Tire sidewall flexing

[Parnelli Bone]

Sorry if this topic pre-exists...I searched, bla bla bla..

This is something I noticed a while back as I watched a replay of the Shelby Cobra: tire-flexing. As this car cornered and brakes heavily, PD actually modeled the car's tires so that they flex and compress as the contact patch increases. Below is a pic of my '54 Corvette (again) to give an example.



Click to enlarge.

Good job, PD! + Rep! Tires from yesteryear often had lower psi (pounds per square inch) requirements when you inflated them with air than they do nowadays, which is perhaps what this is all about.

 

[daan]

That looks like its just a tyre that doesn't know exactly where the graphic representation of the road is compared to the real, actual, computer generated road.

 

[Parnelli Bone]

That looks like its just a tyre that doesn't know exactly where the graphic representation of the road is compared to the real, actual, computer generated road.

It's not. Take a drive in a Cobra or C1 Vette, I really believed PD modeled them to include low-inflation tires because they are the only cars in the game I've found so far that feature such behavior.

I know back in those days, tires weren't supposed to be inflated as highly as they are now. The Corvair, for instance, needed 12 psi up front and 19 in the rear, according to a recent car book I read. Can't find any info on what a C1 Corvette required, but it's probably not anywhere near the average most cars today need, which is anywhere from 26 to 35 psi, at least in the states.

I'll get some more pics up as time goes on...

 

[VTiRoj]

I have to agree with daan, it looks like the tyre is cutting into the road. Heck, the lighter shaded part of the tyre is even cutting in.

I believe the flex is there though, just GT4 does a poor job of showing it.

 

[Parnelli Bone]

Wow, nobody agrees so far? Has anybody noticed what I'm talking about?

Perhaps sidewall flexing is a bad term, since the white strip of the tire indeed is not behaving as the tire is at its contact patch. I still think PD modeled this effect intentionally, though.

 

[SolidSnake15]

I have to go with what Daan and everyone else is saying, it looks like the tire is just cutting into the road. Plz don't kill me!!!

 

[Parnelli Bone]

I'm not gonna kill anyone! I have to disagree with everyone, tho.

But answer my question: has anyone noticed what I'm talking about? Cobra and C1 Corvette? Anyone? Bueller?

 

[MadMax]

I'm not gonna kill anyone! I have to disagree with everyone, tho.

But answer my question: has anyone noticed what i'm talking about? Cobra and C1 Corvette? Anyone? Bueller?

I will have to say that my opinion is neutral until I have tested this car
in jumps -> hit the ground and see if there actually is supression in the tires wiable.
I belive this is the best way to overload the tires intentionally.
and some ballast may give even better results

 

[mymaster]

Not car specific but I know what your talking about, sorry the pics aren't lighter so to see better.

 

[Parnelli Bone]

Naw...ballast doesn't make a difference. daan is right about that part...the tire doesn't actually flex. The effect is there to make it seem as if it does, though. It only happens to some cars, the C1 and the Cobra are the 2 I can think of off the top of my head.

So far, there seem to be three groups of thinking here

1). The road has essentially two surfaces. One is visual, the second lies centimeters below the surface we can see...hence, the car's tire is cutting thru the visual surface and into the actual one.

Problem with this theory is...why aren't ALL cars prone to having their tires dip into the road?

2). daan is essentially saying the Shelby's and C1's tires can't put their contact patch on the true visual surface of the road. Essentially, he's saying this is a glitch specific only to the Shelby Cobra, C1 Corvette, and perhaps a handful of others.

3). My thinking, which is PD somehow intentionally programmed this visual distortion to happen, the way they programmed the Chrysler Crossfire to have a small wing that rises and falls with speed. The way they programmed only a handful of cars that have automatic transmissions (or auto/manual ones) in real life to shift without any lag between gear shifts, like the Jaguar S type R and a handful of Mercedes.

So it could go either way. Could be a glitch, or it could be intentional.

 

[GrahamP]

I reckon it could be unintentionally programmed that way, especially as the lighter part of the tyre is digging into the road. I've seen the same effect on aircraft tyres in flight simulators caused by incorrect data for the vertical position of the aircraft model making it lower than it should be.

 

[Parnelli Bone]

Okay, hope I can get this to work...



CLICK TO ENLARGE PICTURE

Okay, check out this picture of this 1958 Ford Edsel. Look at its tire contact patch, in comparison to the sidewall. This is what I was trying to describe earlier, and what I believe PD is trying to simulate: an increased contact patch caused by tires that require lower psi (pounds per square inch) than modern tires often do. Radials were not being used on many of these older cars, too.

 

[EJRocky]

That looks like its just a tyre that doesn't know exactly where the graphic representation of the road is compared to the real, actual, computer generated road.

This man is bang on the money.

But, it could well be that PD did it intentionally - letting the tire model go slightly underground when it's under pressure. It would be very hard, if not impossible, to physically make the tire model bend and contort. In your photo of the Corvette wheel, it sure does look like it's flexing and under pressure - because the tire model went slightly underground. I think that may have been intentional.

 

[Wolfe]

It's better for the tires to occasionally penetrate the ground than it is for all of the cars to look like they're floating inches above the pavement. I imagine that's why PD set the collision box for the track surface slightly below the visible surface.