Originally Posted by
Campag4life
With respect and no quibble it works for you, it may not apply to others. But yes, old stand by of .667 x inseam will fit a large population of riders. But the landscape is quite a bit different today with un-square frame proportions aka endurance geometry frames many seek for a bit more upright position. Skewing of this proportionality may work well for a given rider or may work against them...depending on torso to leg length ratio. So selecting frame size today in particular with all the different geometries available is a slippery slope. But never been a better time to buy a bike today with all the frame geometry options. Issue is...sorting through the complexity what may work best for a given rider.
As an example, I am longer of inseam and shorter of torso. A Roubaix will fit me identically to a Tarmac for another rider the same height with opposite proportions aka long torso and short inseam.
Just to clarify....I have no issues with a professional bike fit. I have done several and would do it again. What I have found is that they put me pretty much where my estimate would be. For me, they are great for getting at details. I was just trying to give the OP an idea of how to determine if a particular frame size was "workable" so to speak. I ride both a 58 Masi Gran Criterium S and a 55 Guru Sidero (steel) and both work really well for me. The 55 is optimal and required little modification. The 58 w/ shorter stem and a couple other tweaks is just as comfortable. I agree that individual proportions will drive frame size. That's the place to start.