FastMover — Thanks for posting your formulas. Having examined them and compared them with mine, I now believe that the error is not yours but mine! It seems to be simply the result of my using the wrong (i.e., "unloaded") radius for the TCH's tires, instead of the correct (i.e., "loaded," what you call "static") radius, in my formulas. This relatively small error is enough to throw out my numbers significantly. I'll report back once I've checked a bit more, but I think I now have this discrepancy sorted out.

Incidentally, the behavior of the tire as it rolls is strange indeed! If r0 is its unloaded radius, and r1 its loaded radius (r1 < r0), then the car moves forward a distance of 2*pi*r1 for each revolution of the wheel, whereas the circumference of the tread is the somewhat larger number 2*pi*r0. One would naively think that the car must move forward by a distance equal to the circumference of the tread, but this isn't so! The tire must thus continuously deform as it rotates to accommodate this difference. This deformation must be a primary cause of tire rolling resistance. Am I correct?

Stan