Originally Posted by
tFUnK
Nice, that's probably the best fixed/single gear specific calculator i've seen.
It really varies between riders and situations what feels like spinning out. For me, 130rpm on the track feels like 160 on a downhill. Also depends if you've got brakes, how tight your clips/shoes are, etc.
I've spun 180rpm downhill, early on in a ride to death valley, but my achilles were in pain at the end of the ride. 38mph is probably faster than one should go on a 42x16