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  1. #1
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    Drivetrain Question

    hello,

    ive bought a niner EMD Frame, i have transfered most of the parts from my 26", aside from wheels and forks,

    i have a question im sure has been answered but cant see it in the forum.

    " do 29 er wheels need a different sized cog system at front and rear to turn the bigger wheels, ?

    ive looked at what the manufacturers are turning out some have same sized cogs on 26 and 29, this cant be right , any experiences, ideas , arguments ?

    i race xc and the 29 is faster overall but slow on starts, i would appreciate any insight,

    thanks

  2. #2
    1*14*29*2.1 & 1*1*29*2.4
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    same gears, bigger legs

  3. #3
    R.I.P. DogFriend
    Reputation: jeffj's Avatar
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    What drivetrain combo are you running (chainring and cassette sizes)?

    If you want, I'll run the gear inch numders and post them up, or you can do a search for an online gear inch calculator. I use 88.6" for the 29er circumference and 88.3 for 26" wheels (because that's what the rollout was on wheels I had).

  4. #4
    beater
    Reputation: evasive's Avatar
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    No. Most people who claim they need smaller gearing are looking at the low end of their drivetrain, and if you're racing XC that's probably not your priority anyway. Give your existing drivetrain a try and see if it works for you. You can always spend the money to change down the road.
    "Back off, man. I'm a scientist." - Dr. Peter Venkman

    Riding in Helena? Everything you need to know, right here.

  5. #5
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    Well, there's no such thing as 29er specific drivetrain but you can certainly benefit from a different setup than the one you might be running on your 26.

    For years we have been using 3x cranksets, in my 26 bikes I could get into the 44 big ring on flats and roll all the way, once I built my first 29 bike I went with 44/32/22 and 11/34 cassette, the thing is that I spent almost all the time on the 32 ring, the granny was way too granny and the 44 ring required tons of effort in anything it was not a flat.

    Then I moved to 2x10, 39/26 and 11/36 cassette and I don't miss any gear, the only thing is that you won't be able to hit 50 MPH at least it's a BIG hill
    Niner Jet 9
    Santa Cruz Highball Carbon

  6. #6
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    Short answer: No. There's no 29er-specific requirements for a drive train. As with a 26er, they can be set up any number of ways, ranging from single speed to 3 x 10, with various ring and cassette sizes, plus some 11 speed cassette options. There are more possibilities than ever.

    However, because a 29er wheel has a bigger circumference, one pedal rev moves you a bit further than on a similarly geared 26er. So that pedal rev is actually doing more work, and is a bit harder. The effect is roughly equivalent to losing your granny gear.

    There are 2 common ways to get granny back:

    The easiest way is to get a cassette with 36 tooth big cog. In 9-speed, there only one ready-made option, the Shimano HG-61, which good but a bit on the heavy side. In 10-speed, there are more 36t cog options available.

    The other way is to replace your 22t or 24t inner ring with a 20t ring. ActionTec makes one. Installing it will likely require some filing and fiddling, as this really pushes the boundaries of what will fit on a standard spider.

    Or, do both, and get a great-granny for crawling up steep chunk with rubbery legs.
    Use it, use it, use it while you still have it.

  7. #7
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    Thanks to all

    thanks for your time in replying i have decided to go with the following

    combination; a shimano 22- 36 chainset


    1 Shimano XT M771 10 Speed MTB Cassette - Each - 11-36

    would it be prudent to put a larger big ring at front, remember this is for xc racing,

  8. #8
    turtles make me hot
    Reputation: NYrr496's Avatar
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    My Stumpjumper FSR originally came with the exact same drivetrain as my friend's 26er.
    I swore up and down I needed slightly different gearing.
    I swapped the cranks from 175 to 180, ditched the big ring and swapped the granny from 20 to 24. Now I have 32, 24 up front and I swapped the cassette from 11-34 to 11-36.
    I find the bike infinately more rideable and I use a wider range of the cassette.
    Just my findings.
    I like turtles

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