skinnier tire vs LRR tire?

[NickelB NL]

On the bike thing. Why do speedcyclist have skinny tires and not the (safer) wider tire. More contact means more energy needed to move it. In your story i could mount a 365 tire and still use the same amont of energy.

[bikin' Ed]

As with anything there are diminishing returns. At some point weight and lack of aero will overcome LRR. However, most road racing wheels were 19mm wide and now they are 22-25mm. Cars which as a total line have to meet mpg standards, will now more likely have 55 or 60 series tires on them rather than the old standard of 75 series. Good suspension work can hide most of the tire from the headwind,leaving the aero part of the equation a moot point.

[CapriRacer]

Originally Posted by NickelB NL

On the bike thing. Why do speedcyclist have skinny tires and not the (safer) wider tire. More contact means more energy needed to move it. In your story I could mount a 365 tire and still use the same amount of energy.

I think what is going on here is that skinny tires use very high inflation pressures - and it's the inflation pressure that reduces the rolling resistance. But as was said, at the same pressure, the wider tire is better.

And using your example, if you could fit a 365 to your vehicle, it would be better for RR at the same pressure, but there would be other problems that would make that choice unsuitable. But if you reduce the pressure to solve some of those problems, then the RR goes downhill.

[HypermilerAX]

I think it's also about inflation pressure. I used to have Continental's Supersonics for races. They exist in 20 and 23 mm, but have different sidewall max's, 145 psi for the 23 mm and 175 psi for the 20 mm. At their respective maxs, I found the 20 mm to be better even at low speed. Plus the better aero and less weight. However this works only on perfect road surface. The 23 will be better on unperfect roads.

If a wider tire rolls better than a narrower tire, the surface of the contact patch being the same (same pressure, same weight), it's probably because the tire deforms less in the width than in the length. I guess that's why the tall and narrow concept will be the future according to industrials, less deformation in width and in length (larger diameter = smaller angle).