Thanks Cox
I am a men with a matematic background so I like to use tols that take into consideration the main elements in a system. The relation between wheel radius and crank length is very important, so I like the gain ration.
Cox, after your detailed explanations I am going to set the gain ratio of my bicycle on 5.5. Where I live I cannot ride flat ground, only up or down hill. If I go up when I leave home, I have a climb of 9 km with a slope of 2 digit degrees. In some bits of the climb the slope is pretty nasty. If I go down when I leave home, the slope is more friendly falling in the single digit degrees and stay like this for 20 km. So the 5.5 gain ratio is a good compromise
PS: the gain ratio is an index without units, so you use it in inches and I use it in meters
