My carbon CX frame has a one piece alloy BB shell which has come unbonded from the frame.

It’s not loose enough to pull out, in fact you can only get it to turn when you apply a good deal of force to a BB cup.

Any ideas how I might fix it back into the frame?

Ta Rich

inject loads of glue through the bottle cage holes 😉

I’m guessing it’s bonded in with epoxy – could you heat it up to get the epoxy to debond (which it already has!) and then hope it rebonds as it cools?

Alternatively you could heat it to get it out and then rebond it back in with new glue.

woulnd’t heating the alloy make it expand?

pack the shell with dry ice and it’ll fall out 🙂

Heating a carbon fibre frame is sure to be a good idea?

heating a carbon frame is a BAD IDEA, but regluing is the best idea

How about drilling a small hole underneath the BB (roughly where the cable guide already be) and using a small self-tapping screw into the BB shell from there. That would stop it rotating.

I’m guessing it’s bonded in with epoxy – could you heat it up to get the epoxy to debond (which it already has!) and then hope it rebonds as it cools?

Thermosets don’t work like that. Once they are cured that is it.

I don’t know what the people who fix these would do but I would consider vacuum bagging the BB area and infusing it with some epoxy to try and get it to bond in.

Heating is not a problem, they are cured using heat and you can take it back up to near it’s cure temp with no worries. But you need to know the cure temp so you don’t overdo it and have a well controlled oven that is big enough.

OK ta some good ideas. I’m going to stick a new BB in there and see if it plays nice before I do anything radical.