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  1. #1
    stuck in the 90s
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    Jun 2007
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    New question here. shimano un73 weirdness

    hi

    in a fit of "more money than time" i ordered 2 un73 bottom brackets. on one of them there appears to be a washer just past the tapered part of the spindle and it's a little bit stuck, meaning it didn't fall off.

    pictures are worth more than my words so:

    img_2456[1] <---- gets bigger if you click it

    the other one i ordered didn't have this "feature"

    does anyone have any idea what it's doing there?

    thanks

  2. #2
    Former Bike Wrench
    Reputation: mtnbiker72's Avatar
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    Jan 2007
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    15,985
    Some of the later model UN Shimano Square Taper BB's had those to prevent over tightening the driveside crankarm and throwing off the intended chainline (45-47.5 mm at the time). They don't affect the performance of the BB itself...just more funky Shimano weirdness!

  3. #3
    mtbr member
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    Over the years I've seen some Shimano square taper BB's with and some without this washer. Presently I have two UN72's, one with and one without as well as a UN53 and two UN73's, all with the washer. I'd guess it's there for protection of some sort. I wouldn't worry about it either way.

  4. #4
    stuck in the 90s
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    Jun 2007
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    sweet! i can continue in my blissfull ignorance.

    thanks for the help

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