Bike sizing issue - Page 2

Seattube angle is an indirect measurement of your femur length and is important when trying to start with that small 'c' constant of KOPS(knee over pedal spindle). In some cases, a too steep or too shallow seat tube angle will prevent this regardless of seatpost design, setback or no. As an example, when I was riding a 72.5 degree seat tube DeRosa, in size '58', for me to ride a Colnago, I had to go up 2 sizes, to get a shallow enough seat tube. AND, when trying to get KOPS, moving the seat forward or aft also effectively lengthens or shortens the top tube. So, I would say that angle is important.

I agree about seat tube angle and top tube length, and I also agree that that head tube length is the third important measurement for fit. A bicycle with too many spacers looks a bit odd, and is not as strong.
It is a strange irony that just about the very least important measurement is used to define the size of a bicycle frame.

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