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What type of bottom bracket is this?

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What type of bottom bracket is this?

Old 04-24-20, 12:17 PM
  #1  
phivos
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What type of bottom bracket is this?

Just replaced my lovely aluminum frame MTB with a used carbon fiber road bike. I thought this was going to be an upgrade, but ended up being a disaster!
The bike appeared to be in good shape, but after a few miles on the road, I realized that the BB shell was spinning inside the frame as I was pedaling. I also noticed a slight play of the crank set.
After taking it apart, it was clear that the BB shell is an aluminum cylinder. Should I say an "insert", I don't know. You can easily spin this inside the carbon frame, but impossible to remove by sliding out. So this is not a press fit. I'm trying to figure out if it is possible to remove so I can properly fix this. There is a groove inside the aluminum shell (apart from the 2 grooves used for the bearing retainers). This may be a sign that the shell was made out of 2 pieces (left and right) either threaded together or press fitted. I've attached a couple of photos in case someone can identify this and help me out.
The bike is a BH Prisma with Shimano 105. The crank shaft has a diameter of 24mm.
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Old 04-24-20, 05:58 PM
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Most likely the Al sleeve was bonded in place, carbon makes for a poor press fit (hence all those creaking issues with them). There might be a OD change along the sleeve and if the bonding broke down that OD steps might be hanging up on the old adhesive.

The use of an AL sleeve is actually a good design as it far better is machined to accept a press fir bearing and tends to not wear/change it's bore over time. But they can come loose when the bonding isn't done right. I have no advise but would suggest seeking a carbon frame repair business, Calfee is one. Andy
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Old 04-24-20, 07:52 PM
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Ruckus Composites does this: https://ruckuscomp.com/news/tag/bottombracket
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Old 04-24-20, 11:56 PM
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Originally Posted by Jeff Wills
Ruckus Composites does this:
Originally Posted by Andrew R Stewart
Most likely the Al sleeve was bonded in place, carbon makes for a poor press fit (hence all those creaking issues with them). There might be a OD change along the sleeve and if the bonding broke down that OD steps might be hanging up on the old adhesive.

The use of an AL sleeve is actually a good design as it far better is machined to accept a press fir bearing and tends to not wear/change it's bore over time. But they can come loose when the bonding isn't done right. I have no advise but would suggest seeking a carbon frame repair business, Calfee is one. Andy
Thanks Andrew and Jeff for your prompt response. I'll try and get the bike to a specialist for this kind of work. Under the COVID circumstances it's not that easy to move around! Thanks again.
P.S. I couldn't find the like button...both of you really deserve this!
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Old 04-25-20, 10:23 PM
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"Like" button in the bottom bar, far right.
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Old 04-26-20, 08:45 AM
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Originally Posted by Jeff Wills
"Like" button in the bottom bar, far right.
I still cannot find it! Is it possible that it doesn't exist for me ....being a newbie?
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Old 04-26-20, 10:10 PM
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Originally Posted by phivos
I still cannot find it! Is it possible that it doesn't exist for me ....being a newbie?
Could be. I've only been on Bike Forums for (eek!) 12 years.
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Old 04-26-20, 10:14 PM
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Originally Posted by phivos
Thanks Andrew and Jeff for your prompt response. I'll try and get the bike to a specialist for this kind of work. Under the COVID circumstances it's not that easy to move around! Thanks again.
P.S. I couldn't find the like button...both of you really deserve this!
If you're using the Mobile version of the site, it's the button with a "thumbs up" icon, looks like this:
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