Originally Posted by
General Geoff
When it comes to touring bikes, 18 gear inches is considered a good granny gear. Gear inches is how many inches you travel forward for one complete pedal revolution. Even with a 10/36 and 30/43 setup, your lowest gear would afford you 22 gear inches given a 700c/32 wheel/tire combo. You should go lower. Aim for that 18 gear-inch number with your lowest ratio..
Gear inches is the equivalent wheel diameter with 1;1 drive. You'll go a little more than 3 times that far for each rotation of the pedals.
Think back to the high wheeler days. A bigger wheel meant you could go faster assuming your legs were long enough to turn the pedals. When chain drive "safety bicycles" were invented sellers needed a way to compare the gear ratio with the high wheelers that people were used to.