Can I use a diff size BB?- Mtbr.com
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  1. #1
    Not a Barry supporter.
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    Can I use a diff size BB?

    I have a Sugar and run RF LP cranks. I don't hae a whole lot of clearance b/w the frame and crank. The BB is 73x113. Would there be a big problem if I went 73x118? All I should have to do is adjust the deraillers...correct? Or would the threads be poking out of one or both sides?

    Thx for the help!
    Why would I need more than one gear?
    @A_SingleSpeeder
    EPA = crooks!

  2. #2
    Perpetually single track
    Reputation: ibmkidIII's Avatar
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    118 is just the spindle (axel) length I believe. No threads sticking out,. but good chance it'll screw up your chain line though. I think that'd cause extra wear on the drivetrain and make for shitty shifiting.
    The more out of shape you are, the steeper the hill looks.

  3. #3
    Derailleurless
    Reputation: Speedub.Nate's Avatar
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    Range of adjustment...

    Quote Originally Posted by Crash_FLMB
    I have a Sugar and run RF LP cranks. I don't hae a whole lot of clearance b/w the frame and crank. The BB is 73x113. Would there be a big problem if I went 73x118? All I should have to do is adjust the deraillers...correct? Or would the threads be poking out of one or both sides?
    Front derailleurs have a very narrow operating range, generally between 47 and 50 mm as measured from the center of the frame to the center of the middle ring.

    The 113 splined spindles will generally get you around 47 to 48mm, and 118 splined spindles will generally put you in the 50mm range.

    "Ideal alignment", i.e. the middle ring aligned with the center of the cassette, is around the 47 ot 48mm mark.

    You can get away with shifting your chainline to the outside a bit without too much trouble. In fact, I prefer 50mm chainlines on Fisher bikes due to (1) the wide 73mm bottom bracket shells (most other brands go with 68mm), (2) the short Fisher Genesis chainstays, and (3) the fat seat tubes (are they still using 34.9mm diameters?). But if you're using a 113 now and aren't having any shifting issues, why change?

    Like IBM Man mentioned, you won't see any extra threads by going to the longer length -- that's a function of shell width.

  4. #4
    Crank monkey
    Reputation: Smytty's Avatar
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    I'd stay with the 113.

    I put a 126mm ES-51 BB (approx equivalent to a 118mm square taper) on my Sugar + and the shifting went for sh!t, even when riding on pavement. I switched to a 121mm (equivalent to 113mm) and everything went back to normal. If you go wider than 113, you might open yourself up to a lot more chainsuck. That's a theory of mine, nothing more.
    Cheers,
    Smytty

  5. #5
    Not a Barry supporter.
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    Thanks fellas. I think this seals it and I'm gonna stick with the 113mm.
    Why would I need more than one gear?
    @A_SingleSpeeder
    EPA = crooks!

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