Gear ratio confusion...

Gobs
Gobs Posts: 296
edited January 2017 in MTB workshop & tech
Current bike (for my partner) is a 2011 Boardman HT Comp with the 3x9 setup (22/32/42). She has some killer hills at home so is often in the granny ring for climbs. She's thinking of adding an FS to the garage and the Boardman FS Pro is top of the list with its 1x11 setup. 22 teeth front, 42 rear (for the lowest). I don't know the number of teeth on the HT Comp's rear cassette, but is the new 42 tooth rear cog likely to be the same as her current lowest gear?

Comments

  • The Rookie
    The Rookie Posts: 27,812
    No....

    Divide one by the other (rear by front) to get the number of crank turns per turn of the wheel, the bigger number the better.

    The 3x9 will be 22:34 so just over 1.5:1 in first gear, the pro isn't a 22 front I think it's a 32 so 32:42 is just under 1.33:1.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • robertpb
    robertpb Posts: 1,866
    The Boardman FS will also have bigger wheels, giving a higher bottom gear, on the FS you'd need to have a 28t chainring to get close.
    Now where's that "Get Out of Crash Free Card"
  • Gobs
    Gobs Posts: 296
    Thanks, very helpful. So in essence she'll have to man up considerably to get it uphill :lol:
  • The Rookie
    The Rookie Posts: 27,812
    Gobs wrote:
    she'll have to man up
    Erm, yes I guess....

    It depends on which gears she uses in the granny ring really! 22/34 I could never use, you're going so slow its hard to stay upright, 22/30ish was about my limit.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Rightarmbad
    Rightarmbad Posts: 216
    Go to this and work it out for yourself.
    http://gear-calculator.com/

    It's a great utility to play with gear ratios.
    You can change tyre/wheel size, amount of front cogs, amount of rear cogs and it will even tell you your chainline angle.
  • LimitedGarry
    LimitedGarry Posts: 400
    http://gears.mtbcrosscountry.com#26I300I208X27.5I13I3
    Check out those ratios. Can't know what cassette she has on the old Boardman, but the comparison is actually pretty good. Even if she has an 11-36 cassette, I don't think she'll struggle in climbs.

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