I use a 40x17 on my single speed road bike(freewheel). It has the perfect combintaion of climbing ability and flat speed. I can sprint up to pretty fast(no computer or anything). On my beater fixed commuter, its a 39x14, and climbing is rough on it, but I get more speed on the flats of Bowling Green. You mostly tailor the bike to your needs. A 53t ring will make climbing almost impossible, in my opinion