Originally Posted by
SHBR
How fast does the OP need to go?
42T X 12T 700C X 23MM = 40KM/HR @ 90 RPM & 52KM/HR @ 120RPM
I use a triple crank with a single speed wheel, 24/38/50T X 18T.
I spin out at 50KM/HR, more than sufficient for my (flat terrain) needs.
That's an interesting and unusual set up you're running there, SHBR. Do you have a rear derailer to maintain chain tension?
I've spun my 42-12 over 35 mph many times. 37 at least once. The only way I could justify any taller gears is if I had some long descents, which I don't. Maybe the OP does.
I understand that not all riders care to, or even can, spin these higher RPM's.