I love that I've been cycling for 14 years now and am still asking the most basic question.
I currently have a 54 cm road bike that has 4 inches of exposed seat post (to the bottom of the seat) and I have a 140 mm stem (I like it streched out). The stem is a quill stem and is close to the bottom of its height adjustment. The frame appears to be a little large by looks alone, but it fits just fine. I want to build a nashbar touring frame in the future and am wondering if a 52 cm frame might fit better? The lack of seat post exposed and the lowness of the stem seem to point out that a 52 cm would fit, but my preference for a longer stem would point to keeping a 54 cm frame. The bike would be used for commuting and general abuse, with a little bit of touring. (the 54 cm nashbar frame and my specialized epic seem to be close or exact in size in seat tube and top tube)