upping the gears

Discussion in 'Bicycle Mechanics and Repairs' started by jonny jeez, 17 May 2010.

  1. I find that I am "spinning" out on faster sections of my daily ride and want to find a way to increase the gearing on my bike…..I'm afraid that gearing really confuses me and being able to know what gearing I have…or how to up-rate it, is a mystery to me.

    I ride an old MTB, so I guess the gearing is kind of "alpine". Can I just buy a larger chain-ring or do I need to look at replacing cassettes etc?

    I top out at exactly 26mph until I literally "roll" up into the 30's (I'd like to pedal and get a little more out of the downhill sections) but start to pedal pretty fast (uncomfortably so) at around 24…

    I prefer riding with a slow cadence but with more pressure on my legs (rather than pedalling fast with low resistance) so am happy to look at a more demanding "top end", after all I have 20 other gears to fall back on if I want to go up really steep bits.

    Can anyone suggest a simple solution
     
  2. Globalti

    Globalti Legendary Member

    You're ready for a road bike.
     
  3. GrasB

    GrasB Veteran

    Location:
    Nr Cambridge
    Do you know what chainrings tooth count you have now? Often this is stamped or printed on the chainrings them selves, from there we can give you more of a clue.
     
  4. A lot of MTB chainsets have either 42 or 44 teeth on the largest ring - as I found out while trying to replace my 48 toother recently. As I had an 3211 cassette already and some long downhill sections on my commute, staying with 48t was well worth it and really the only way of keeping the gearing reasonably high.

    You may be able to get a bigger ring for your chainset, but make sure your front mech can take the (presumed) increase in size.
     
  5. HaloJ

    HaloJ Rabid cycle nut

    Location:
    Watford
    N + 1 :tongue::tongue:
     
  6. RedBike

    RedBike New Member

    Location:
    Beside the road
    26mph sounds about right.

    A 26" wheel with a 1.9" tyre has a circumference of 2089mm
    Im GUESSING an old mtb has a 42t chainring and a 14t sprocket.
    This gives you a ratio of 42/14 = 3
    Pedalling at 100rpm, the wheel will rotate 3x100 in one minute or 18,000 time/hr.
    Covering 2.089m x 18,000 = 37602m (37.6km/h) about 24mph

    The trouble is *IF* your bike has a freewheel instead of a cassette then you'll be very lucky to find a freewheel with a smaller sprocket than a 14t.
    So your only real option would be to fit a 48t chainring.

    This gives you a ratio of 48/14 = 3.42
    100rpm => 20520 rotations /hr
    2.089m x20520/1000 = 42.9km/h ~27mph
     
  7. OP
    OP
    jonny jeez

    jonny jeez Guru

    Thanks all.

    I shall go "count the teeth"....joy.

    Redbike, thats the most detailed explanation, thanks. from what you say I can only expect to gain a few MPH (24 - 27) from upping the chain ring, so perhaps this would be a waste of cash.

    Hmmmm trying to avoid N+1 as I really love ol' chitty
     
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