Bicycle Gear Calculator The link is for a mini-program that graphically shows the effect of changes in gearing in gear inches. For example, my bike is a triple with a small chain ring in front of 26T. The cassette has a largest gear of 30T. This produces gear inches of about 22. It is very easy, in the program, to slide various gears and chain rings around to get the right combination. He will get stronger and eventually you will be back asking about gear changes for yourself.