I'm looking at buying a road bike online ebay, and I'm VERY confused by the numbering.
What is a good guide for the length from the crank to the top tube that corresponds to the rider's height?
My inseam length is 78cm, which according to some websites mean i should have a 520 mm roadie seat post length (c to c). But most bikes I find are around 560 - 580mm (c to c), and some of the riders of those bikes are shorter than me!
Seems strange that it's so difficult to find a good frame size given I'm average height (1.74m)...Am I calculating something wrongly?