Originally Posted by
John E
Interesting leg length / height / frame size chart. At 5-8 with a 30" trouser inseam, it says I should be riding a 54 to 56cm frame. The Capo and the Bianchi are 55cm C-T, and I they fit me perfectly. The Peugeot is 53.5cm, but very long in the top tube.
That isn't surprising. The ratio of top tube length to seat tube length for stock (not custom) frames is based on the individual manufacturers' experiences with the body proportions (torso length and arm length to leg length ratio) of average riders of different overall height. Some manufacturers bias their stock frames with longer top tubes relative to the seat tube length, while other manufacturers bias their stock frames with relatively shorter top tubes.
The chart in the post above is generic and is based on industry averages, so it should be used as a sizing guide just to get a rider in the ballpark rather than as a hard and fast rule for frame sizing.