Aralo wrote:This time, they had their OWN test device. They built their own "treadmill like" device to measure the rolling resistance. No, they didn't go to Conti this time.
... They also noted that because of their new test setup (which basically simulated real world road better than the previously used roll) the worse and good tires are closer together than before. Before they were around 20W better, now only around 10W.
Well, duh (that's directed at Tour, not you ;-)
When you measure Crr on a roller drum, the power required to deform the contact patch from the curved contact is higher than it would be from a flat surface at the same loading. Luckily, there are equations that allow one to easily equate a curved roller value to a "flat surface" value. That's what I do when I measure on rollers. For example, the power required from a tire on a 4.5" diameter roller is ~5-6X what it would be for the same speed and loading on a flat surface.
That's also why I call rollers "Crr amplifiers" ;-)
BTW, the VIttoria Diamante Radiale is an "interesting" tire. The supposed benefit of the "more radial" construction (it's not a true radial) is potentially lower Crr. I got one of these tires and tested it on my rollers and the tread compound is VERY soft and the tire is a real dog. It's also quite "squirrely" on the road. Fairly unsettling, in fact...
It would be interesting to see their treadmill setup. I wonder how they account for the extra drag from however they keep the surface "flat"? Sounds like they could've saved themselves some work and just used the roller-to-flat equations :-/