Replacing Hollowtech II Bearings

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SimonCelsa
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Re: Replacing Hollowtech II Bearings

Post by SimonCelsa »

Aaaah OK, all makes sense, thanks for the reply, will try the 7mm when the current ones give up the ghost.
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

SimonCelsa wrote: 28 Nov 2022, 5:37pm
zenitb wrote: 28 Nov 2022, 12:24am

....... - you could only get standard 25 x 37 x 7mm ones - these didnt fit (although Brucey did try and work out a way of getting them in). However the correct size 25 x 37 x 6mm bearings ARE now available - according to eBay - at about a fiver a pair.

I see your image of the eBay fiver a pair bottom bracket bearings zenitb but I can't see anything cheaper than £7.50 on my eBay search. Could you elaborate a bit, maybe advise who is the seller so I can improve my search, everyone likes a bargain!


Cheers, Simon
Ah yes, sorry I didn't post the link Simon. Generally I try and post links that will endure over time so future readers of the thread can see the item. I actually searched for "25 x 37 x 6" which seems to get multiple (cheap!!) hits!!

Try this

https://www.ebay.co.uk/itm/195191370811 ... media=COPY

Or this

https://www.ebay.co.uk/itm/394108248405 ... media=COPY
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SimonCelsa
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Re: Replacing Hollowtech II Bearings

Post by SimonCelsa »

That's good, thanks for that, Cheers!
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

boblo wrote: 28 Nov 2022, 5:43pm
Apologies for querying your post here boblo, but are you saying that the 25 x 37 x 7 mm is the correct bearing as opposed to the 25 x 37 x 6 mm item??
Either will do. If you're using the plastic top hat, the 6mm thick bearing will be just below the surface/rim of the HT2 cups and the plastic top hat will be almost flush with it. The 7mm thick bearing option would mean the plastic top hat will be a little proud of the HT2 cup but there's plenty of room for it between the cups and the crank arms so no issue either way.

I've never bought 6mm thick bearings, always 7mm and now I buy 24x37x7 to avoid using the fragile plastic top hats.
Interesting post Boblo. The only thing knawing at the back of my mind with this is something I thought Hambini said on one of his videos. I cant find this video now of course so I COULD VERY WELL BE WRONG, but wasnt the plastic liner in the Shimano Hollowtech patent a way of compensating for bottom bracket threads that are very slightly out of alignment axially ? I thought the fact they cant copy this patented feature was one of the reasons the SRAM BBs reviewed by Hambini end up with witness marks from under-rotation on the bearings on the BB axle itself, in poorly made frames (which seems to be the majority Hambini reviews)? That said if it all works for you (quality frame - no witness marks on the axle etc) then all is good but it might be worth monitoring this aspect in case of issues. In the meantime I will try and dredge out the Hambini video/quote....

All this HT2 stuff is new to me though.. so take this with a massive pinch of salt .. I could well have misunderstood it.
boblo
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Re: Replacing Hollowtech II Bearings

Post by boblo »

@zenitb Thanks for that and all that may well be true. I don't listen to Hambini these days as I find a sweary bloke in his garage lacks a bit of cred. If he was such a high falootin engineer, 'they'd' be beating his door down and he'd probly look a lot more successful. Not saying he's wrong, just that he lacks a bit of cred IMO.

The top hat can't be that crucial as it's not supplied with the newer style Shimano HT BB. I'm not sure when they changed the design but the tool interface on the cups of the older one are bigger in OD and have the top hat, the newer one's cups have a smaller OD (the installation tool is/was supplied with the BB and fits into the earlier versions tool when used) and doesn't use the top hat.

Not sure what that tells us about frames but I've both old and new HT2, GXP and a couple of those BB30 to HT2 converters (to stop the infernal creaking) and they're all OK apart from lasting about as long as a Rizla in a rainstorm... Square taper on the other hand... :D
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

boblo wrote: 28 Nov 2022, 9:12pm ..
The top hat can't be that crucial as it's not supplied with the newer style Shimano HT BB. I'm not sure when they changed the design but the tool interface on the cups of the older one are bigger in OD and have the top hat, the newer one's cups have a smaller OD (the installation tool is/was supplied with the BB and fits into the earlier versions tool when used) and doesn't use the top hat.
...
that sounds interesting Boblo .. certainly having more diameter to play with in the sealed bearing will have the advantage of "bigger balls" :-) and this might help with longevity more than any theoretical advantage the plastic top hat might have.

I do like the general idea of replacing the bearings rather than chucking the whole unit away .. and it great to hear people are already doing it. Next time it fails I will give it a shot.. maybe even trying the different approaches here to see what works best. I guess this thread will still exist then so we can always post back any experiences, good or bad.

cheers

George (aka zenitb)
Cyclewala
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Re: Replacing Hollowtech II Bearings

Post by Cyclewala »

How easy is it to prise the old bearings out? And is a press tool required for the new ones?

When I commuted (5k mls/yr) I was going through 2 BBs a year. Once I moved to a more water resistance grease and created a grease lip as described by Brucey, this improved to one BB a year.

His post on page 1:

“ The shimano bearings have a single seal mounted in the inner face of the bearing and a separate external seal. The external seal appears to fail and let the water in. The seal can only work (and not wear) if the seal lip is wetted with lubricant, so it isn't a bad idea to spray some lube (e.g. semi-fluid spray grease) in the little gap from time to time.

If refitting bearings to cups, I think it makes sense to fit both seals on the outside, and to whack as much grease as possible inside the BB housing between the (now open at the rear) bearings.”
boblo
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Re: Replacing Hollowtech II Bearings

Post by boblo »

How easy is it to prise the old bearings out? And is a press tool required for the new ones?
Short version: very.

I used an old steel rod as a drift to remove and a block of wood/hammer to install for years and years and years.

I recently 'upgraded' to an eBay £15 cycle specific bearing extractor and a cheap press. Total £25. It feels a bit less medieval now but I've not broken/bent or otherwise trashed anything before either. Mebbies lucky.

This is the extractor: https://www.ebay.co.uk/itm/132932948694 ... 3056127387
gxaustin
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Re: Replacing Hollowtech II Bearings

Post by gxaustin »

Big T wrote: 15 Sep 2013, 9:04pm Cut your losses now and go for a square taper chainset. You can get a reasonable one for £60-70 and the BB will last 15,000 miles.
My bike has done at least 36,000 miles and I changed the push in BB at about 16,000 miles. This is a standard Shimano BB.
gregoryoftours
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Re: Replacing Hollowtech II Bearings

Post by gregoryoftours »

tim-b wrote: 28 Nov 2022, 6:32am
This leads to my first question. Is there a reason that the NDS gets worn out first?
IMHO it's because the NDS isn't protected in the same same way as the DS. The DS has a lump of aluminium that stops water running down the crank from the pedals and rider and along the axle. The same lump effectively shields the bearing from external weather as well.
Anecdotally, a rubber o-ring on the NDS crank diverts water off the crank in the same way as a window sill drip groove works, I haven't tried one on the NDS axle
Ht2 cranks have a rubber seal on both inward faces that helps to prevent water getting in between the plastic top hat shields and the spindle. If agree that the NDS side usually goes because it's more exposed.

To the OP, the Shimano BB that you have there is way shorter lived than the next spec up. It's worth spending the extra money for an xt/ultegra BBMT800 / BBR60. They last much, much longer my experience. Get one of these and then replace the bearings when they go.
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

gregoryoftours wrote: 2 Dec 2022, 1:02pm

To the OP, the Shimano BB that you have there is way shorter lived than the next spec up. It's worth spending the extra money for an xt/ultegra BBMT800 / BBR60. They last much, much longer my experience. Get one of these and then replace the bearings when they go.
Thanks Gregory...interesting info ..do you know if it uses the same removal tool as my Tiagra one? Or does it get its superior durability by being a wider diameter?
Attachments
BBR60
BBR60
Jules59
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Re: Replacing Hollowtech II Bearings

Post by Jules59 »

My Dolan ADX has an Ultegra groupset with a Hollowtech II crank and a press-fit BB72 bottom bracket. I think its the BB72-41B
Are the bearings inside this BB the same as the threaded Ultegra BB as mentioned above and is my BB likely to suffer the premature wear - all things being equal ?
The Shimano BB72-41B is not very expensive and my BB is fine at the moment but thinking ahead I wonder if there is an alternative press-fit BB that might last longer than Shimano.
gregoryoftours
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Re: Replacing Hollowtech II Bearings

Post by gregoryoftours »

zenitb wrote: 5 Dec 2022, 12:33pm
gregoryoftours wrote: 2 Dec 2022, 1:02pm

To the OP, the Shimano BB that you have there is way shorter lived than the next spec up. It's worth spending the extra money for an xt/ultegra BBMT800 / BBR60. They last much, much longer my experience. Get one of these and then replace the bearings when they go.
Thanks Gregory...interesting info ..do you know if it uses the same removal tool as my Tiagra one? Or does it get its superior durability by being a wider diameter?
It's actually a smaller diameter than the lower spec models. I think that it must be sealed better. No BB should go as fast as some of the silver Shimano ht2 BB s that I have seen, but they're always full of rust when they go so I think that the problem is with the sealing rather than bearing size. The 105/ultegra usually comes with a plastic adapter tool that fits into a 'normal' ht2 tool.

Having your Frame bb shell faced is a good idea for external BBs because they are 2 separate halves so need to line up exactly, unlike square taper/octalink cartridge BBs.
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

gregoryoftours wrote: 5 Dec 2022, 8:08pm
zenitb wrote: 5 Dec 2022, 12:33pm
gregoryoftours wrote: 2 Dec 2022, 1:02pm

To the OP, the Shimano BB that you have there is way shorter lived than the next spec up. It's worth spending the extra money for an xt/ultegra BBMT800 / BBR60. They last much, much longer my experience. Get one of these and then replace the bearings when they go.
Thanks Gregory...interesting info ..do you know if it uses the same removal tool as my Tiagra one? Or does it get its superior durability by being a wider diameter?
It's actually a smaller diameter than the lower spec models. I think that it must be sealed better. No BB should go as fast as some of the silver Shimano ht2 BB s that I have seen, but they're always full of rust when they go so I think that the problem is with the sealing rather than bearing size. The 105/ultegra usually comes with a plastic adapter tool that fits into a 'normal' ht2 tool.

Having your Frame bb shell faced is a good idea for external BBs because they are 2 separate halves so need to line up exactly, unlike square taper/octalink cartridge BBs.
Thanks Gregory.. I was unaware of all this but it perhaps explains why my tool didnt fit my brother-in-laws BB on his posher bike. Found it now.
Attachments
105 is only slightly narrower than Tigra .. classic Shimano!!
105 is only slightly narrower than Tigra .. classic Shimano!!
Adaptor Installation Tool TL-FC24 from front
Adaptor Installation Tool TL-FC24 from front
zenitb
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Re: Replacing Hollowtech II Bearings

Post by zenitb »

Jules59 wrote: 5 Dec 2022, 6:56pm My Dolan ADX has an Ultegra groupset with a Hollowtech II crank and a press-fit BB72 bottom bracket. I think its the BB72-41B
Are the bearings inside this BB the same as the threaded Ultegra BB as mentioned above and is my BB likely to suffer the premature wear - all things being equal ?
The Shimano BB72-41B is not very expensive and my BB is fine at the moment but thinking ahead I wonder if there is an alternative press-fit BB that might last longer than Shimano.
maybe do what we have done above Jules. Wait until it wears out, fit another genuine Shimano one in the meantime, and then carefully take apart the worn one so you can see what size sealed bearings it uses. Then order high quality replacement bearings from FAG or NTN - or whatever quality level you prefer?
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