Originally Posted by
Fentuz
No, you took a screenshot and did not give the full picture which is in the video. They do show that for a given tyre, as you up in size, you loose Watts.
Then they explained they tried something different, a different system which is giving better results by luck and they don't know why.
Eric F comment is in line which what is expected however, in this very specific situation, there is something lucky. So does a one off anomaly enough to refute conventional wisdom?
They clearly say the data are repeatable and not explainable; a single set of data for a single product does not make EricF's statement false. That said, more work should be done to understand the data and therefore develop better large volume tyres with good aero and low rolling resistance.
The full picture was contained in my original response. Your additional context has added no relevant additional information.
Wider and knobbier tires will not always have more aerodynamic drag. This is the result of the experiment, it has upended what was previously known and what was once a true statement is false. that's the whole point of such work. Tire width and design are not constrained by "conventional wisdom" - as if that phrase had any relevance to aerodynamics in the first place.
We also don't need to appeal to "luck". There is a very small pool of XC size tires that have ever seen the inside of a wind tunnel. We don't have the data to say if the Race King is an anomaly or not. It's entirely possible that as tires pass a certain width, and with certain knob design, the knobs act as turbulator strips (or perhaps vortex generators) and keep air separated from the sidewall (and possibly the tread), effectively reducing both frontal area and cross section density and thus reducing drag. Close to, or perhaps the same as sailing effect. We know that mathematical models of fenders do something similar and theoretically provide similar benefits, within the model speed bounds.
For anyone really keyed in, this wind tunnel experiment argument is basically a re-hash of the wide tire argument. Think back to all the arguments about how and why wide tires couldn't be as fast as narrower tires and how that turned out. Lesson there.