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  1. #1
    West Virginia Cyclist
    Reputation: lalahsghost's Avatar
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    Problems with narrowing Q-factor

    So, I've taken off the cruddy stock crank that came on my '09 GF Cobia, and replaced with with a Sugino square taper triple - converted into a 32/20 double.

    My goal is to get the cranks as close as possible to the chainstays for knee problems.

    Well, when I bought the Sugino crank, I had to separately purchase the non-driveside crank arm.

    Now with a 110mm square taper spindle, driveside is PERFECT, but NDS is whacking it a bit....

    Is there a chance I could find another NDS crankarm that is splayed out a bit to not hit the chainstay (Are GF chainstays asymmetric?) before going to a 113mm bottom bracket?

  2. #2
    mtbr member
    Reputation: J.B. Weld's Avatar
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    Your frame will only allow you to go so low. You could fool around trying to find another crank arm that clears but I doubt you'll do better than the 3 extra mm of the next size BB (113).

    There are pedals that can lower your Q a few mm, but your pedaling style or foot position may not allow them.

  3. #3
    West Virginia Cyclist
    Reputation: lalahsghost's Avatar
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    Quote Originally Posted by J.B. Weld View Post
    Your frame will only allow you to go so low. You could fool around trying to find another crank arm that clears but I doubt you'll do better than the 3 extra mm of the next size BB (113).

    There are pedals that can lower your Q a few mm, but your pedaling style or foot position may not allow them.
    Thanks for the quick reply J.B.! This is what I was expecting, but not what I was hoping. 113mm square taper bottom brackets aren' t too expensive, so I don't really feel like I'm losing out.

    Thanks again.

  4. #4
    Fat-tired Roadie
    Reputation: AndrwSwitch's Avatar
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    If there's only a little bit of interference, with some bottom brackets you can adjust the centering with spacers. Not all, and sometimes it would only be possible in one direction. But something to look at for fine-tuning.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  5. #5
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    Yes, something like a Phil Wood BB lets you adjust the cranks in and out about 2.5mm each direction and you can also get offset spindles as well. I used one of these on my touring bike to narrow down the Q factor. It had a 122mm BB on it and I got it down to a 116mm with a triple crank. I had to dimple in the chain stay a bit on the crank side to make room for the inner chain ring.

  6. #6
    West Virginia Cyclist
    Reputation: lalahsghost's Avatar
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    Well, thread is done, a 110mm square taper @ 73mm BB width did the trick. This is the first time using a "MTB" square taper bottom bracket, so little did I know the one off my older road bike wasn't ideal (68mm, durrr).

    Everything is peachy keen now.

    Also, at the suggestion of J.B. Weld, I installed my PD-A520's in replacement of the PD-M520's Saved about 2-3mm with that too!

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