Hi everyone,
I know this is a kind of an old thread, but hopefully my lunacy can help someone else.
Basically, I went though this same issue with my 24" cruiser. I'm 5'10" with a 30" inseam. My bike came with 180 cranks and 41/18 gearing. This felt pretty good around the neighborhood and seemed to "take off" pretty quickly from a start, but when I got up to speed, I felt like I was literally falling off of the cranks and couldn't spin them as I recalled from my first stint racing bmx back in the late 70s. After trying two different gears (39/17 and 40/17), I decided to try some 175mm cranks with the 40/17, since that was closest to what I used BITD on a 20". Well, I don't know if I'm truly faster with them, but I feel like I can actually spin the 175s at speed...they just feel faster to me.
So lesson learned: I'd say make sure you use cranks that match your build, then dial in the gears. And don't think that big cranks equal speed/power. What matters most is your ability to move those cranks in a circle as efficiently as possible.
Cheers,
brad