Comment was made a few posts up about a bike 3.5# lighter than the other would be faster. In light of the OP and questions, I don't think that plays out. Like the poster about here said, he puts two water bottles on his bike that weight that. He also mentioned another point that I would as well....for many clydes the difference in between what would be considered lightweight and average, between the weight of bikes, is easily water retention or a full belly.
When you take into consideration the average frontal area, etc. mentioned in OP I just don't see how a difference of a few pounds makes any significant (speed) difference to riders like myself.
edit- just in the interest of "hearing myself talk" and by way of explaination on my above comments, I will proceed with some antecdotal evidence....When I moved to the new bike, which by all means should have been faster than the old. It started off 11 lbs lighter than the Al framed Trek. I noted a small and short increase in my average times which should likely be considered placebo effect. What I did notice was a significant increase in the mileage ridden. I figure that was a combination of the weight, correct sizing (comfort), and the "buffering" effect of the carbon frame (comfort).
Last edited by Juan Foote; 12-11-11 at 09:48 AM.