Singlespeed & Fixed Gear - Thoughts on this setup (crank arm length+chainring)
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06-03-11, 12:43 AM
This is the setup I am currently thinking of putting on my new build: 44t Sugino chainring with 140mm crank arms. 15t cog in the rear. Why this setup? Because I'm short. Like 4"10 short. My only concern is that this might be a bit difficult to pedal because it's harder to generate torque with such a short crank arm length. What are thoughts on this? Should I go 150mm instead? It's only .5" gain . . .
06-03-11, 01:32 AM
Assuming you're using 700c wheels, 44/15 is not going to be an easy ratio and your 140mm cranks might take some muscle to get the bike rolling.
Is there any way you can try out the cranks before you buy them?
06-03-11, 08:46 AM
Forgot to mention i'm running 650 wheels. The GI is around 72 so it's pretty moderate - I might switch out the rear to a 16t... SF is hilly!
06-03-11, 08:48 AM
72gi with 650 wheels and a 140mm cranks still seems like a pretty wonky setup.
06-03-11, 09:12 AM
Try using this crank arm length calculator as a starting point >>> http://www.machinehead-software.co.uk/bike/cranks/cyclist_crank_length_calculator.html
Note that it's based entirely on your leg (inseam) length, rather than overall height.
As to choice of gearing, I'd be inclined to go a lot lower than 72 gi given your riding conditions, regardless of crank arm length.
You can also use sheldon brown's gain inch system to compare everything, it includes crank arm length in its comparisson factor
06-03-11, 05:01 PM
I measured my inseam and the calculator said 143 for crank arm length. Meh.
06-11-11, 12:31 PM
Riding fixed in SF @ 72 GI = Character building to the max!
I agree with other posts - you should stay in the low to mid 60's given the shorter crank length (less leverage) and what I would guess is a very modest amount of weight you would be able to apply when standing.
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