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Thread: What is Q factor?

  1. #1
    MoJo Neophyte Kindacreeky's Avatar
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    What is Q factor?

    Want to replace my BB and Cranks on a 2004 SC Blur. What is Q factor? How can i measure this?

  2. #2
    MoJo Bishop fore's Avatar
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    your q factor is the distance between the outside of each of your crank arms. seeing as the arms are usually opposite each other, measuring can be a little iffy, but one way is to measure from the outside of each crank arm to the seat tube, then add those measurements to the width of the seat tube, and that should give you a decent approximation.

  3. #3
    MoJo Neophyte Kindacreeky's Avatar
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    Thanks. Now, which of the new outside bearing type of BB and cranks will give me the narrowest Q-factor? I am now running an '04 Shimano LX with the Octolink Hollowtech (I) BB and crankset. It is a 68 x 113 BB. I have heard that the new outboard bearing cranksets will widen the Q-factor some.

  4. #4
    MoJo Bishop fore's Avatar
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    i have no idea what crank will give you the narrowst q. a quick perusal of race face and truvativ's websites tells me that q-factor isn't something a lot of manufacturers list on their spec sheets.

  5. #5
    MoJo Bishop fore's Avatar
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    it seems FSA does, actually, and all of theirs seem to be either 169mm or 170mm.

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    MoJo Neophyte Kindacreeky's Avatar
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    Thanks, I will measure the Q factor on my rig tonight. Will get back to you.

  7. #7
    eat, sleep,ride ohiobiker's Avatar
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    Q Factor Measurement

    I suppose that you could remove the left crank, pedal and all, flip it 180 degrees and reinstall it. The crank arms will be right next to each other. Then take the measurement. Hope this helps.

  8. #8
    The William Sapphire of Bike Mechanics
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    car!os's Avatar
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    Kindacreeky....you shouldn't really need to search down the narrowest Q factor....

    the q factor should be taken into consideration if your stance is a bit on the wide or narrow side.....this takes a bit of figuring....hip width, foot width, stance width...

    if you want to find the ideal q factor...have a fitting done...it's part of the fitting....

    there are WAAAAAAAAAAAAAY too many people buying bikes these days and while it's nice to pick out your own parts and build a "custom" bike....leaving out the fitting only means it's a half assed job...to say the least.....

    when you think about it....the fitting should be the FIRST thing people consider when buying a new bike....

    anyway, get fitted and you'll find out the right Q factor for you...then you can use that info to determine which cranks to purchase. if the current crank has a slightly narrow Q factor...they pedals can be spaced further out (to some degree) and vice versa (but than depends ont he crank type).....
    It’s impossible to rate welding/brazing quality by looking at a finished frame joint, even an unpainted one. Files, sandblasting, and a good paint job can take care of that. Such a joint will look stellar unpainted, but won’t last. Yet people all the time look at frames and say, “Nice welding/brazing…” The point isn’t to make you paranoid, just to stop saying things like, “That’s nice welding/brazing,” when you see a painted/unpainted frame. -- Grant Petersen

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