ratios, gear inches, wheel diameter- Mtbr.com
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  1. #1
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    ratios, gear inches, wheel diameter

    Back in the old days when if it was a mountain bike, it had 26" wheels, so describing gearing in terms of ratios made sense. Nowadays, with larger wheels, speaking in terms of ratios doesn't make sense, but I still see a lot of people talking about 2:1, 34x17, etc.

    Seems like we should be comparing gear inches not ratios. 2:1 on 29" wheels is a lot higher gear (more gear inches) than 2:1 on 26" wheels.

  2. #2
    aka "SirLurkAlot"
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    Quote Originally Posted by OldSkoolMark View Post
    Back in the old days when if it was a mountain bike, it had 26" wheels, so describing gearing in terms of ratios made sense. Nowadays, with larger wheels, speaking in terms of ratios doesn't make sense, but I still see a lot of people talking about 2:1, 34x17, etc.

    Seems like we should be comparing gear inches not ratios. 2:1 on 29" wheels is a lot higher gear (more gear inches) than 2:1 on 26" wheels.
    Gear inches is what I've used for quite some time now, since 2006 when I bought a 29er. It works great and Sheldon's (RIP) gear inch calculator works every time.

    Sent from my SM-G950U using Tapatalk

  3. #3
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    Yup. I hate discussion about gear combos when no one talks about tire size. A 27.5x2.25 and a 29+ tire are the same gear combo are not the same thing.

  4. #4
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    Please, everybody knows the smart kids have long moved past gear inches and gone on to gain ratio.
    http://www.bikingtoplay.blogspot.com/
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  5. #5
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    I am running 48.4 gear inches...
    Salsa Timberjack SS
    -Gears give me headaches

  6. #6
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    Using the application Gear Calculator.

    48.41 here as well, on 3 of my single speeds.

    I can make 11 mph comfortably at 76 rpm.

    Gain is 3.62, but I don't understand that.

    The ratio is 1.67

    Sometimes I want an easier "gear".

  7. #7
    WillWorkForTrail
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    I'm running 32x18 on 29x2.2 tires. Y'all do whatever math with that makes you happy. :beer:

  8. #8
    Downcountry AF
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    Gain ratio takes into account your crank length, which gear inches does not. #cranklengthmatters

    When is someone going to invent a gear calculator that takes into account my oval chainring? I want to know my ratio at each position in my pedal stroke.
    Rigid SS 29er
    SS 29+
    Fat Lefty
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    Stop asking how much it weighs and just go ride it.

  9. #9
    Rod
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    The weight of the wheelset matters too. When are we going to have that discussion? Carbon valors vs a stick redline wheelset

    Sent from my SAMSUNG-SM-G891A using Tapatalk

  10. #10
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    Weight doesn't matter in this context. This is just looking at the mechanical advantage your drivetrain can give you.

    Quote Originally Posted by Rod View Post
    The weight of the wheelset matters too. When are we going to have that discussion? Carbon valors vs a stick redline wheelset

    Sent from my SAMSUNG-SM-G891A using Tapatalk
    http://www.bikingtoplay.blogspot.com/
    RIGID, not "ridged" or "ridgid"
    PEDAL, not "peddle." Unless you're selling stuff

  11. #11
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    Lots of variables indeed. I've always ran 180mm cranks on single speeds on general principle that you need more leverage if you've only got one gear. Will have to look into the gain ratio thing.

  12. #12
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    Quote Originally Posted by Jack Burns View Post
    Using the application Gear Calculator.

    48.41 here as well, on 3 of my single speeds.

    I can make 11 mph comfortably at 76 rpm.

    Gain is 3.62, but I don't understand that.

    The ratio is 1.67

    Sometimes I want an easier "gear".
    Gain ratio of 3.62 means if you rotate the pedals 1 inch, your wheel will travel 3.62; if your pedal travels one foot, your wheel travels 3.62 feet...

    Same with miles, millimeters, kilometers, or any other measurement of distance...
    Salsa Timberjack SS
    -Gears give me headaches

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