If you are measuring a frames size along seat tube doesn't it give different frames size depending on the angle of the seat tube to the top tube. If it is a 68 degrees versus 74 degrees aren't we describing two different frame sizes. Isn't a better way to measure standover height and top tube length. I am waiting for comments. Charles Nighbor PS a perfect 57cm frame size no a prefect 56cm frame size or is it a 58cm frame size. Walnut Creek, CA USA