Good lord, what do they teach you at college? 1 inch = 25.4mm. 25 is
near enough.
So 5 inches = 125 mm
6 inches = 150 mm
Cranks of 150 mm or more are generally considered "long".
Cranks of 110 mm or less are generally considered "short".
Standard sizes are 80, 90, 102, 110, 114, 125, 140, 150, 165, 170 mm.
There may be others (I have some 89s and some 127s somewhere).
What is a good size for riding a 24 fast on the flat? I have 114s on
my *28 *and ride it off road including hills. I have done so on 102s.
125s should be easy on a 24 with only a minimum of practice. 114s or
110s should make it go like poo of a spade. I used to road ride my old
24 on 102s.
But hey, Aspenmike - who is a better man than I - swears by long cranks
and rides his Coker on 170s, whereas I use 150s. The moral: there is
no right answer.
The mechanics are very easy to understand, though.
Long cranks give you more leverage. This means it is easier to control
the unicycle on a down hill, and easier to power up a steep hill. In
my experience, the downhill control is the most noticeable bit.
However, short cranks allow you to pedal faster, because your feet only
have to go round in a small circle instead of a big one. You get more
speed, at the loss of some control.
What is the correct balance between control and speed? One school of
thought is that it is a bad idea to use a shorter crank than you can
comfortably idle.
Another school of thought is that if you can learn to pedal fast with
long cranks, you get the best of both worlds - the ability to go fast,
but with as much torque and control as you need at slow speed or on
hills.
A simple answer: try some 125mm (5 inch) cranks or, if you are feeling
bold, some 114s.
--
Mikefule
"The world is Hell, and men are on the one hand the tormented souls, and
on the other the devils in it."
Arthur "Cheery" Schopenhauer
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