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  1. #1
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    I just bought an older Trek (lugged steel) from a garage sale, and it needs some major work. It currently has a triple chainring, but two of the chainrings are missing some teeth and the bottom bracket has a nasty wobble. I thought I'd just install a double crankset and buy a new bottom bracket.

    What length BB spindle do I need for a double crankset? This is something I haven't had enough experience with to fully understand -- is this something that's regulated, or is it different from bike to bike? Can I always use x-length with doubles and x-length with triples? Is it something specified by the bike manufacturer, or the crank manufacturer?

    Thanks guys!
    Poop will always be funny.

  2. #2
    Aluminium Crusader :-)
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    It's usually specified by the crank manufacturer. So, once you decide what cranks you want, this will determine the type and width of the bottom bracket.

    Having said that, there's a slight chance the Trek could have not have the standard, English bottom bracket shell.

  3. #3
    Chronic Tai Shan ofofhy's Avatar
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    Sheldon Brown has a darn informative site.

    http://sheldonbrown.com/bbsize.html
    From Craig's List: IF its a singlespeed that means----all the other parts are broken cut off and dumped...dont buy singlespeeds, the bikes will make your balls fall off

    * no -- it's NOT ok to contact this poster with services or other commercial interests

  4. #4
    Senior Member sydney's Avatar
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    Quote Originally Posted by 531Aussie

    Having said that, there's a slight chance the Trek could have not have the standard, English bottom bracket shell.
    There is no chance of that so why muddy the water.

  5. #5
    '07 Dean El Diente
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    Trek uses English bottom brackets?

  6. #6
    Senior Member DannoXYZ's Avatar
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    If he bought the bike in the U.S. most likely it's an English BB...

    Quote Originally Posted by Slacker
    I just bought an older Trek (lugged steel) from a garage sale, and it needs some major work. It currently has a triple chainring, but two of the chainrings are missing some teeth and the bottom bracket has a nasty wobble. I thought I'd just install a double crankset and buy a new bottom bracket.

    What length BB spindle do I need for a double crankset? This is something I haven't had enough experience with to fully understand -- is this something that's regulated, or is it different from bike to bike? Can I always use x-length with doubles and x-length with triples? Is it something specified by the bike manufacturer, or the crank manufacturer?

    Thanks guys!
    Decide on a double-crankset first, then pick out the matching BB. The manual will give you a range of BB spindle-lengths to work with, anywhere from 107-125mm+ lengths. You then match up the crankset to the rear-dropout widths on your particular bike, 126mm for 6/7-speeds up to the current 135mm. Pick the spindle-length that works for your particular bike.

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