Originally Posted by
desuism
I know I'm nit picking but you do realize you divide to find mph, not multiply. That's why you might sometimes see mi/h, as in, division.
(Also, according to you you'd end up going 0.34 mph)
No, the calculation by colombo is correct and if you look at the units you'll see that the revs and minutes cancel out since they appear in both numerator and denominator and the only units left are miles in the numerator and hours in the denominator; i.e. miles/hour. Of course actually achieving a cadence of 4000 rpm is likely to prove rather difficult - and especially so in a 4:1 gear ratio (108 gear inches). Good luck with that.