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Thread: Crank/BB combos

  1. #1
    I Have Gnarly Potential
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    Crank/BB combos

    Its been a while since ive bought a new crank, most seem to be going to the crank/integrated BB combo, which is cool i guess.

    But what happened to BB width? on BB you get the specific mm width for your bike.

    Ive never seen a new crank/BB combi (like a FSA or Shimano LX/XT/XTR) even refrence the width of the axle,or BB casing, or anything like that.

    How do you know if it will fit? or has all bike frames now also use just 1 standard size? (im looking for it on my Gary Fisher, 4-5 year old bike)

  2. #2
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    The external bb type crank doesn't talk about spindle length as it's fixed, literally, the spindle is attached to the driveside crank; they come with spacers to account for the bb shell width (most of these cranks are intended for 68 or 73 shell widths, altho some of these types of cranksets are offered in wider shell widths as well).
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  3. #3
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    Great thanks

    Thats acually kind of cool, keeps the crankarms at a predetermined fixed length, instead of going closer together/wider apart depending on the frames BB cup width.

  4. #4
    JmZ
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    Quote Originally Posted by Krause
    Great thanks

    Thats acually kind of cool, keeps the crankarms at a predetermined fixed length, instead of going closer together/wider apart depending on the frames BB cup width.

    Uhhh....I think that's actually a drawback to this style of cranks.

    It's a fixed width. Means if I'm going to do a 1X or a 2X ring setup, I'm hosed. Also if I want to adjust my chainline, I have to use spacers instead of a part that fits right to begin with, and this could be a pain if you've got a suspension pivot near that BB junction.. Also, Also means my pedals will keep getting further apart. I'll have to change pedals to get a different width between 'em.

    Honestly the Phil Wood BB and a set of Middleburn cranks are looking really good right now.

    And yes, I'm a retrogrouch.

    JmZ
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  5. #5
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    Quote Originally Posted by Krause
    Great thanks

    Thats acually kind of cool, keeps the crankarms at a predetermined fixed length, instead of going closer together/wider apart depending on the frames BB cup width.
    That's not a good way to think about crank arms. Not all external type bb cranksets will have the crankarms with the same exact width (or "q" factor, as it has been called). Just like not all previous designs did, either. Don't confuse the "q" factor with shell width or spindle length, they're not necessarily related. What the external types do is fix your chainline a bit wider than other designs did, and gives you less flexibility for chainline as JmZ points out.
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