Originally Posted by 79pmooney

How do you mash at 170 rpm? I find that at those RPMs, all I can do is spin. (I've been close to 50 mph many years ago riding fixed on a 42-17. That is much faster than 170 rpm. Don't believe me? Ride down Joaquin Miller into Oakland, CA from Skyline. Do it without resisting the pedals. But pay up your health and life insurances before you start.)

The OP's gear is 42/16 X 27 = 71 inches. 170 rpm = 32 mph. (A very useful rule of thumb for in-you-head gear calculations like you might do while riding: 42-17 on a normal 700c wheel ~= 67' gear ~= 20 mph and 100 RPM.)

Ben