Originally Posted by
Little Darwin
Gear inches are based on wheel diameter, going back to the day of the large wheeled bicycles. So a gearing of say 26.5 is basically the same as riding an old high wheeler with a 26.5" wheel... not much of a high rider, but that is what it means.
So for a 26.5" wheel, if I remember my geometry right, the circumference (or roll out) would be 26.5 * pi (2 pi r)
So with a 34 x 30 on your bike (29.9 gear inches) the roll-out is approximately 93.9 inches...
Exactly. Gear Inches is equivalent wheel diameter. Development is how far you go in one revolution of the cranks. put a 22 tooth granny on the front and an 11/36 on the back and you'll make it up in 2 hours- in bottom gear.