Originally Posted by
bruce19
Maybe I'm a traditionalist. Back in the day frame size was approximated by inseam. Per people like Greg LeMond and his coach Cyrille Guimard. And others. For example....I am (now) 5'9" with a 32.25" inseam. A friend is 6' with the same 32.25" inseam. We both ride a 54-55 cm frame. His upper body and reach are longer than mine so he has a longer stem. That is not to say that we can't ride a range of frame sizes. But, IMO, inseam is a better prediction of ideal frame size. Has worked well for me over the pat 40 or so years.
Lemond's recommendation works great - if you have average proportions. Your friends torso is 3" longer than yours, but I'm willing to bet that he isn't using a stem 7cm longer than you are. Most people with his proportions would be better off on a frame that has a little less standover but a reasonable amount of reach. And he has the reach of someone closer to 6'3". That's why the best compromise is to spread the problem between seat tube and top tube rather than take someone with a 6'3" person's torso and put them on a bike with a 5'8" persons reach.