rruff wrote:
I'm not concerned about mimicking asphalt. The apparatus that holds the wheel has a sliding fit with one tube inside another (friction). I'm not sure how the load is applied, but as I recall that was not a simple weight, but rather a load cell of some kind. And measuring motor input and subtracting an efficiency is not the best way to determine power. There are too many opportunities for random errors and a drift in calibration.
The "consistency of numbers compared to other sources" argument doesn't hold weight. Errors big enough to be obvious in that respect would need to be pretty huge. Since he is testing and comparing tires over a span of years, I'd like to know if he gets the same results with the same tires over that span. For instance does the GP4000 measured now have the same Crr as 4 years ago?
That would be nice, but how do you propose he preserve the tire over a 4 year period from environmental changes? Bottom line, I trust his testing and have had good results picking tires from his data. If you are looking for absolute verified perfection, good luck :-) BTW- he has many results posted on his site of the same tire used in multiple tests, you can certainly review those and decide if it meets your standards. If not, and if you have a better source for more reliable tire data, I would greatly appreciate you sharing, as would many other on ST