Originally Posted by
tyrion
I call B.S. on this. (Jobst Brandt knows way more about bikes and engineering than I do, but I think this old usenet post should be challenged.)
I think minute differences in acceleration can make or break competitors at the end of the race. If someone wants to say "it doesn't matter very much" it should be quantified.
The mass at the very edge of a rotating body (e.g. at the edge of the tire on a bicycle wheel) takes equal amounts of energy to accelerate in a straight line and rotationaly. That is to say that there is a 2x contribution to any additional weight at the edge of a wheel while acceleration, as compared to weight on the frame. This effect decreases linearly as the weight gets closer to the center of rotation, meaning that changes in hub weight are nearly the same as changes in weight on the frame. However, you get that energy back unless you use the brakes, and with the case of aero wheels, you likely get much more than that back in reduced drag when pedaling at a steady rate.