Would this BB be ok?
- Thread starter User16625
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Thats the answer I was hoping for. It explains why I am having trouble using it on my road bike (rideable, but creaky). It does not explain why the person at tredz assured me this was compatible with my road bike. As far as I can tell it is not even compatible with my MTB which uses a BB51. Where do I stand as far as refunds go?
This product is now second hand but it was not of the description I was told it was (compatible with my road bike basically). I even showed the guy my old BB. Had I known its compatibility then I would not have purchased it.
I like Skol
A Minging Manc...
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Actually I think your BB should be fine for the chainset if it is Hollowtech II specific.
I know the BB51 and BB70 are directly interchangeable as I have done this myself and they are dimensionally identical. The big problem with Hollowtech is getting the spacer set-up right and then making sure the preload is just enough to clamp the bearings and no more!
I think your bike probably has the right BB but it has been installed incorrectly, did you fit it or the shop?
The factory fit OEM Hollowtech BB on my hybrid didn't last long (between 2-3k) and the replacement I fitted also died prematurely at about the same distance. When fitting the 'better' BB70 I noticed that the factory fitted spacers were wrong and the left hand arm was actually bottoming out on the axle splines before loading the bearings. It was a slight gap but enough to shorten the life of the bearings. I added a thin shim behind the left hand bearing and the set up has run perfectly since and has done between 3-4k at the moment. I suspect you need to strip out your new BB and check the installation has been done correctly.
I could be wrong but I am reasonably confident in my belief that any Hollowtech II bearings will fit any Hollowtech II specific chainset.
I know the BB51 and BB70 are directly interchangeable as I have done this myself and they are dimensionally identical. The big problem with Hollowtech is getting the spacer set-up right and then making sure the preload is just enough to clamp the bearings and no more!
I think your bike probably has the right BB but it has been installed incorrectly, did you fit it or the shop?
The factory fit OEM Hollowtech BB on my hybrid didn't last long (between 2-3k) and the replacement I fitted also died prematurely at about the same distance. When fitting the 'better' BB70 I noticed that the factory fitted spacers were wrong and the left hand arm was actually bottoming out on the axle splines before loading the bearings. It was a slight gap but enough to shorten the life of the bearings. I added a thin shim behind the left hand bearing and the set up has run perfectly since and has done between 3-4k at the moment. I suspect you need to strip out your new BB and check the installation has been done correctly.
I could be wrong but I am reasonably confident in my belief that any Hollowtech II bearings will fit any Hollowtech II specific chainset.
Its just that I only started having problems since I have installed this new BB. I tried different spacer combinations but it doesnt work. I have replaced these BBs in the past without trouble. Im convinced by the fact that it says " XT M770 / SLX M660" on the packaging and not "FC 4600" like it says on my road bike crank.
I like Skol
A Minging Manc...
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- Sunny Ashton-under-Lyne
Have you sat them side by side on a flat surface? It should be quite obvious if they are different.
oldroadman
Veteran
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- Ubique
Just to revisit your original question - why would you want to do that? Unless you have been wrongly supplied with parts, as earlier posts possibly indicate.
I like Skol
A Minging Manc...
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- Sunny Ashton-under-Lyne
The idea of group specific componentry is encouraged by Shimano to maintain the separation of various 'qualities' of groupsets and has nothing to do with the mechanical fit of the parts. Just as you can mix and match MTB and road cassettes between disciplines and across groupsets I also suspect the BBs will be the same. The BB shell in the frame is a set width for road and MTB so there is no reason for the BB cups to be different. All you need to ensure is that the correct spacers are used to achieve the same overall width across the BB cups (the external dimension). Having said that, as in my case, there is no guarantee this was set right in the first place!
If you go to a supplier for a hollowtech BB for your road bike there should be no need to leave empty handed just because they only have the MTB version in stock.
I like Skol
A Minging Manc...
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- Sunny Ashton-under-Lyne
Just had a look at the Shimano techdoc and I still can't see anything to suggest that all Hollowtech II BBs are not interchangeable.
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
Then it should work just fine with the MTB ones then as the splines on the axle will accommodate the extra 2mm or the cups can be installed using thinner shims?
I like Skol
A Minging Manc...
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- Sunny Ashton-under-Lyne
??? You said MTB cups are 1mm wider than the road equivalent. This means he should be short of axle length, not the other way round.I refer you to my original post...
