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47mm/57mm brakes

potspots Posts: 109
edited December 2009 in Workshop
hi just a quick question.
i am thinking of building a winter training bike that requires 47mm/57mm brakes to clear the mudgaurds.
will brakes that are specified 49mm fit ?


  • whyamiherewhyamihere Posts: 7,509
    Only if you're very lucky.

    Edit: And 49mm brakes tend to be a bit of a git with full mudguards.
  • andrew_sandrew_s Posts: 2,511
    No. You will need to get 47-57mm brakes.

    A frame will require a specific brake drop that depends only on the frame dimensions (and the size of wheel in use). Since standard brakes are 49mm max drop, there's no point building a frame with a 48mm brake drop and then specifying that you need a 47-57 brake even though it would work.
    The frame will almost certainly have a drop at the large end of the 47-57 range. How close depends on the tolerances the frame builder was working to.
  • jrabjrab Posts: 99
    I already had a set of 49mm calipers and the brake blocks were only 1-2mm short of the right position. Rather than forking out on new calipers I got a round file (same width as the caliper slot) and extended the slot a bit. Plenty of material at the end of the arms so no real risk to integrity of caliper.

    Took a while though, although you could use a Dremel if you're careful.

    Obviously won't work if you need a much longer slot, but worth a look if you already have standard calipers.

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