To get a constant horizontal speed, a small-radius wheel must turn faster than a large-radius wheel. For a constant turn rate & rim mass, a small-radius wheel w

To get a constant horizontal speed, a small-radius wheel must turn faster than a large-radius wheel. For a constant turn rate & rim mass, a small-radius wheel will have less energy than a large-radius one. I suspect (given the article's statement doesn't depend on the wheel radius) that these precisely cancel, but I haven't done the math to prove it.