Donâ€™t mean to hijack/derail the thread, or reply to anyone specifically, but I had a question regarding the article for anyone who might be able to answer.
All of the tire sizes are tested at four different PSI levels, and for each tire, a higher PSI produces lower rolling resistance and a larger tire had lower rolling resistance at a given pressure. What if you owned a wheelset such as the HED Jet+ where the max recommended PSI is 90? At that point are you limited by the wheel manufacturer recommendation? From other threads Iâ€™ve read, it doesnâ€™t seem like people who own the Jet+ run near the maximum anyways. I also realize rolling resistance isnâ€™t the end all and drag plays an important role in speed too so you wouldnâ€™t want a huge tire that balloons off the rim.
What Iâ€™m trying to ask, in a roundabout way, is what tire size would be faster for a wider wheelset such as Jet+ where there is a limit to how much you can inflate the tires? Generally most people run either a 23mm or 25mm so what does the smaller tire give you that the larger one doesnâ€™t and vice versa? Comfort? Am I trying to oversimplify a more complex subject? Thanks in advance.
Th silca blog section has some great articles on the topic. Essential reading (5 part series)
In short, on a perfect surface, higher pressures give lower rolling resistance. This is the fallacy of higher pressure= faster.
But in real life data shows that even paved roads are rougher than we think, and as pressure increases, suspension or impedance losses start to dominate after a point. That vibration you feel for too high a pressure tire is slowing you down with wasted energy.
So the trick for ultimate speed is to find the happy medium pressure for the ride conditions (lower pressure more essential as the surface becomes more rough), balancing crr and impedance/suspension losses. As a rule of thumb, comfort is faster because less energy is wasted bouncing you around. You just donâ€™t want it too low that things get sloppy, draggy.
The lighter you are, the lower that ideal pressure is. For the average road, for all but the heaviest riders on the thinnest tires, 90psi is probably as high as you need/want to go. Likley it is too high for most.
For aero gains, a rough rule of thumb is that you donâ€™t want a tire that is wider than your rim. Ideally you want narrower. So fit the narrowest tire that can still make you comfortable without rim strikes/pinch flats, and you are probably in the ballpark for the ideal for you for max performance. Closing my eyes and speaking in generalizations, most data i have seen puts 23c above wider tires on aero rims for performance, even when a rim is optimized for the wider tire. But for a big moose of a rider, 23c may be pusing it on the comfort/pressures end. It all depends.