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  1. #1
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    Any disadvantages of low Q factor?

    I have sram force cranks on both my road and cross bikes which measure out to 145.5mm Q-factor.

    I have been planning to upgrade my cranks on my MTB to XX1s. But I have been on the fence between the low and high Q-Factor options. The low Q-factor GXP option measures out to 156mm, while the high Q-factor measures out to 168mm.

    The 168mm is close to what I have been riding on my MTBs for the past few years, but the 156mm is going to be much more similar to my road and cross bikes.

    I do about 50% of my training on the road, and 50% on the MTB.

    So to the heart of my question, are there any disadvantages for low Q factor?
    Obviously, you need a q factor that biomehanically fits your body. But if we are comfortable riding on the road with low Q, I dont see any issues with it on the MTB...

    Do you lose any bike handling or stability? I know DH bikes have wide Q factors. But I am no expert in that field. It may simply be an byproduct of wider hubs and chainline.

    Another thought is that a narrow Q factor will put your weight closer the center line of the bike when the outside pedal is loaded in a corner.

    Anyway, look forward to hearing what yall think.
    Sheepo
    Raised in a Chicken-Coop by Chickens

  2. #2
    AZ
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    The wider Q on mtb's is derived from build constraints, fitting a wider tire requires things to be spread out.

  3. #3
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    Sometimes the narrow Q cranks can have clearance issues. The crankarms can be too close to the frame and (more commonly) a rider's heels can contact the chainstays. I have size 44 feet and set my cleats up in a somewhat "toes out" position. My heels hit the chainstays on my Niner Jet9 RDO with narrow Q XX cranks. I have to add pedal washers and push my cleats all the way to the inside of my shoes for clearance. Not ideal. Something to think about when trying to decide between two cranks. As for handling differences? I really can't see Q factor making a noticeable difference.

  4. #4
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    I'm very duck footed. Standing normally, my feet are perpendicular to one another. I usually try to get as wide of a Q-factor as possible (cleats mounted as far inboard as possible, pedal shims, etc.) so that my ankles aren't twisted in a way that's not natural for them.

  5. #5
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    I switched from XT cranks to the narrower XX1 and like the q-factor much better. I have size 45 shoes and zero issues. But like others have said you might have issues.

  6. #6
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    Awesome, thanks guys! I figured my cranks arms would clear, but I diddnt account for my size 45.5 feet!

    Ill have to do some measuring and see if they clear. If so, it doesnt sound like there are any disadvantages to the narrow Q-Factor.

    Sheepo
    Raised in a Chicken-Coop by Chickens

  7. #7
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    From a bike handling perspective, I don't think Q-factor will make any difference. If you are comfortable with a lower Q-factor, go for it. Switching between road and mtb will be that much more seamless.

    I train about 60-40 (road and mtb) and when switching, I do notice the Q-factor for the first few minutes only, so not a problem for me. Actually, most of my winter training is on the CycleOps 300Pro, which has a Q-Factor similar to my mountain bikes.
    My rides:
    Lynskey Ti Pro29 SL singlespeed
    GF Superfly 29er HT
    S-Works Roubaix SL3 Dura Ace
    Pake French 75 track

  8. #8
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    Quote Originally Posted by PlanB View Post
    Sometimes the narrow Q cranks can have clearance issues. The crankarms can be too close to the frame and (more commonly) a rider's heels can contact the chainstays.
    I had same issue with XO crank on Giant Anthem and with my Ridley cross bike (both double ring cranks).

    No issues with Giant road bike (Campy Crank, which is known for it's narrow Q-factor).

    So it depends on chain stay geometry.
    Head Coach, Ben Lomond HS MTB Team
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