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Bottom Bracket installation

BigChainzBigChainz Posts: 2
edited September 2018 in Workshop
Hey guys 8) , I have a alpine competition road bike that used a Shimano BB-6400( 68×113, 1.37×24.)
I go to replace it with a shimano BB-un55 (same dimensions), but one side of my bike's BB shell is smaller than the other. Any clues on how to install the new BB?

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  • BigChainz wrote:
    Hey guys 8) , I have a alpine competition road bike that used a Shimano BB-6400( 68×113, 1.37×24.)
    I go to replace it with a shimano BB-un55 (same dimensions), but one side of my bike's BB shell is smaller than the other. Any clues on how to install the new BB?
    The 6400 is a symmetrical square taper BB for Ultegra. It should just unscrew with the standard square taper extractor. Be careful though, the drive side unscrews clockwise ( if it’s English threaded). The new square taper UN55 just screws in to the existing threads, the fixed ( drive side ) first, then the non drive side ( plastic ) collar screws on.
  • BigChainz wrote:
    Hey guys 8) , I have a alpine competition road bike that used a Shimano BB-6400( 68×113, 1.37×24.)
    I go to replace it with a shimano BB-un55 (same dimensions), but one side of my bike's BB shell is smaller than the other. Any clues on how to install the new BB?
    The 6400 is a symmetrical square taper BB for Ultegra. It should just unscrew with the standard square taper extractor. Be careful though, the drive side unscrews clockwise ( if it’s English threaded). The new square taper UN55 just screws in to the existing threads, the fixed ( drive side ) first, then the non drive side ( plastic ) collar screws on.

    Its not what he asked, your habit of spewing whatever passes vaguely as consciousness is unwavering.

    OP please ignore Bottom Briquette
  • imposter2.0imposter2.0 Posts: 10,837
    The 6400 is a symmetrical square taper BB for Ultegra. It should just unscrew with the standard square taper extractor. Be careful though, the drive side unscrews clockwise ( if it’s English threaded). The new square taper UN55 just screws in to the existing threads, the fixed ( drive side ) first, then the non drive side ( plastic ) collar screws on.

    If you had any clue, you would know that the ends of the 6400 are not symmetrical.. :roll:

    The standard UN55 type extractor will not work on an old style 6400. One side needs a c-spanner and a peg spanner, while the other side has two large flats on it. As Vino says, you really should make sure you have the relevant knowledge before you type..

    To the OP - unlikely that your BB shell is not symmetrical - but the 6400 has different sized ends on it which may make it appear that way. Would need to see a pic otherwise..
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