45% front wheel / 55% rear wheel weight distribution: That's another familiar rule of thumb. Actually, the range is (40-45% front and 55-60% rear). While we use this rule of thumb, there has been no systematic research to back it up. Not only that, people rarely actually measure it, let alone testing it against real world experiences.
With all the money spent on wind tunnel testing, structural modeling and other bike performance topics, I'm surprised at how little has come out on this topic. For those who think that the big Tour teams keep it a secret, the fact that race bike weight distribution hasn't changed much in the past 20 years means that either:
a> nobody's studied it.
b> somebody's studied it and found that there aren't any changes worth making.
Here's a fun link to a weight distribution applet: http://www.ibiblio.org/links/devmodules ... heory.html
The applet was designed as part of Rensselaer Polytechnic Institute's engineering program - more as an illustration than anything else.