My bike is a Masi Gran Criterium S. It has a sloping top tube and has no indication as to frame size. Back in the day I rode a Maza 54 cm C to C frame based on a variety of fitment guides in various books and magazines and my 32.5" inseam. Seemed to work just fine. Then I gave up riding for 8 yrs. When I came back to riding, bikes were no longer steel, there were triple cranks and sloping top tubes. Gone were my beloved Athena friction shifters. The Masi was a 60th birthday present from my gf and after 5 yrs. of riding it I still love the bike. Of course, since I had lost an inch of height (all in my upper body I assume) I had to replace the 110 mm stem with a 100 mm stem. Then I got curious. "What is the size of my bike?" So, I tried to measure it using the "virtual" lines people tell me are appropriate. Found a level floor and using a builder's level measured the virtual TT length and seat tube. Strangely both measurements came out 58 cm C to C. That seems pretty big to me. Am I doing something wrong with my measurements?