Tire Width Differences in Performance

[dontlifttoshift]

Donny, is this due to the outside diameter?

No, but that is a factor in the shape of the patch. Taller tire, longer patch than a shorter tire of the same width.

Doesn't that ignore sidewall stiffness?

Yep.

It'll limit how long the contact patch gets regardless of width. Even an uninflated tire has lots of resistance to being squashed and lengthening the contact patch.

Yep. Over simplified, I said :wink:

So a car weighs XXXX lbs, it will compress a tire by that much so on a narrow tire it will compress more front to rear, and on a wide tire it will compress more side to side? If this is correct then in a straight line, not under load, both tires would have the same grip?

Grip is sort of a function of load so I'm not sure I can accurately answer that question.

Not sure I agree with this, but I am quite willing to hear the explanation. Pressure may be the key. My C10 with 335's needs 21-to-24 lbs in front to get the temps even all the way across the tire. The rolling contact patch is appx 1.75" x 9.75", or 17.05 sq,in. With a 275 tire, it needs 26-to-28 lbs to get the temps even, at that pressure the rolling contact patch is appx 1.65" x 8.4", or 14.12 sq.in. (note that the larger tire is only 17% larger on the contact patch at these pressures). I would agree (haven't tried it, so this is a guess) that if we aired the 315's to 27 lbs, the contact patch would get smaller, maybe equal to that of the 275 tire at the same pressure, but this set up would run hot in the center, and not maximize the tires ability. Likewise (I guess) if we dropped pressure on the 275 tire to 22 lbs, the contact patch would grow - here's where I get lost - but, due to the cupping of the tire under load, I'm not sure the center of the contact patch would actually touch the pavement, as this would show the center temps much cooler than the outsides. - Donny?

I don't have to explain it, you just did. Same pressure, same load, same size patch. But the wider tire can operate at a lower pressure. Less pounds per square inch means we need more square inches to support the same load - boom, more contact patch. As far as the tire cupping under load and giving up grip through the center, that could only be determined by measuring tire temps in real time. It's probably not as drastic as either one of us would think. It would probably be extra sloppy on turn in and likely would roll over onto the sidewalls alot.

Please note, I have not said which one is better but I don't know anyone that has put wider tires on and gone slower. At this point, I'm not sure the gains are as large as I would like to believe. I also don't know anyone that has done any A-B-A testing on a PT car. I would love to see a handful of cars tested that could run 275/275 315/315 and 275/315 all on the same tire brand. Perfect cars for this dream test would be Maiers mustang, NoLimits truck, the ridetech 33, and the DSE 2nd gen but I would like to see all of those cars with 400hp at the wheels because all of those cars will melt 275s on the rear in short order. Those cars are all well sorted. Bring in Mary, Junior, and Strano to drive them. Also test the 275s on 9.5" and 11" wheels.