26 to 29er gear ratios…

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  • 26 to 29er gear ratios…
  • Premier Icon roverpig
    Subscriber

    It depends a bit on what size tyres you are running, but basically you want the expression

    D * (f/r)

    to be the same, where:

    D=the diameter of the wheel (rim+tyre)
    f=number of teeth on the front
    r=number of teeth on the rear

    You can think of that expression as giving you the diameter of the equivalent sized wheel on a penny farthing for the gear you are in!

    Alternatively, just use Sheldon’s neat gear calculator:

    http://sheldonbrown.com/gears/

    Basically 32/36 with a 56mm tyre on a 29er rim is close enough to 34/36 with a 60mm tyre on a 26″ wheel.

    umop3pisdn
    Member

    Don’t know why people don’t refer to gear inches more often in mtb.

    32 will get you pretty close to the same ratios if you are using the same range of cassette.

    (29-26)/26 = 11%

    34-11%= 30(ish), but 30t is hard to come by as it won’t fit on normal 4 bolt cranks. If you want/need it then I’d get a 32 and a 11-36 (or 12-36) cassette. 32t with whatever your existing cassette is will be aproximately half a gear higher.

    Don’t know why people don’t refer to gear inches more often in mtb.

    Because

    a) it leads to arguments over whether it’s measured as development or as a wehel size (it should be wheel size, development is usualy expressed in metric units)
    b) it’s fairly nominal as unlike road bikes with 23mm tyres, everyone picks a different tyre.
    c) it’s really most relavent on fixed/SS bikes (all my MTB SS’s are 49-50″)

    Premier Icon trusty
    Subscriber

    Quick question to the masses. Was running 1×10 on a 26″ wheeled bike, 34 tooth front ring. Just swapped to a 29″ bike, and again want to go 1×10. What chainring will give me the closest ratio, 32 or 30?

    ta all 😀

    I’ve heard/read that 29″ wheel is roughly worth about 3 teeth on the chainring. I’ve not worked this out myself, but seems to pass the common sense test. I’m running 1×10 on my 29er with a 28 up front (so maybe equivalent to a 31 on a 26er) and the usual 11 – 36 cassette out back. It is low enough for me to tackle any steep climb but I do suffer a bit on the high end when i’m on a smooth track/road descent, but in those situations i’m not looking to power my way down. So all in all it gives me more than enough range for off road riding. I could probaly go for a 32T up front, but what’s the point? I’d rather have the extra low gear to go into if I feel I need/want it.

    bikeneil
    Member

    I don’t know why people get so obsessed with gear ratios. Just try a 34 and if it’s too hard try a 32 etc…

    Of course , that would be so much easier than having a formula to work out how many inches your current set up is and then replicate that .

    Premier Icon trusty
    Subscriber

    Cheers all, didn’t think I’d get any answers! Looks like the equivalent is in between 30 and 32, ta.

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