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Bottom bracket shell failure(6 posts)

Bottom bracket shell failuretrimble
Jul 7, 2002 6:34 AM
Here's the deal. My carbon bike (8 yr old Basso) has a BB shell that's like a sleeve. The shell is glued into the frame. However after many years and many miles, the adhesive has broken down. The shell and the bottom bracket have shifted to the right 3/8". I can temporarily fix this by wacking it back into place with a rubber mallet. I took the bike to a couple of local bike shops and the answer I got was the same: your frame is toast. They don't recommend trying to reglue the shell back into the frame.

Anyone out there have a similar BB problem - how did you resolve the problem?
re: Bottom bracket shell failureDave Hickey
Jul 7, 2002 6:45 AM
Can you get access to the BB shell? There is an epoxy called JB Weld. If you can remove enough of the shell to get epoxy in, JB Weld is VERY strong stuff. I've reglued a Vitus carbon frame an it's still holding after 2 years. Any good auto parts store will sell it.
cleaning required...C-40
Jul 7, 2002 7:49 AM
Not a bad idea, but to have any chance of holding, the aluminum shell should be removed completely. All mating surfaces should be throughly cleaned with acetone or lacquer thinner, then lightly sanded to promote adhesion. If the parts aren't clean and roughed-up, you won't get a good bond.
I totally agree........... nmDave Hickey
Jul 7, 2002 10:30 AM
WEST Systemsgrzy
Jul 8, 2002 9:26 AM
if you can press out the shell w/out doing any significant damage I'd try to repair it on your own.

West Epoxy makes a kit for etching aluminum in preparation for bonding with epoxy. Just cleamiing it up with acetone isn't sufficient if you want a good bond. You can get the material directly from West Epoxy (aka Guegon Bros.) or from your local West Marine (not the same company). You'll probably wind up with far more material than you'll need, but that's life.
Good adviceNessism
Jul 8, 2002 11:29 AM
Only the order should be to degrease with acetone, sand, and degrease again. It's best not to sand until the grease is removed or some may become imbedded into the aluminum. To attach the shell back in, JB Weld will work just fine. An etching compound isn't reall needed since the parts are getting cleaned with the sanding - just don't wait too long between cleaning and gluing.

The only concern I can think of is the lack of a sealing surface between the carbon and Al. Many of the early bonded carbon frames failed due to corrosion until the mfgers learned to anodize the Al parts before bonding. At any rate, a simple clean up and gluing should last a good long time.