WTB, but only option that confirmed being grease guard (has the nipples) and shipping to Aus was AUD80 (~USD61) which is beyond what I want to spend on an experiment/commute bike. I've ordered a HB-M615 from Japan, should be here ~25th of April.

Disassembled the damaged hub today. Looks as if the damaged plastic seal had torn apart and snuck beside the bearings, forcing the cap (dust cap?) out of the hub. Given that the cap was damaged before, its rooted now. It has bearing imprints in it where a couple were jammed. Its all very strange, its like the cone had jammed on the cap, which had lead to thinking the cones were tight, which when the cap shifted they were no longer and hence it cap came off and everything was loose. Whatever, the point is the seal and cap were damaged and lead to the failure. The cap had been taking the weight and grinding its insides against the outer edge of the cone (where the spanner goes, not the bearings). So its completely lunched the seal and cap but the cone, cup and bearings are fine.

Upon removing both, reinserting the bearings with grease and just the cone, the hub would happily spin as it had prior to the failure. Slight, tiny bit of vibration, but nothing untoward. Zero play laterally, basically perfect. So that got me thinking - if the cup holds the bearings with the support of the cone, then the cap and seal are actually required (only for longevity, which I'm not concerned with as there's a totally new one on the way). I've really, really packed the grease in with the bearings, then filled all the way to the end of the hub and covered with a pringles top (with a hole to match the seal cut out to pin it there), cable tied to the spokes and similarly supported in place with a nylon spacer and further cable tie. Not ideal, but should hold until the replacement arrives, has much more capacity for grease and has the advantage of being viewable... maybe its a product improvement :lol:

Can anyone confirm the cap is a "dust cap" and definitely does not support/touch the bearings directly normally? If so, this macgyver, temporary set up should be ok until the replacement arrives:

Destroyed seal:
20160409_135910_zpszuqdu9cu.jpg


Destoryed cap:
20160409_135906_zps8ovuzqjj.jpg


Macgyver temporary cap using a pringles top, cable ties, spacer and a shedload of junk/free lithium grease (Morley's Red Waterproof grease on the way for future bearings as its a localish, highly recommended industrial grease, just using lithium for pigment and because I want to get rid of it on this):
20160409_135855_zpsnhpl71eu.jpg


It has already survived a test ride of ~10kms so theres hope 8)
 
Cool, yep I'm thinking you'll be fine and those were just 'dust' caps.

Bearings have races. The big one is technically the 'outer' race, which is usually integral to the hub. The small one is considered 'inner race', and it's the cone that threads on axle. All there is to it afaik. Some of the ones I've seen have various seals for dust/moisture, but that's all they're for.

Definitely an unordinary failure with that hub, especially if the bearings and races turned out to be fine. I imagine you have a parts bin, so upon hub replacement the good cones, bearings, nuts, washers, and seals could be added for spares. In fact, you may just want to consider swapping the axle from new hub to save from rebuilding the whole wheel.
 
Hmm. I'm in a state of debate of the importance of this 'dust cap'. Assuming its not structural, then it doesn't make any sense to use decent steel to make it, as Shimano have. If its not structural, it would make more sense to make it from hard plastic - lighter and less likely to deform in the event of being struck. Ive half a mind to either buy or access a 3d printer and just print one to make a neater job of this and just leave it be.

Alternatively, it has nothing to do with bearing support and everything to do with increasing the structural rigidity of the hub itself and solid protection of the balls when going through rough stuff. For those doing XXtreemeee off roading, this is likely to become an issue - for my purposes its unlikely to become a problem. The pringles cap works well even in the rain - the inner of the cap was not wet at all, despite riding through a decent downpour.

The new hub will be available in any case when it arrives. Couldn't get one the same for reasonable $$, so it will be an upgrade to Deore. Advantage being that it will not only have a contact seal, it will also have a labyrinth seal as well.
 
So for a ghetto roadside fix, this has held up surprisingly well which is fortunate given I haven't had time to build a new wheel. It's still going strong with the pringles cap fix... even though I have a brand new spare hub sitting in the parts box now, I think I'll just keep riding on it to see how far I can get before it completely gives out.
 
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