Originally Posted by
shoota
It's an old wive's tale that *might* have had some credence back when all road bikes were essentially the same geo. It's complete baloney now.
You are correct that is is not a precise measure, but IMO, it is still a pretty good rule of thumb for most people - provided you go in with the realization that it is just an approximation or a starting point, and some small tweaks may be required. I use it as a way to guess if the fit is more or less in the right ballpark.
OP, i am 183 with a 34" inseam and i ride best on a 56 - you and i both have longer legs and shorter torsos, and would be better suited by a taller/narrower bike than a longer/lower one. While i ride a 130mm stem now, i started out with a 90mm. If you have a 58, you are likely a bit too far forwards, especially if it is your first drop bar bike. Can you raise the bars a little? That will help, as will using a shorter stem. You can also get a compact, low-reach handlebar.
A 1 size differential is fairly easy to correct for (my first road bike was a whopping 60!).