I checked and according to the vintage trek site this is a 24. My roadbike size is 56cm and I believe that makes me size 22.5. I don't have any standover room at all. It is touching but not uncomfortable. by standing both bikes side by side seat height is same after adjustment, height of bars same, distance from seat to handle bars the 620 is negligibly longer almost the same. From seat to pedals positioned horizontally is same. I guess I will just start taking it on longer rides and see how it feels.