# Do the new GT3 tires hurt the slider exploit drivers?

Discussion in 'General Discussion' started by davehenrie, Feb 11, 2023.

1. ### green serpentRegistered

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Imagine if a car was parked and there were two strongmen, one pushing horizontally on the right front quater panel and the other pushing horizontally on the left rear quater panel (basically creating a "moment of force about the cars axis" to use physics speak). Assuming the contact patch stays roughly in the same spot gripping the road surface, would there not be a light amount of yaw due to tyre flex?

When cornering, obviously the car is rotating around it's own axis. So there is slip angle at the contact patch but also (what I'm saying) is there is flex in the tyre too where the rim of the tyre is pointing in a slightly different direction than the direction of the contact patch. It's this kind of squidgy rotation that isn't exactly 1:1 with the steering that people may percieve as floatyness or too much slip angle or whatever.

Again, not really sure what my point is, I guess what I'm saying is that surely the flex alone could account for some degree of rotation, then some from actual slip angle of tyre? So it LOOKS like tyre is sliding a lot but it's only sliding a bit.

2. ### LazzaRegistered

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What Sim is saying is that the front and rear tyres are pushing the same way in a corner. Unless you're in the middle of a tankslapper, maybe.

Remember the tyres are doing the turning, it's not a big hand turning the car and the tyres reacting to it (not since I was a kid with matchbox cars, anyway).

Also, I think you are overestimating the effect. Even if you had front and rear squidging 10cm in opposite directions, over a 3m wheelbase that's less than half a degree of turn.

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3. ### green serpentRegistered

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Once the tyres get the car turning, the car's mass causes a moment around it's axis. If you were to go poof and remove the planet from under the car, the car would spin around it's own axis indefinitely. So no there isn't a magical giant hand, but the "force" is still there rotating the car.

I see the chassis and rims of the car as different entities to the tyres. I.e the contact patch of the tyres around a corner are pointing in a slightly different direction than the rims. There is a slip angle between the road and contact patch, and also a slip angle between the contact patch and the rim. I thought that this was a thing, but maybe I just made it up in my own brain.

But yeah, it's probably pretty negligible anyway.

4. ### Owen PyrahRegistered

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I think the biggest feeling of vagueness you get from sliding is the spinning of the rears. Through some corners when you push the fronts you can feel the chatter as it snatches and grabs rapidly. That's mostly lateral force though. I think when the rear lets go you generally have the tyres travelling a different speed to the road.

Like on entry the back torque of the engine wants to slow the rear wheels down but the momentum of the car keeps them travelling faster. Hard on the brakes as the rear unloads it allows the rear tyres to travel slightly slower than the fronts. On exit oversteer the tyres will rotate slightly faster than the ground speed. It's where most of the grip is.

I'm really not that quick to say, but I've felt both on my bike and it's fairly vague on entry and exit. Like on entry you are just aware of what the front is doing, The back can wiggle a bit and you barely register it. On exit it's hard to tell whether you are sliding or you just have a flat rear tyre. I've had similar from the front tyre, but only where I was locking it up slightly with the brakes. Otherwise when you feel it getting somewhat close it just judders.

So like I say, I don't have that much experience but it doesn't feel massively out of the ordinary for me.

EDIT: I think the effect I'm trying to say is like how when you have a flymo lawn mower. When it is turned on it moves quite easily, when it is off it is more difficult to move. I know the tyres aren't hovering, but it sort of feel a little like they are when I've felt it on my bike.

Last edited: Feb 15, 2023
5. ### LazzaRegistered

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The way you're thinking makes sense if the car is stationary. When moving it's following an arc, and the tyres need to keep working to keep it there. All the tyres are pushing the ground away from the centre of the arc.

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6. ### mantasisgRegistered

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Not cornering, but yawing is when car rotates around its on axis. Overall neural steer mechanism is very interesting, and I don't understand it very well. But the fact is that car is still making a turn, traveling in an arc and this means that tires are still generating cornering force which means they pull the car towards center of the turn, and creates torque to produce rotation.

It is a bit weird overall how it is even possible that neutral steer is a thing at all IRL. I think not without a reason it hardly happens on tarmac, especially with high performance cars and tires. And is a lot more seen on loose surfaces like snow and gravel, even more so with AWD cars. Thats probably because the vector produced by driving power allows car to turn while otherwise it would just slip off the curve in straight line. I guess to maintain higher amount of neutral steer helps a lot if traction circle is friendly for more throttle application, this way you can vector slightly overslipping car to keep it in a curve, without totally loosing the rear tires and spinning off wildly. Well you can but how much - realistically, or too much ?

Honestly most neutral steer I have seen were for very very short moments. Maybe this is also why it is rarely talked about, as opposing to very noticeable oversteer and understeer. For a driver that split second when neutral steer happens is very meaningful because it allows to win rotation, but it is also very risky because it is unclear if car will understeer or oversteer from there at any moment. But if such slide lasts predictably for "many moments" then driving fast becomes more predictable.

Bit off topic: I think it would be very interesting to see animations showing how instantaneous centers of whole car rotation changes real time as car is being pushed over the limit and switch to understeer>neutral steer>oversteer and other possible combinations.

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7. ### green serpentRegistered

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I think we're getting caught up with semantics and god know how it relates to the original point, BUT I will have to respectfully disagree with you! Disclaimer: I could be wrong I will do some research when I can!!!

I think when you are thinking of a car rotating around it's axis, you are thinking of it as yawing out, i.e changing it's slip angle to be in an oversteer state relative to the curve. But even if a car isn't oversteering, if it's cornering, it's STILL rotating around it's own axis (be it the rear axle or it's centre of mass or wherever). It literally has to rotate around it's own axis or it wouldn't be turning.

Think of it this way... The sun is the fulcrum of the corner, ie it is in the centre of the large arc that the earth (car) is orbiting around (please bare with me!)

In this anaology, the earth is rotating around the sun, but the earth itself is visibly spinning on it's own axis - so the earth is "oversteering", it's spinning out, and it's all very obvious and self evident from all who observe.

So, question for you (and here we get to my point). The moon orbits the earth (obviously). But, does the moon spin on it's axis? To an observer on earth, it sure doesn't look like it's spinning around it's axis. You look up at it every night or day for a month and see the same craters etc. Like a car going around a corner dosn't look like it's spinning. But the moon does spin, once for every time it goes around the earth.

So a car dosn't look like it's spinning on it's own axis as it's cornering, because it's rate of spin kind of matches the curve and camouflages it. But it is spinning (not necessarily yawing though).

Edit: so just to clarify, if a car successfully navigates a 180 degree turn, the car has in fact rotated around it's axis 180 degrees. If a car makes a full circle, it has rotated around it's axis once.

Last edited: Feb 15, 2023
8. ### LazzaRegistered

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Shoot, even I'm out at this point. Language is a wonderful thing - or so they say.

9. ### mantasisgRegistered

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No problem. I am always eager on researching too, just did some research about the moon because I did not know few things.

Don't forget point of reference is a thing in physics. Which in our case should be in the car.

P.S. if earth was oversteering or understeering we would be in big big biiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiig trouble lol

10. ### ComanteRegistered

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I don't think you can understand vehicle dynamics if the system reference is the car itself. It is much easier to figure if you put your virtual self in the centre of the turn radius. Here you can see all the primary and secondary movement that all car parts have to accomodate the forces generated.

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11. ### ComanteRegistered

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But in short, people that doesn't like sluggish feeling of GT cars, should turn their attention to open wheelers those are the real racing cars snappy and zipping fast.

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12. ### mantasisgRegistered

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Center of turn is probably valid reference point too depending what you are looking for. Not the center of the universe or Gods hand though. Ok I am out too at this point.

13. ### green serpentRegistered

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Perhaps my analogy was a bit too abstract! Guilty as charged. In as plain of english as I can: A car has to rotate about it's own axis to turn. At the begining of the turn the tyres have to overcome the polar moment of the car and accelerate it into a steady rotating state. This is why cars tend to understeer on corner entry. At the exit of the turn the tyres have to do the opposite - slow down and stop the angular velocity (rotating) of the car. This is why often oversteer on exit is really common. I was simply trying to explain that even though a car might not LOOK like it's spinning, it does in fact have angular velocity. The tyres have to deal with this angular velocity, AS WELL AS the centripetal cornering force. I hope that makes sense.

But yeah, when it comes down to it, heavy car = bad. Drive a lighter car if you want less floatyness.

14. ### doddyncoRegistered

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This 'floatyness' you guys are experiencing may be down to something completely unrelated - a bug introduced in the RC.

Check your controller json. If the 'wheel rate' setting is less that 1, your inputs are being filtered/delayed. Causing occilations and a general lack of attachment to the sim.

It will be fixed for the release I think.

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15. ### davehenrieRegistered

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which line exactly, a lot of rates for various items in there...

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