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Fixed TT gearing

maddmattmaddmatt Posts: 166
edited March 2010 in Amateur race
Could anyone recommend a good gearing for TT bearing in mind I'm 17 and will be racing in the Northern region?

And whether it's a good idea to run a 3/32 drivetrain as opposed to a 1/8 ?

Thanks in Advance.

Posts

  • John.TJohn.T Posts: 3,698
    82" to 85" should be reasonable. I would not go higher until you have tried this. You can do pretty good times on lower gears. I did a 1-1-30 for a 25 on 71" back in the 60s and medium gear (72") ones are won well under the hour.
  • Assuming the course is a fairly flat one, you can work out which gear ratio to use based on the length of the course, your typical cadence, and the time you expect to achieve.

    eg if you expect to do a 10mile (16.1km) in 23 minutes with a cadence of 100rpm:

    16.1km = 16100m
    circumference of a 700x23mm wheel = 2.1m
    thats 7667 wheel revs for the entire course
    if you do the course in 23mins the rear wheel rotates at 333 rpm
    if you pedal at 100 rpm then you need a gear development of 3.33 - eg 50x15 (90")

    Ideal cadence will vary person to person 100 rpm was just an example. You should have a feel for your own cadence from your training rides but err on the high side as you dont want to be overgeared - you need to be able to to cope with headwinds and changes in gradient.




    I'd go for 1/8" drivetrain as 3/32 chains are designed for use with gears so are more flexable side to side for shifting, therefore more likely to unship on fixed.
  • Monty DogMonty Dog Posts: 20,614
    Yup, gearing depends on fitness, prefered cadence and the course itself. I generally ride 50x16 - my local course has a quite long downhill which you can easily reach 50kph plus and yet I don't want to be overgeared as I have to come back the other way - better to be slightly under-geared than over
    Make mine an Italian, with Campagnolo on the side..
  • Monty DogMonty Dog Posts: 20,614
    Oh - and 3/32" chain is fine as long as your chainline is accurate and tensioned correctly - there's no side load so no reason to unship your chain.
    Make mine an Italian, with Campagnolo on the side..
  • Monty Dog wrote:
    Oh - and 3/32" chain is fine as long as your chainline is accurate and tensioned correctly - there's no side load so no reason to unship your chain.

    Yeah but if you were starting from scratch, there's no reason to choose 3/32 over 1/8" ?
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