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  1. #1
    Canadian Chick Aquakitty's Avatar
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    Jun 2009
    BC, Canada
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    Need some newb info on gear ratios

    So I am converting my spouses bike to a single speed. He is pretty new to cycling. Anyways after trashing a few derailleurs I decided I am going to put him on an internal hub (waiting on the 11 speed alfine coming out in sept.) Until then I am putting a single sped freewheel conversion in.
    This is the first time I ever have done this, I of course read all the material on the subject esp. sheldon brown's info, where he suggests a 2:1 ratio.

    So I though I would put him on a 38t front and 16t in back.. not quite 2:1 but close enough.. so I ordered a fire eye 14/16 9speed conversion kit found here.

    Then, today, I put him on my old 12 speed and got him to find the gears he was comfortable going up hills with... we do a lot of offraod trail riding and theres tons of hills in my area.

    Uho oh.. problem... the ratio that is comfortable for hill climbing and general use for him (and I don't blame him for that matter) is more like 1.2! I think it was a 32T in back and a 39T in front.

    Whoops, I ordered a 16T... and the biggest fire eye sprockets go in the back is 18T.. lol so what now I would need a freaking 20T or 22T on the front? Every single speed crankset I look at only goes to 38T most are 44 or 46T.. so I would need a 58 BCD compact mtb crank not really what I was going for.

    Is this a common issue or am I missing something.. I can't see using such a big ratio for hilly areas or offroad riding it'd be ridiculous.. what am I missing?

    Thanks in advance

  2. #2
    Join Date
    Apr 2010
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    You've misread, you need a gear ratio of ~3:1.
    If you've ordered the 16t sprocket, get a 42t chainring. It gives a ratio of 2.6 which is high enough to go reasonable fast on flat, but might take a bit of work to climb.
    Last edited by Squirrelli; 05-05-10 at 10:02 PM.

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