Originally Posted by
3alarmer
...as a physical model, there are many places where energy is lost on a bicycle. Tires, rolling resistance, aero resistance because we don't ride in a vacuum, general friction losses all come to mind. I'm not arguing your general point that in a perfected theoretical model, mass continues to go in the same direction, and at the same speed, once you get it moving. I'm just saying that in this particular case that we started out discussing, (a 112 mile tri race over rolling countryside, with 20-30 mph gusting winds), it's a much more complicated picture of how often you need to introduce new accelerative force into the system.
Well no, energy is not lost, it's just turned into heat.
But we were talking about rims (I thought). There's a little bit of energy lost due to atmospheric resistance on the surface of a rotating rim, and the deeper the rim, the more is lost, but that's a very small amount of loss that's only due to rotation. Vastly more is lost to the spokes just from rotation. What you're saying is true, but it has nothing to do with rim weight. In all the cases you point out, less energy is lost to an aero rim, no matter its weight. Though one must also point out that next to the losses due to the bike and its rider, the contribution of the rims is quite small.