Originally Posted by zacked
Please assimilate this advice as you would any from a stranger on the internet.
Why does the truth make me laugh?
Huh?
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A friend has a very nice fixie conversion.
He got pedal strike with 175mm cranks.
A frame designed for fixed gear has a much higher bottom bracket, and this reduces the probability of pedal strike almost to zero.
Let's see.
Yesterday, Pi Day.
3/14
What did we learn from Pi Day?
A 175mm crank has a diameter of 350mm and a 165mm crank has a diameter of 330mm (did that in my head...better check it).
350 X 3.141592 equals a larger number than 330 X 3.141592.
What else?
Distance equals Time times Rate.
D = TR.
In one case, the pedal and the foot on the pedal must travel 350 X 3.141592 every time the crank goes around, and, in the other case, the pedal and the foot on the pedal must travel 330 X 3.141592 every time the crank goes around.
If the crank must go around in its circle 120 times in a minute in order for the bicycle to go as fast as the rider wants it to go, how much further will the foot on the 175mm crank travel in a minute than will the foot on a 165mm crank in the same minute?
Or, given that the foot on the pedal can only travel so far in a minute, how many more revolutions per minute would a 165mm crank make, for the same foot speed, than would a 175mm crank?