FastMover — Thanks for the reference. Now I'm more puzzled than ever!

The Michelin Web site does not appear to give a tire "rolling radius" specification for the Energy MXV4 S8 P215/60 R16 94V tire. It gives a static "overall diameter" of 26.2 inches, which corresponds to the 13.1 inch = 0.3327 m radius that I (incorrectly) used — I rounded this to 0.333 m. It also gives "tire revolutions per mile" of 793 at 45 miles per hour, which translates into a 12.716 inch = 0.3230 m "rolling radius with tractive effort." This is only ~3% smaller than the figure I used. Your figure of 12.052 inches = 0.3061 m for "static radius" corresponds to an even smaller number, which is a more significant ~8% lower than the figure I used. By the way, where did you get your number? Did you actually measure the static radius on one of your own tires? (A quick measurement by me gives a number close to yours.)

So, which number should we agree to use? It would seem that the "rolling radius with tractive effort" is probably the most meaningful. That being the case, the Michelin figure of 12.716 inches = 0.3230 m seems like a better choice than either of our choices. It would be good if we could agree to both use the same number, so that we our predictions are in agreement. This is all about a relatively minor discrepancy, of course, but we might as well get our numbers as accurate and consistent as possible. What do you think?

Stan