You can look up any number of manufacturers rev/mile for a given size.
You will find they tend to group together in a range and then you will
see that the Miata Tire Toy program calculates a value for that size
that falls outside of that group. You could say that none of the tire
companies can count or measure but I would say the Miata Tire Toy
program makes erroneous assumptions and then gives false results.

Also, axle center to ground distance is a poor way to measure tires for
revs/mile purposes as inflation pressure affects that static measurement
to an extent that greatly exceeds its effect on true revs/mile while
rotating.

Mark

John Bange wrote:

>
> I would love to trust the manufacturer's quoted numbers, but when the Revs
> per Mils and the diameter they state don't match, it's hard to take them
> completely seriously. I suspect they might use the largest possible
> diameter, and the smallest possible rolling radius. Given that, I tend to
> use the mathematical number initially, and then actual physical measurement
> after they're on the vehicle (axle center to ground, and GPS mileage vs
> miles clocked that assume 805 RPM).
>
> --
> John Bange
>