Originally Posted by merlinextraligh

Well I can tell you from calculations from actual data that the difference is about 1.8mph for an average rider.

Go to Kreuzotter, http://www.kreuzotter.de/english/espeed.htm, use the default weight, height and power output (160 watts). Hold the tires, and bicycle weight constant, and the difference comes out to 1.8mph.

There's a reason that people that are trying to go fast on bicycles do it with drop bars ( aero bars in certain circumstances) and not with flat bars.

And the comment which you cherry picked is in the context of a high end racing frame with deep sectioned carbon wheels with flat bars being used to race.