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  1. #1
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    Gain Ratio: Single speed fatbike and Kanrd + Rabbit Hole

    I ride single speed exclusively. For gravel, for endurance races, for trail.
    Last year I logged around 8,000 miles on my single speed fat bike (floyds and hudus). When the 29 x 3.0 tires arrived (knards) I mated 2 pair of them with a rabbit hole rims.

    The difference between wheel diameter is significant. And, gear inches and gear ratios don't tell the whole story in capturing the effort required, a 26" fatbike vs 29+.

    But the more obscure "gain ratio" does. If Sheldon Brown were alive I'd give him a call and geek out.

    30.66 = 29x3.0 tire (Knard tire)

    Gear inches:
    34 x 15 ring/cog = 2.26 : 69.29
    Gain ratio:
    389mm/175mm = 2.225
    2.225 x 34/15 = 5.04

    30 x 14 ring/cog = 2.142: 65.69
    Gain ratio
    389mm/175mm = 2.225
    2.148 x 30/14 =4.77


    Fatbike
    29.15 = 26x45Nrth and 29er Racing Ralph, 29 x 2.35 (there's a .02 difference actually).
    34 x 15 ring/cog = 2.26 : 66.3 gear inches
    Gain ratio
    370mm/175 = 2.114
    2.114 x 34/15 = 4.70

    The gain ratio does help.

  2. #2
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    I don't see where gain ratio does anything beyond gear inches except account for crank length. You seem to be using the same crank length in all cases so why did gear inches fail you?

  3. #3
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    Gear inches don't so much fail, as much as crank arm length, when factored, account for percent of leverage and thus provide detail. The percent of leverage for a 175mm crank with a 29 x 2.0 tire is different than a 175mm crank with a 29 x 3.0 tire.

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