Hey rick, sorry for the delay in getting back to you. I'm 5"11 3/4 with relatively "normal" reach and inseam (33"). I ride the Lapierre Sensium in 55. I'm not sure why they call it a 55 though, as the effective top tube is 56.5. My guess is the 55 will be right for you. Have you compared the geometry charts of both bikes (the Giant and the Lapierre). the Xelius, especially the 400 FDJ model is a beautiful bike, and you won't see many, if any, others like it on the road when you're riding, if that means anything to you....if you want a second opinion, you should call Brad at LapierreToronto. It's a new store and they sell nothing but Lapierre...