Loose BB = New Frame?

psychle
psychle Posts: 83
edited April 2009 in Workshop
The BB has come loose on my commuter/winter hack. Not the axle, but the entire BB cartridge is loose in the BB shell of the frame.

It's a common square taper Shimano sealed BB cartridge in a 12 year old steel frame (531c).

I took out the BB cartridge and cleaned up the BB shell with degreaser and a wire brush.
When I refit the BB cartridge it screws in forever, ie it never tightens!
The same thing happens with another BB cartridge so it seems likely that the threads in the BB shell are damaged/worn.
Logic would suggest that if the current fit is loose then cutting new threads in the BB shell would remove more material thus creating a bigger opening and an even looser fit.

Does anyone know of a potential fix or does it mean the frame has to be replaced?

"Like a pig towing a cart-load of sausages - I draw my own conclusions"

Comments

  • nicklouse
    nicklouse Posts: 50,673
    you can get threadless BB´s have a chat with you LBS.



    Or if you want to spend then you can get the frame fixed. either machining the whole bb shell out and fitting an insert or cutting and shutting the bb and then re cutting the threads.

    threadless bb is cheaper by a long way.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • redvee
    redvee Posts: 11,922
    Frame buliders charge around £60 for a ream and sleeve of the BB which will give you the option of upgrading the BB in future to HTII or similar as I doubt you can get one of those in threadless form.
    I've added a signature to prove it is still possible.
  • John C.
    John C. Posts: 2,113
    I chucked a frame out for the same reason, Then as I cried :cry: to my LBS in Northallerton they said they had threadless BBs. I cried even more :oops:
    http://www.ripon-loiterers.org.uk/

    Fail to prepare, prepare to fail
    Hills are just a matter of pace
  • k-dog
    k-dog Posts: 1,652
    The easiest way to fix it is threadlock and try and make it stick.

    If that doesn't work then you can have it rethreaded as an Italian thread - they're slightly bigger so that's not too hard.

    Then there's the threadless style already mentioned.

    Lastly you could have someone replace the shell - but that is expensive and you'll need a respray.
    I'm left handed, if that matters.
  • psychle
    psychle Posts: 83
    Thanks for the responses. I'm much encouraged now, I was expecting to have to ditch the frame.

    Didn't know there were threadless BBs but now it looks like this could be just what I need
    http://www.edinburghbicycle.com/ebwPNLq ... 151c003226

    Simple, quick and inexpensive. Ideal for the hack commuter.

    "Like a pig towing a cart-load of sausages - I draw my own conclusions"

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