Originally Posted by
cyccommute
And a wider tire gives an even larger tire patch.
No,
Much of this discussion is subjective. This point is not. The size of the tire patch is a function of tire pressure, NOT tire volume. For a given load, two tires of different sizes at the same pressure with have the same area of contact patch.
None of the advantages I mentioned (comfort, traction, control on rough surface) will be gained if you run a larger tire but don't drop the pressure. Other than gaining some float in deeper loose stuff, you will gain almost nothing, Especially on the road. You may disagree, but you are in a small minority.
Originally Posted by
cyccommute
There is a difference in rolling resistance but I really question the claim that it’s half. Comparing a
Vittoria Voyager (37mm) to a
Vittoria Zaffiro (25mm) on Rolling Resistance, cutting the pressure in half doesn’t result in a lower rolling resistance for the wider tire. The Zaffiro has a 16 W rolling resistance at 100psi. The Voyager has a rolling resistance of 21W at 45 psi. The rolling resistance of the Voyager doesn’t equal the Zaffiro’s until 75 psi. In other words, a “literally” half the tire pressure, a wider tire from the same manufacturer wouldn’t roll faster. It would roll the same at 20% reduction in pressure and roll slightly faster (14W vs 16W) as the narrower tire at 90% of the pressure. That also doesn’t take into account the change in aerodynamic drag nor the difference in weight (150g of rotating weight)
.
I did not say ALL tires would give you the same rolling resistance at 50% pressure I was speaking about the ones I use.
But regarding that comparison; that is not a good comparison as these are completely different tires. They are NOT different sized version of the same tire. The larger tire has an extra puncture resistance layer (which will add RR). Also, it is not a slick... it has some tread.. Remember, I specified PERFORMANCE tire, and NOT a touring tire. And then there is the issue of the reliability of using roller drum testing to predict real world results. This is not universally accepted. I take them with a grain of salt as they deform the tire differently then a flat surface does.
Anyway, this topic (tire pressure and larger tires) has been discussed and reported on exhaustively. I'm not going to rehash it here. When it comes to the issue of pressure and rolling resistance in larger tires, my take on this is the one gaining more acceptance as more people try high performance high volume road tires (which were few and far between up until a few years ago).