it has been years since i figured out "gear inchs" for my bikes. isn't it like chainring x wheel divided by ? if anyone has the formula, id appreciate it. also, is their a different number i plug in for wheel size if i calculate bikes with 26x1.95/2.125 tires vs 26x1 3/8 and 700c wheels. and what does gear inchs actually measure? distance traveled on one rev? thanks