AudiJon

Gross oversimplifications are not the best way to look at things, IMHO. It's something that my roommate does all the time and it bugs me.

Also, dragsters don't use skinny (driven) tires last time I checked, which was at a pro event this weekend (don't ask, we we're bored...).

Mark Dalen

This is not even close to a correct model for tires. There are major mechanical/structural aspects to a tire. On top of that, the pressure not only supports the wieght directly, but also stiffens the sidewall, adding to the structural aspects of the tire.

Pressure has a very small impact on contact patch. If you do not believe me, then go do a test with some paint and paper and varied tire pressures.

John/TSR

...air pressure supports the car, which is a gross simplification of the mechanics of a pneumatic tire.

Reality ? The tire SIDEWALLS suppport the weight of the car. All the air pressure does is make those sidewalls conform to their design shape, and give the structure significant rigidity.

Ever wonder why you can set tire pressures with your car on jackstands, and it doesn't change when you drop the car on the ground ? Why is that ? Because it's the sidewalls that support the weight.

Pat-SoCal

And not just because one runs with 10psi and the other with 40. You can literally fold a drag slick in half... even the M&H drag radials (DOT legal) on my mustang, which are bias ply's can be collapsed in on themselves. Those tires are designed to lose their structural rigidity so that they have a larger contact patch to the road surface. Matter of fact they work so good you have to screw the tire to the wheel so the wheel doesn't spin inside the tire. You don't usually pay attention to this in road racing outside of NASCAR in which case they only mark the alignment of the tire to the wheel; also a bias ply.

Tread width will affect the size of the contact patch. In road racing, the car will benefit by having a larger contact patch in all aspects except for acceleration due to increased mechanical drag on the pavement. Small price to pay IMO for another [hypothetical] 5mph of corner exit and 50ft. shaved off a braking zone.

The relationship between section width and tread width is worth paying attention to because combined with your wheel size you can start to factor in how much deflection the tire will see under load and therefore adjust the chassis accordingly.

AudiJon

One night while cruising around town in the S4, I had one tire that was underinflated (or leaking air for some reason) and had a blowout going down the highway. It was the left rear and when I pulled over and got out to inspect the tire I was shocked to see that the entire tread had blown out and sperated completely from the sidewalls. The only thing left on the rim were the two sidewalls and they were supporting the car just fine.

Strange sight, but I learned two things that night, one of them being to check my tire pressures more often!

ast78

noob ? why is a wider tire worse under braking?

s4wood

And I thought it was the lycra..boy was I wrong.

Pat-SoCal

so your nutz don't swang to and frow!

John/TSR

W/metal detectors in every airport, I'd guess you've given up on that 'under-wire' thing...

Mark Dalen

When you check the tire pressure with the car on the jacks, there is 0 pressure. I use Helium in my tires and get -12 psi on the jacks. That way, when the car is on the ground, it only weighs 750 lbs. Now you see how to properly corner balance a car.


Sheesh, next thing you are going to admit you don't even know how to operate tear-offs.