Originally Posted by
arfer1
Thanks noglider. If I understand the formula you used, you take the number of teeth on the smallest crank, and divide that by the number of teeth on the largest ring on the freewheel, and multiply that by the size of the wheel to get gear inches. Is that correct?
Correct. And by size of the wheel, if you're using 700c, that equals 622 + 2*tire height, so assuming 700x28's, then 622+2(28)/25.4 (convert to inches) = 26.69". 28/21*26.69 = 35.59 gear inches.
noglider just rounded to 27, which would be a be a 700x32.
Now I changed out my wheelset from a 27" to a 700c. Has your bike been changed to 700c? That will allow for a slightly wider/taller tire. I changed out mine primarily for fenders. I forgot about that in my sample calculation.