Originally Posted by
Jeff Wills
“Different” in that a 10mm longer crank puts the pedal 10mm closer to the ground. The common 2.5mm (or 2%) increment is almost irrelevant when people vary 20% in height.
There’s a fair amount of experimentation with short cranks (140mm to 160mm) in the recumbent bike and trike community. Mostly this is done to facilitate faster spin and lower stress on old, creaky knees.
But that doesn't have much to do with pedal strikes. The range might be 140 to 180, but since road bikes are built for 170 or longer, it isn't like the lower end of the range matters.
And then there's the fact that pedals have increased cornering clearance since the late '80s, so cornering with 180s now is like riding Campy quill pedals in the early '80s.
Just to put some numbers to this, my hypothetical bicycle has pedal clearance to 29.7 degrees with 170 cranks. Cornering drops by 2.5 degrees to 27.2 with 180s. That's the same amount if you use pedals that are 2cm longer. I don't think 2.5 degrees is significant compared to what people believe they are getting out of more suitable crank lengths.
And then if you have gotten on board with big tires, your 35c tires make up for 180 cranks compared to 25c.