Originally Posted by
Brian Ratliff
I don't know about you, but this is also exactly what I would expect, and it has nothing to do with smooth surface vs. real surface. Rollers are very small in diameter compared to... well... a flat surface. Since according to the krietler roller site, there is almost a 100W difference going between 3" dia rollers and 4.5", I would suspect there is a much larger difference going between 4.5" and infinite. Rollers then, are testing what now?
Well now I'm all turned around. First you claim that tires that perform the best on smooth surfaces are likely to perform the worst on rough ones, and now in the face of data to the contrary you say this is what you expected.
The point of the article is not that rolling resistance was higher on the road than the rollers, it's that the rank order on the road was exactly the same as for the smooth rollers; and furthermore, the actual rolling resistance on the road is linear with the value from the rollers. That means roller data can be transformed to road data with a single test of a single tire.