Originally Posted by
lostarchitect
For some people that chart doesn't work. For instance if you're like me. I'm between 5'9" and 5'10", but I have short legs ( approx 30" inseam). According to the chart I should ride about a 56 but I have not yet found a 56 that fit. It's more like 53 and sometimes even they are tall.
The chart is only a starting point, and assumes a stock frame in terms of the TT to ST ratio; IOW, a frame built for pretty normal body proportions. I would think that at 5'9" (69") with a 30" leg length, a 53cm c-t-t frame with stock TT to ST ratio would feel rather cramped because the top tube of a stock 53cm frame would be too short for your relatively long torso/arms. Bear in mind that the frame size used in the chart is the seat tube length from the crank center to the top of the seat tube. A 56 on the chart would be a 53 or 54 if the frame size is measured center-to-center.