Originally Posted by
Kontact
I don't see how you'd come to that conclusion. Frame size is like dress size - it is an overall size that attempts to cover both seat height and reach. You're suggesting that it is better to size something like that by only paying attention to one isolated part of the anatomy rather than the larger picture. Women don't size dresses by only looking at leg length, and I don't see why you'd size a bike that way. The "traditional" sizing advice wouldn't be used if someone fails to have a "traditional" build.
It would be interesting to see a picture of your 6' tall friend with the long torso crammed onto his 54. Does he have a 170mm stem?
You lose the argument to Bruce, because frame reach can be changed relatively easily with stem size but frame height aka head tube height aka effective seat tube height which dictates saddle to bar drop
has much less adjustability.
This is why for 50 years, it is seat post length or effective seat post length that is used for a single metric of frame size which only indirectly corresponds to a person's height.
Also, your reference of a person's height has no direct correlation of stand over which can rule out a given frame size relative to a person's height.
Truthfully, a person's height doesn't matter at all. What matters is a person's leg length and person's torso length and how aggressive a person rides.
More enlightened fitters however never use a single metric to choose a given frame and therefore the whole discussion is somewhat meaningless.