On Tuesday, February 18, 2020 at 2:21:40 AM UTC-8, wrote:
On Tuesday, February 18, 2020 at 9:32:31 AM UTC+1, John B. wrote:

Of course there is a power loss but it is not the friction between the
generator roller and the tire wall.

Of course there is friction between the generator roller and the tire because the direction of the circumferential speed of the roller is not exactly aligned with that of the tire.

Lou

I suppose you're correct since you are on a tire that has a changing diameter while the roller on the generator has a fixed diameter. But I always had the idea that the real losses were from the displacement of the sidewall.