so, was helping a mate change his drivetrain over tonight – go to the BB and the drive side external BB cup was pretty much hanging off – it was being held in by the tension on the non drive side crank pinch bolts.

once we got the BB cups out, the drive side threads are virtually gone and the new BB will not screw in as there is no purchase on the threads.

it's an alloy frame (2007 fuel EX)

is this something that a tapping tool would sort out? or is it altogether more serious?

He's off to Afan on friday so needs it fixed pronto!

Cheers, wise clever people.

Altogether more serious, you can't tap a thread in something that's not there.Best bet is to contact somebody like Argos Racing Cycles in Bristol, they may be able to do a same day ream and sleeve if you can get the bike to them.

hmmm… that seems to be along the lines that I was thinking….

im afraid altogther more serious is the answer

oh dear. so what might have caused this then? I don't think he's had the BB off since he bought the bike. I've never seen it before, so surprised it's happened though.

i guess it was cross threaded on original fitting, overtightening seems unlikley given the torque for BB cups, but you never know

cant see how you could prove it though – most people will assume you wrecked it either by failing to remove the cups or by bodge fitting a new BB.