Sheldon Brown's gear calculator- Mtbr.com
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  1. #1
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    Sheldon Brown's gear calculator

    Hi,

    I'm interested in working out equivalent gear ratios, i.e. when does 32x16 require the same amount of effort as 36x18?

    The reason is I've got a Surly 1x1 using 32x16 and have a 38 tooth chainwheel which I fancy trying on my cross check with 28(9)" wheels

    I've been playing with the calculator and have a the following numbers

    For 26"
    32 - 34 - 36
    14 - 4.3 - 4.6 - 4.9
    16 - 3.8 - 4.0 - 4.2
    18 - 3.4 - 3.6 - 3.8
    20 - 3.0 - 3.2 - 3.4

    Is it true that 32x16 = 36x18 (3.8) or than 32x18 = 36x20 (3.4)?

    For a 27" wheel (not quite a 700c 29") wheel but I hope you get the idea of what I'm aiming at.

    32 - 34 - 38
    14 - 4.5 - 4.8 - 5.3
    16 - 3.9 - 4.2 - 4.7
    18 - 3.5 - 3.7 - 4.1
    20 - 3.1 - 3.3 - 3.7

    Is [email protected]" (3.8) feel about the same as [email protected]" (3.9)
    if you ignore tyre choice, surface area etc.

    I understand that 29" bikes require a 10% higher gear than 26" due to a 10% bigger wheel. I'm just looking to make comparisons via Sheldon's calculator. It's a very nifty thing BTW.

    Rob

  2. #2
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    Quote Originally Posted by English Bob
    Hi,
    I'm interested in working out equivalent gear ratios, i.e. when does 32x16 require the same amount of effort as 36x18?
    Rob
    Always the same effort (on the same bike).

    If you're trying to convert to a 29" bike then you've come close enough in your calculations. What you "feel" is going to override the accuracy of the calculations, unless you account for the greater rotating mass of the larger wheels, which means slower accelaration for the same effort.

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