Originally Posted by
terrymorse
OK, yes, there's different rubber used in different spots of some tires.
But even given those multiple rubber compound tires, I'm still not seeing how a slight change in the shape of the contact patch when the wheel is at an angle is going to alter the rolling resistance in any significant way.
I also don't see much tread pattern on a typical road racing tire, so I suspect this tiny tread pattern has little effect on rolling resistance.
Here's a typical road racing tire cross section.
road racing tire cross section
Notice:
- the rubber is thickest at the top of the tire, so the volume of rubber being deflected (and thus RR) is maximized when the wheel is upright
- the "grippy" green rubber is quite thin, so any difference in RR from this rubber deflection ought to be tiny
- the tread pattern is quite tiny
Maybe I'm just dense, but I'm not seeing where this RR difference would come from.
The picture litterally shows a difference between the middle of the tire versus the the sides. You yourself pointed out the differences, yet you then concluded that the difference are tiny and ought not to make a difference. I'm baffled at your logics.
I'm sorry, but in science a difference is a difference, and whether that difference is significant or not is judged within a wider system. So, do you think a RR difference of 1-3W between two tires, when the rider is pushing 270W, mean much? I could also take your perspective and argue that 1-3W difference in RR is also
tiny (helmet straps optimization can save 5W) and thus any differences in tire construction don't mean anything. But that is not how an objective argument should work.
Let me ask you this. If tire construction optimization is not important, and only result in "tiny" differences, then why don't tire manufactures just make all tires to be the same all around, same carcase, same rubber, same thickness, same thread,.. all the way around. This would save them a lot more money then injecting "tiny" bits differences into their tire in order to try to save you that 1-3W.