Remove/replace alu BB insert in carbon frame?

[peligro]

Hi all, I have an older Fuji carbon frame which I like but for the obsolete bb86 bottom bracket shell.

As the photo shows, the 86.5mm bb shell extends way beyond the frame and has some non structural carbon around the ends.

I would like to have the shell removed and the frame converted to a modern standard. Wondering in particular whether the shell can be debonded (with heat?) without damaging the frame.

Grateful for any advice.

[ms6073]

Short answer, get a new frame as there is no practical means of removing that alloy insert. On a tangent, BB86/PF86 is hardly obsolete and from a technical standpoint, that 'older' alloy shell prevents many of the alignment issues present with curernt generation BB86 frames with an all-carbon bottom bracket shell. Finally, the newer standards like BBRight, BB386, T47, and even Colnago's Threadfit 82.5 all introduce there own set of issues, especially availability of replacement BB's for the more niche standards.

[Nickldn]

It's a legit question: why would anyone really think BB86 is obsolete in 2021?

Wildly popular and well supported more like?

[ms6073]

Ditto. Recently replaced a Soctt Solace disc frameset with a Colnago C64 disc frameset which has a threadfit 82.5 (T45) threaded bottom bracket. I opted to use the BBInfinite PF86 bottom bracket that had been installed in my Scott Solace as the only 'out of the box' theaded solution of which I am aware is the T45 bottom bracket Ceramic Speed made in collaboration with Colnago and which costs nearly US $350.

[Cycomanic]

Short answer, get a new frame as there is no practical means of removing that alloy insert. On a tangent, BB86/PF86 is hardly obsolete and from a technical standpoint, that 'older' alloy shell prevents many of the alignment issues present with curernt generation BB86 frames with an all-carbon bottom bracket shell. Finally, the newer standards like BBRight, BB386, T47, and even Colnago's Threadfit 82.5 all introduce there own set of issues, especially availability of replacement BB's for the more niche standards.

I would not lump BB386 with the others. It really is the only sensible standard of those (except for maybe BB86, whose main issue is that it's specifically made as an anti-SRAM standard).

[peligro]

Regret having opened a can of worms by referring to bb86 as obsolete. Suffice it to say I have a BB30 I really want to use with this frame.

I thought the glue used to fasten metal inserts has a lower melt point than the resin in the carbon fiber itself, and thus the inserts can be removed with heat. Perhaps I am wrong about that.

The metal shell is 86.5mm but the bike was designed form a 68mm shell so the alu tube sticks out either end. Now I am thinking a machine shop could potentially cut off the ends and bore in bearing seats (id is 41, enlarge to 42mm).

[peligro]

Regret having opened a can of worms by referring to bb86 as obsolete. Suffice it to say I have a BB30 crankset I really want to use with this frame.

I thought the glue used to fasten metal inserts has a lower melt point than the resin in the carbon fiber itself, and thus the inserts can be removed with heat. Perhaps I am wrong about that.

The metal shell is 86.5mm but the bike was designed form a 68mm shell so the alu tube sticks out either end. Now I am thinking a machine shop could potentially cut off the ends and bore in bearing seats (id is 41, enlarge to 42mm).

[peligro]

Regret having opened a can of worms by referring to bb86 as obsolete. Suffice it to say I have a BB30 crankset I really want to use with this frame.

I thought the glue used to fasten metal inserts has a lower melt point than the resin in the carbon fiber itself, and thus the inserts can be removed with heat. Perhaps I am wrong about that.

The metal shell is 86.5mm but the bike was designed form a 68mm shell so the alu tube sticks out either end. Now I am thinking a machine shop could potentially cut off the ends and bore in bearing seats (id is 41, enlarge to 42mm).

[peligro]

ack sorry for duplicate posts, can't figure out how to delete them.

[joeyb1000]

I think the heating idea is not possible. The BB would probably be cut out. Someone like Ruckus could do it, but this is not a DIY thing. You will have to decide if it is worth it.

[MayhemSWE]

If there was even a remote possibility of this project ending well for you, you would not be asking for this type of advice here...

[wheelsONfire]

Hi all, I have an older Fuji carbon frame which I like but for the obsolete bb86 bottom bracket shell.

As the photo shows, the 86.5mm bb shell extends way beyond the frame and has some non structural carbon around the ends.

image_2021-04-20_072448.png

I would like to have the shell removed and the frame converted to a modern standard. Wondering in particular whether the shell can be debonded (with heat?) without damaging the frame.

Grateful for any advice.

You probably could send it to a company doing carbon repair work. But then again, is it worth the cost?
It's probably cheaper to buy a used but fitting crankset.

[ms6073]

Suffice it to say I have a BB30 I really want to use with this frame.

Would have avoided a lot of ambiguity had you mentioned wanting to use BB30 from the start. As someone who at one point was trying to find a means of using a BB30 SRM on a BB86 frameset, I am again going to suggest that you will be better served sourcing a BB30 frame. If you want the stiffness of BB30, then a simple solution would be to use a BB386 crank with a bottom bracket applicable to BB86.

[stevesbike]

There's virtually no chance a carbon repair company would even attempt this. I once had a frame with a damaged lower headset bearing cup (carbon molded into frame) and Calfee was the only company willing to try. It didn't end well. What you're asking is many times more complex, including changing the diameter. Even if it worked it would end up being much more expensive than the frame's value and many times more expensive than a compatible crank. I use a 386 crank (power meter) among a BB30, BB86, and a BBright frame - pretty simple to find the right bottom bracket/adapters.