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problem with chainset and old BB

daffyavfcdaffyavfc Posts: 237
edited July 2010 in Workshop
hi

I've got a 12 speed raleigh Mercury from early 90's that had a bent chainset, so much that the inner chainring rubbed and cut into the paint.

I've bought a couple off the net but on each ocassion the inner chainring is in contact with the frame unlike the original one before getting damaged. I've thought about changing the old style cup and cone BB but cannot get anying modern to fit in the hole as it catches on the mouldings inside the BB housing. I'm stuck with a single 42 chainring that works but need a larger one.

would I be able to put spacers or something similar on the BB axle to push the double chainset away from the frame as it just glides on and touches the frame at present???
if not, any ideas???

thanks

Posts

  • Weejie54Weejie54 Posts: 750
    You likely have a BB shell with a Raleigh thread. They used their own 26 tpi threading instead of the standard BSA 24 tpi - on cottered BBs especially. They also had a habit of using a 71mm BB shell which is 3mm wider than a standard British shell (68mm standard, though some BBs are oversize 73mm - like one of my Flying Scots). You could try your new spindle (axle) with the original cups (problem, maybe, if it is a spindle for a 68mm BB) or fit a threadless BB, which can be obtained quite readily. If your BB is 71mm wide you may need a spacer (for a 73mm threadless BB) - or get your shell re-faced down to 68mm (69mm would probably be enough). There are other solutions but, perhaps, I've highlighted the easiest options.

    Threadless BB

    Another
  • bill57bill57 Posts: 454
    What are the mouldings in the BB shell? Are you sure this isn't just part of the plastic cable guide under the BB, which protrudes into the shell?
  • Weejie54Weejie54 Posts: 750
    What are the mouldings in the BB shell? Are you sure this isn't just part of the plastic cable guide under the BB, which protrudes into the shell?
    Good shout - I thought it referred to the thread.
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