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42*16 V 48*18

robbie the roadierobbie the roadie Posts: 423
edited February 2008 in Road general
In my cycling club two of us mainly ride single speed/fixed in the winter.

I ride 42*16 single speed and he rides 48*18 fixed. Like complete nerds we have whiled away far too much time discussing the merits of either gear, however he strongly believes that 48*18 is the better set up. I have done the sums (assuming there right - see below) and can't really see much in it. To be fair he does seem to be able to motor that bit quicker then me even though wer doing a similar cadence. Have I missed something or is that slightly larger gear really the way to go. If it helps we cycle in the Yorkshire wolds so it's fairly rolling terrain.

42/16 * 27 = 70.8 gear inches

48/18 * 27 = 71.9 gear inches
Cycling - The pastime of spending large sums of money you don't really have on something you don't really need.

Posts

  • BronzieBronzie Posts: 4,927
    Is it possible that there is a mechanical advantage with a bigger chainring as there is more "leverage" on the chain as it's further away from the centre of rotation :?:

    Just a thought.............I paid far too little attention in physics to know if this makes any odds at all :roll:

    I ride 42x17 and my mate 39x16 (both about 66") and I haven't noticed much difference between us other than he is fitter than me.
  • Bronzie wrote:
    Is it possible that there is a mechanical advantage with a bigger chainring as there is more "leverage" on the chain as it's further away from the centre of rotation :?:

    That would make sense to me, lets see if anyone else agrees with this :?:
    Cycling - The pastime of spending large sums of money you don't really have on something you don't really need.
  • LeighBLeighB Posts: 326
    The only advantage to a large sprocket is there is less chain wear due to the load being spread over more teeth.
  • rendorendo Posts: 194
    like letghb says chain wear is the only advantage on larger rings, but you might find the big difference is in the momentum gained by using fixed over singlespeed.
  • rustychiselrustychisel Posts: 3,444
    I see no mechanical advantage in it, 42 x 16 is a very fine gear for fixed. Is he slightly stronger? Better able to adjust to tempo and cadence changes? A little more 'pushy' on hills? The difference, after all, is <2% in raw gearing.
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  • 4candles4candles Posts: 240
    In my cycling club two of us mainly ride single speed/fixed in the winter.

    I ride 42*16 single speed and he rides 48*18 fixed. Like complete nerds we have whiled away far too much time discussing the merits of either gear, however he strongly believes that 48*18 is the better set up. I have done the sums (assuming there right - see below) and can't really see much in it. To be fair he does seem to be able to motor that bit quicker then me even though wer doing a similar cadence. Have I missed something or is that slightly larger gear really the way to go. If it helps we cycle in the Yorkshire wolds so it's fairly rolling terrain.

    42/16 * 27 = 70.8 gear inches

    48/18 * 27 = 71.9 gear inches


    What about tyre size.. ?
    i ride a 42x16 single speed (with a 1/8, half link BMX chain too) with 26mm tyres... but if your both happy with you gearing does it really matter ?

    Also you'll be able to get away quicker and have the advantage in the clubs "long skid competition". !
    lol.
  • don_dondon_don Posts: 1,007
    Tyre size and crank length will make a difference to the actual gear you are both running. There is tons of info on sheldonbrown.com if you are interested, including stuff on energy loss in freewheels vs. fixed etc, etc - a nerd's delight!

    I think the chain wear issue is relevant, but I don't know if there'll be that much in it. One thing about having a smaller chainring is that you can make more profound changes in gear with just a one tooth change at the back (to do with the proportionate size difference between the two, or something, see Sheldon Brown!)
  • I've just up'd from a 42/18 to a 44/18 and can really notice the difference... Wont get to 'nerdie', I'll be way out of my depth!

    I've got a Surly x-check and when I changed to a 44t a few days ago struggled to get the chain the right length - LBS sold me a SRAM chain. With the power-links its either right at the edge of the horizontal drop outs or by adding 2 links the chain becomes to slack... :roll:

    Any ideas ?
    “Look where you want to go. Not where you are going”
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