Originally Posted by Doug Fattic

The standard way a bicycle frame size is measured today is the length of the seat tube in centimeters starting from the center of the bottom bracket shell to the center of the seat tube/top tube junction. This is how most people understand classic era frames (with level or almost level top tubes) are measured. In the old days when Americans and British were unfamiliar with the metric system and described a frame size in inches, they were measured from the center of BB to the top of the seat lug. Well the problem is that the "top" of the seat lug varied. Seat lug tops had different lengths. So where exactly is the "top" of the lug? For example the 22 1/2" Hetchins I bought from Alf in 1969 is about 1/4" smaller than other 22 1/2" British frames. They didn't always measure to the very tippy top. Eventually it became the preference to describe a frame size in centimeters measuring to a very precise ST/TT junction. This is the way American frame making fixtures are measured and so it became the standard.

My explanation that my Masi was described by Faliero as being a 58 but when actually measured precisely c-c is almost 559mm should allow you to figure out what Masi frame size you actually need. You were correct in saying a Masi size is about 2 centimeters bigger than how we standardly measure level top tube frames today. Again letting you know that my 58 cm Masi with tubular tires has a straddle height of 83 centimeters can help you figure out what frame size you need if you are using straddle height to help determine your Masi frame size.

Another way to help determine frame size is based on the BB to top of saddle length and how much drop your handlebars are below your saddle. But we are getting into the weeds here. BTW, one of my framebuilding colleagues wanted to buy a 54 cm Masi because it was the 1st bicycle he raced. Eventually he had to make one himself because he could never find the 54 at a price he could afford.