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Loose BB in carbon frame

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Loose BB in carbon frame

Old 03-28-21, 12:11 PM
  #1  
tombell
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Loose BB in carbon frame

Hi all
I have an issue with my carbon frame. I have the shimano R9100 bottom bracket.
I had some creaks which I narrowed down to the bottom bracket. I removed the drive side cup and moved to remove the non drive side one.
However, when I tried to unscrew it, the cup was turning but without unscrewing
I then went over one the drive side and screwed it back on. As I tried tighten it, I saw that it too started having the same behavior (turning without screwing) and at the same time
I noticed that as I was turning the drive side cup, the non drive side cup was also turning.
I am pretty sure that the BB shell has become unstuck. I cannot explain it any other way.

Now, I have 2 questions
1.The 2 cups thread in opposite directions, If I find a 2nd BB tool and use it to stop the shell from moving, I believe I will be able to remove both cups, by using the 2nd tool and applying opposite force.
I believe the shell is turning after applying a specific amount of force, so it is not completely unstuck in a way that it can be turned by hand. Assuming, what I propose with the 2 BB tools works, in theory I would be able to tighten the 2 cups firmly and since the cups
are pressing against the frame, will I have any issues with this loose BB shell?

2. Can the BB shell be glued?

Many thanks
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Old 03-28-21, 03:19 PM
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rubiksoval
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There are some specific loctite compounds that may help (similar issue with Trek BB90 in which the carbon gets ground out a bit and bearings move).

Might just be time for a new frame. I've never heard of an entire bb shell coming out, but I guess stranger things have happened.
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Old 03-28-21, 03:51 PM
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Suggest OP ask to have this moved to bike mechanics threads.
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Old 03-28-21, 08:28 PM
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Old 03-28-21, 09:16 PM
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I have a loose PF30 Al shell in crabon. It allows the cranks arms to move quite a bit. I checked out Calfee and didn't directly ask them but they state up front they don't do alloy to carbon bonding. I tried to work some epoxy into the crack but it didn't do much. At first it was just on the drive side but now the NDS is also loose.

scott s.
.
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Old 03-28-21, 10:30 PM
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Originally Posted by scott967 View Post
I have a loose PF30 Al shell in crabon. It allows the cranks arms to move quite a bit. I checked out Calfee and didn't directly ask them but they state up front they don't do alloy to carbon bonding. I tried to work some epoxy into the crack but it didn't do much. At first it was just on the drive side but now the NDS is also loose.

scott s.
.
I wonder if the Praxis type of BB would work? PRAXIS COLLET | Praxis Works (praxiscycles.com). Wheels MFG and a couple of other companies have similar screw together BBs for PF30 also, which might work.
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Old 03-29-21, 12:33 AM
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Originally Posted by scott967 View Post
I have a loose PF30 Al shell in crabon. It allows the cranks arms to move quite a bit. I checked out Calfee and didn't directly ask them but they state up front they don't do alloy to carbon bonding. I tried to work some epoxy into the crack but it didn't do much. At first it was just on the drive side but now the NDS is also loose.

scott s.
.
Mine is threaded which makes me a bit optimistic that the cups, if tighten up a bit, press against the frame and may help even if the shell is loose. In my case there is no play in the crank arms
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Old 03-29-21, 01:15 AM
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Where's the naming and shaming of the companies who made these two frames?
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Old 03-30-21, 05:36 AM
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tombell
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Originally Posted by Kimmo View Post
Where's the naming and shaming of the companies who made these two frames?
My intention is not to put shame on the manufacturer since, although rare, this can happen. I have contacted them, since opening this thread and they replied that this can be repaired by a shop that specializes in carbon repairs.
Unfortunately there is no warranty since the bike is some years old. In any case, I am waiting for a 2nd BB tool I ordered, in order to try my theory
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Old 04-08-21, 11:59 PM
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Hi all
UPDATE regarding the issue I posted, that may help others in the future.
The problem was due to an adaptor installed like this one.
/www.amazon.com/FSA-BB30-to-BSA-Adapter/dp/B004N99NG6
This adapter was turning actually, since it was not glued and not the original insert from the factory.
I got the bike second hand, so this was probably done from the previous owner.
Anyway, the bike shop sorted it out.
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Old 04-09-21, 09:53 PM
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Originally Posted by tombell View Post
Hi all
UPDATE regarding the issue I posted, that may help others in the future.
The problem was due to an adaptor installed like this one.
/www.amazon.com/FSA-BB30-to-BSA-Adapter/dp/B004N99NG6
This adapter was turning actually, since it was not glued and not the original insert from the factory.
I got the bike second hand, so this was probably done from the previous owner.
Anyway, the bike shop sorted it out.
what was the solution? I imagine it was just to use 2 BB wrenches?
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Old 04-10-21, 12:16 AM
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The adapter was removed and a new pressfit BB was installed that fits the original shell
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Old 04-10-21, 10:26 AM
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Originally Posted by tombell View Post
The adapter was removed and a new pressfit BB was installed that fits the original shell
That works too
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