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  1. #1
    Ride for Life wearyourtruth's Avatar
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    formula/program for converting speed to RPM and vice versa?

    is there a formula or program that allows me to convert my mph to rpm based on my gear ratio? or vice versa. just curious really but i haven't found anything online.
    before posting, a "noob" should always ask themselves "could this have been answered by first visiting Sheldon Brown

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  2. #2
    * adriano's Avatar
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    diameter(mm)*pi*rpm*60/1609344

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    There's this thing called Google... took me about 7 seconds.

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    Low car diet JiveTurkey's Avatar
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    http://sheldonbrown.com/gears/

    Set to "MPH @ 100 RPM" (or "KPH @ 100 RPM"). Once you know your speed at 100 RPM, it' pretty easy to calculate your RPMs at other speeds.

    E.g.: If 15 MPH = 100 RPM, then new RPM = [X/15 * 100], where "X" is the new speed.
    If your new speed equals 16 (meaning, "X"), then your new RPM = [16/15 * 100] = 106.7 RPM.
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    Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.

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  6. #6
    neato teedoff087's Avatar
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    Yeah ^^^ What he said. Rabbit does exactly what you want. You can also download the applet so you don't have to go to that webpage every time you want to calculate.

    http://software.bareknucklebrigade.com/ (click "Outside Browser")

  7. #7
    Elitist Troglodyte DMF's Avatar
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    Quote Originally Posted by wearyourtruth View Post
    is there a formula or program that allows me to convert my mph to rpm based on my gear ratio? or vice versa. just curious really but i haven't found anything online.
    RPM of the wheel? Or RPM of your feet (cadence)?

    If RPM of the wheel, then gear ratio is completely irrelevant. See adriano's formula (which appears to be correct).

    If RPM of your feet, it's only slightly more complicated. You'll need to use gear ratio to determine wheel RPM.
    Stupidity got us into this mess - why can't it get us out?

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