I am currently riding a Marin Muirwoods 29er with a 19" frame. How do I find the size I need for a bike with drop bars? Do I go by the top tube length or is it different on road sizing? My effective top tube is 605mm on my current bike but this puts me somewhere around 60cm for frame size which is the biggest frame from many manufacturers so this is not right. I am 68" tall.
I am using it for the street and commuting so there is no racing involved. The attraction of a cyclocross bike is that it looks like they accept 32mm, and maybe larger, tires so the ride should be more cushy. Even though many of them only have two chainrings and sometimes 48 as the largest, I think that might be ok since I'm stopping every few hundred feet anyway. That and San Francisco isn't flat.