New Tyre Physics (work in progress)

[Calvinaquino]

I never (and maybe wont ever) drove in iRacing, but i just drove a few laps in GPL and i noticed the tires loose traction in a more smooth way. So from what i read, people say that GPL was one of the most realistic sims out there (some say it still is), and i can't say anything about Iracing, but what i'm understanding is that this tire physics rework will make the load/traction curve of the tire more smooth?

I hope i made any sense, its 4a.m. here and i'm with a small headache... gotta go to bed.

PS: when i think about all the equations and variables involved in it... I don't know how Scawen's head hasn't already exploded by the amount of stuff he has to research/write/look at. =D

[LILSTIG]

Ouh gosh ouh gosh! I cant wait for this update!!!

[Takumi_lfs]

Originally Posted by LILSTIG

Ouh gosh ouh gosh! I cant wait for this update!!!

You'll have to... Don't worry, it wont take long anymore. in your dreams

[AndroidXP]

Originally Posted by Calvinaquino

I never (and maybe wont ever) drove in iRacing, but i just drove a few laps in GPL and i noticed the tires loose traction in a more smooth way. So from what i read, people say that GPL was one of the most realistic sims out there (some say it still is), and i can't say anything about Iracing, but what i'm understanding is that this tire physics rework will make the load/traction curve of the tire more smooth?

No, read again

What codehound said was that LFS is between GPL (worse) and iRacing (best) in terms of feeling what the tyres do. I cannot say how accurate GPL's tyre model is in comparison to modern ones. You have to keep in mind, though, that GPL models a completely different type of car with the completely different bias-ply tyres (which are very stiff and have almost no sidewall flex), so I don't think a 1 on 1 comparison is fair in that regard. That said, I think people have a bit of a rose-tinted-glasses issue going on when saying that GPL is still the most realistic sim out there. Maybe the one they're most accustomed to, but realistic? Well, who knows, different car and all that.

In regard to LFS, what most people say they feel is wrong is the way tyres lose/regain grip - it seems to happen too smooth, too gradual. So if anything is going to change then I'd say it's rather going in the opposite direction of GPL-like smoothness. However, we don't really know anything about the new tyre model, other than what Scawen said and that the beta testers approve of the changes.

One thing I'm fairly certain of is that the new tyre model will have more load sensitive tyres, since that is from my understanding of tyres the only thing that would fix the issue Scawen described (too much grip on outer wheel, simply reducing grip won't fix it but would only shift at what speeds the problem occurs). By increasing the load sensitivity, the outer, loaded tyre would work less well than now, resulting in a more equal spread of how much the loaded tyres provide grip compared to the unloaded ones.

This should have a quite profound impact on how the cars feel and more importantly how they have to be set up to drive well. First, anti-roll bars will have more of an effect and the effect won't be the opposite from what you expect. The stiffer end of the car would then have considerably less grip, since the loaded tyre (which in a corner also bears some weight of the soft end of the car) wouldn't be as grippy as now. Second, the way differentials work would be vastly different.
Right now, having low-medium locking diffs is not feasible for the most part. Such a diff works rather poorly in corners, since most grip is on the outer tyre whereas the inner one barely contributes and easily starts spinning, taking away power from the outer wheel. For the same reason, high locking or locked diffs don't cause nearly as much turning problems as they should. Again, the inner tyre barely contributes, meaning the tyre that should normally fight against turning the car just sits there doing nothing. The currently fastest setups exploit both these deficiencies to their full potential. On one hand, they use locked diffs (or clutch pack diffs with 800Nm preload, claiming it feels better/not being a locked diff exploiter, ironically without realising that at such preloads the diff is for all intents and purposes locked), granting them full power even when the inner wheel is in the air. On the other hand, they give full ARB strength to the end of the car with the locked diff, causing all the load to go to the outer wheel (sometimes even lifting the inner), reducing the negative impact on turning to zero. This is mostly done on FWD cars, but really all cars "suffer" from high locking diffs being too viable. Overall it would be more important to make the inner tyre do some work, as the outer tyre alone would be much less efficient than both tyres working together.

[JasonJ]

My cat's name is Mittens.



Thanks for the wisdom. Now my head imploded

[Breizh]

Thanks for that post Android.

[Napalm Candy]

To me the feeling in iRacing it is not so good. If you try the pontiac solstice (low powered RWD) and go to the centripetal track, try to do drift arround, is IMPOSIBLE to do 1 lap with out a spin or go out. In RL is more easly, so what i feel in iRacing is too low grip when slide/drift, and uncontrolable, that's not realistic

But I'm agree with you in the side load of LFS tyres, is flexing too much

[wheel4hummer]

I definitely agree about traction loss being too gradual in LFS with respect to what I have experienced in real life. Not too long ago I crashed my car going a bit too fast into a corner. My shock absorbers probably need to be replaced, who knows if that contributed. Anyway, a small bump in a corner caused me to lose traction. But I didn't understeer, the back end of my car just decided to come out. I stupidly slammed the brakes, and then what I ended up doing is over-correcting and spinning the other direction. Then the front end of my car hit the guardrail and the back end of my car swung around and hit the guardrail. It doesn't seem possible to get LFS to act this way in it's current state, though there's no corners like the one I crashed on in LFS.

[george_tsiros]

all i want to say is this:

the behaviour of the contact between tyre and ground and the behaviour of the tyre itself is ridiculously complex, simply impossible to model accurately, even if one started having a perfect model of the asphalt and a perfect model of a tyre, modelling the dynamics of the contact between these two is nearly unfeasible, let alone done in realtime. many different materials in different conditions etcetcetc.

lfs is nothing short of a miracle. can't talk about any other sim.

[Hallen]

Originally Posted by AndroidXP

No, read again

What codehound said was that LFS is between GPL (worse) and iRacing (best) in terms of feeling what the tyres do. I cannot say how accurate GPL's tyre model is in comparison to modern ones. You have to keep in mind, though, that GPL models a completely different type of car with the completely different bias-ply tyres (which are very stiff and have almost no sidewall flex), so I don't think a 1 on 1 comparison is fair in that regard. That said, I think people have a bit of a rose-tinted-glasses issue going on when saying that GPL is still the most realistic sim out there. Maybe the one they're most accustomed to, but realistic? Well, who knows, different car and all that.

In regard to LFS, what most people say they feel is wrong is the way tyres lose/regain grip - it seems to happen too smooth, too gradual. So if anything is going to change then I'd say it's rather going in the opposite direction of GPL-like smoothness. However, we don't really know anything about the new tyre model, other than what Scawen said and that the beta testers approve of the changes.

One thing I'm fairly certain of is that the new tyre model will have more load sensitive tyres, since that is from my understanding of tyres the only thing that would fix the issue Scawen described (too much grip on outer wheel, simply reducing grip won't fix it but would only shift at what speeds the problem occurs). By increasing the load sensitivity, the outer, loaded tyre would work less well than now, resulting in a more equal spread of how much the loaded tyres provide grip compared to the unloaded ones.

This should have a quite profound impact on how the cars feel and more importantly how they have to be set up to drive well. First, anti-roll bars will have more of an effect and the effect won't be the opposite from what you expect. The stiffer end of the car would then have considerably less grip, since the loaded tyre (which in a corner also bears some weight of the soft end of the car) wouldn't be as grippy as now. Second, the way differentials work would be vastly different.
Right now, having low-medium locking diffs is not feasible for the most part. Such a diff works rather poorly in corners, since most grip is on the outer tyre whereas the inner one barely contributes and easily starts spinning, taking away power from the outer wheel. For the same reason, high locking or locked diffs don't cause nearly as much turning problems as they should. Again, the inner tyre barely contributes, meaning the tyre that should normally fight against turning the car just sits there doing nothing. The currently fastest setups exploit both these deficiencies to their full potential. On one hand, they use locked diffs (or clutch pack diffs with 800Nm preload, claiming it feels better/not being a locked diff exploiter, ironically without realising that at such preloads the diff is for all intents and purposes locked), granting them full power even when the inner wheel is in the air. On the other hand, they give full ARB strength to the end of the car with the locked diff, causing all the load to go to the outer wheel (sometimes even lifting the inner), reducing the negative impact on turning to zero. This is mostly done on FWD cars, but really all cars "suffer" from high locking diffs being too viable. Overall it would be more important to make the inner tyre do some work, as the outer tyre alone would be much less efficient than both tyres working together.

I'll pretty much have to agree with all of that. Isn't it amazing how all of that comes together with that small statement from Scawen? With that explanation, we can now infer a bunch of things. Ah, I see, the load model for the tire grip is off and therefore...

[wien]

Originally Posted by AndroidXP

...

See, now you've just gone ahead and raised my excitement level several notches. That just makes sense and it'll be interesting to see if it pans out that way.

[Pu1se]

I am eagerly awaiting this update =)

[Danny LFS]

Finally some improvements on those tyre physics. I was starting to wonder when the FBM would ACTUALLY handle like it should - good, but it handles TOO good on the current version.

[kamkorPL]

Originally Posted by wheel4hummer

I definitely agree about traction loss being too gradual in LFS with respect to what I have experienced in real life. Not too long ago I crashed my car going a bit too fast into a corner. My shock absorbers probably need to be replaced, who knows if that contributed. Anyway, a small bump in a corner caused me to lose traction. But I didn't understeer, the back end of my car just decided to come out. I stupidly slammed the brakes, and then what I ended up doing is over-correcting and spinning the other direction. Then the front end of my car hit the guardrail and the back end of my car swung around and hit the guardrail. It doesn't seem possible to get LFS to act this way in it's current state, though there's no corners like the one I crashed on in LFS.

I don't really think it's too gradual from my experience. It's pretty damn close. I guess it also depends a lot on car setup. My e30 325i is very predictable. But for example stock fiat seicento is much less predictable.

There are some other aspects than tires that play a role to snapiness in real life too I think. Like open diff, or old soft bushings that make things feel more "laggy".

Most people have this weird belief that it must be snappy to be realistic.

I found the biggest transition from drifting in lfs to real life, is getting used to all the gforces and learning to use them in your advantage. Also changing road conditions are what makes real life much different to me. Also I never experienced snap back to other direction in real life (ofcourse drift transitions don't count here). Could be that rwd cars are just much more safer and more predictable. So ditch your fwd, and get an rwd!

And yeah dampers could play a role here. I drove a car with shit dampers at front, and during higher speed cornerning front felt like it was "jumping", I don't want to think how it would act sideways, but probably wouldn't be very easy to control. Shit dampers + bump + sideways + lack of experience + wrong reaction + overcorrecting =

Anyway, I hope you weren't hurt in this crash and good luck fixing your car.

[Calvinaquino]

Great post android, now i unserstand better what is happening and what to expect.
This is going to be a helluva patch...

[Shotglass]

Originally Posted by kamkorPL

I don't really think it's too gradual from my experience.

one thing to keep in mind is that in lfs drift setups generally use overinflated tyres while racing setups use way underinflated ones
the underinflated one have much less cornering stiffness and thus begin to slide much more gradually than both the overinflated and the real life ones

[legoflamb]

The beta-testers making a trustworthy opinion on the physics/handling of the Sirocco in LFS begs the question: What experiences have the beta-testers had with the Sirocco in RL, and what kind of "credentials" do they have with performance driving/racing?

Are there VW test-drivers beta-testing?

Are there experienced racing-drivers beta-testing?

Who are these beta-testers?

Of course answering the question of 'who' would not be a good idea, because of the harassment they might/will get from eager LFS players.

[aoun]

Originally Posted by legoflamb

The beta-testers making a trustworthy opinion on the physics/handling of the Sirocco in LFS begs the question: What experiences have the beta-testers had with the Sirocco in RL, and what kind of "credentials" do they have with performance driving/racing?

Are there VW test-drivers beta-testing?

Are there experienced racing-drivers beta-testing?

Who are these beta-testers?

Of course answering the question of 'who' would not be a good idea, because of the harassment they might/will get from eager LFS players.

Check the credits when you exit LFS. theres a list of the beta testers there.

[adamkob32]

Originally Posted by Napalm Candy

To me the feeling in iRacing it is not so good. If you try the pontiac solstice (low powered RWD) and go to the centripetal track, try to do drift arround, is IMPOSIBLE to do 1 lap with out a spin or go out. In RL is more easly, so what i feel in iRacing is too low grip when slide/drift, and uncontrolable, that's not realistic

But I'm agree with you in the side load of LFS tyres, is flexing too much

Try drifting in real life on a set of Hoosier R6's like the Solstice has in iRacing, it doesn't work. Race tires snap and are hard to catch in a slide. It's the same as trying to drift one of the GTR's in LFS, very very difficult.

I can't wait to try out the new model. I haven't run LFS in a long while. This is a very anticipated update for me!

--Adam

[Calvinaquino]

Originally Posted by aoun

Check the credits when you exit LFS. theres a list of the beta testers there.

Unless there is also written what they do, i think he meant, how much the beta-testers know to be able to judge the new physics. I bet Scawen didn't picked up any person who volunteered (is it right?) to be. I think he picked people with a background (physics related, racing related).

[Matrixi]

Originally Posted by adamkob32

Try drifting in real life on a set of Hoosier R6's like the Solstice has in iRacing, it doesn't work. Race tires snap and are hard to catch in a slide. It's the same as trying to drift one of the GTR's in LFS, very very difficult.

What the man said. The Solstice isn't running on street/sports tires like many people seem to think. That doesn't mean that it would be impossible to drift though, I recorded this short clip to prove that almost a year ago.

http://www.youtube.com/watch?v=YGrqebP-xGU

[Falcon77]

Originally Posted by AndroidXP

One thing I'm fairly certain of is that the new tyre model will have more load sensitive tyres, since that is from my understanding of tyres the only thing that would fix the issue Scawen described (too much grip on outer wheel, simply reducing grip won't fix it but would only shift at what speeds the problem occurs). By increasing the load sensitivity, the outer, loaded tyre would work less well than now, resulting in a more equal spread of how much the loaded tyres provide grip compared to the unloaded ones.

Nice post there

The interesting (and confusing) thing for me is that more load sensitivity generally means more understeer (under braking) and generally snappier behavior. I've just recently discovered the huge influence of the load sensitivity curve on my own tire model (far from LFS standards, but still something worth playing with ).
What's also interesting is that if the issue is "simply" load sensitivity, how come the whole model is being changed? I would have two ideas:
- The load sensitivity is derived internally from some the model itself, and Scawen wouldn't see it fit to change just this part of the model (plugging in a "custom" curve for the load. sens.)
- Since he started working on the model, he thought of other things to improve and the original issue led to an (unrelated) whole rewrite of the model

These are the ideas I can come up with from the information given, but I have the feeling that the information we have does not completely describe the situation. I don't think a 2 sentence brief from Scawen says enough about the whole model

[Dajmin]

Presumably he just didn't want to go into the detailed changes because most of us wouldn't understand what they mean. And it's possible that what's in Scawen's latest test patch might change again before release, so things discussed might never go live.

I'm looking forward to the changes, because more realistic settings are always going to be good. So maybe running stupidly low pressures will cause you problems rather than just giving you unrealistic levels of grip.

Pretty sure we'll find out one way or the other once it's ready. Then we can start arguing about how "the changes have broken the game" and that "nobody can drive any more" and that "lap times have increased by seconds" and that "the old system was better" and all the crap that comes with every incompatible patch

[tristancliffe]

Originally Posted by kamkorPL

I don't really think it's too gradual from my experience...

Most people have this weird belief that it must be snappy to be realistic.

The loss of grip in LFS and in real life is very gradual, but in real life tyres do tend to regain grip quite suddenly, which is this snappy thing you refer to, and LFS is a little to relaxed on that front. I've found that in LFS once you start sliding it's actually quite difficult to end that slide even if you've got it 99.9999% corrected. In real life you correct it about 90% and the 'snap' does the rest...

[wheel4hummer]

Originally Posted by tristancliffe

In real life you correct it about 90% and the 'snap' does the rest...

Unless you're counter-steering too much while it snaps, or don't turn the wheel straight fast enough when it gets traction, then you just start spinning in the opposite direction, right?

Like the Evo at 8sec in this video:
http://video.google.com/videoplay?do...1050205599754#

Also, why is it so much more difficult to correct oversteer at all in an open-wheeled car in LFS then in road cars? Is it like that in real life too?

[Falcon77]

Originally Posted by tristancliffe

In real life you correct it about 90% and the 'snap' does the rest...

..And that snap is also quite visible in a lot of videos/incars. Unfortunately AFAIK it's extremely hard to reproduce in a sim, in fact I cannot name any that does it well..

[AndroidXP]

Originally Posted by wheel4hummer

Like the Evo at 8sec in this video:
http://video.google.com/videoplay?do...1050205599754#

Bad example. First, the behaviour on dirt is very different than on tarmac. Second, that Evo actually hit something on the side of the road with its back, which is what made it spin around.

[bandaid]

There's a porsche a bit further in that gives a better example but it slews off road.

[Falcon77]

Originally Posted by AndroidXP

Bad example. First, the behaviour on dirt is very different than on tarmac. Second, that Evo actually hit something on the side of the road with its back, which is what made it spin around.

Actually the fishtailing Megane right after it may be a better example

[kamkorPL]

Originally Posted by tristancliffe

The loss of grip in LFS and in real life is very gradual, but in real life tyres do tend to regain grip quite suddenly, which is this snappy thing you refer to, and LFS is a little to relaxed on that front. I've found that in LFS once you start sliding it's actually quite difficult to end that slide even if you've got it 99.9999% corrected. In real life you correct it about 90% and the 'snap' does the rest...

You've got a point there Tristan. Although I think it depends on steering feedback (forcefeedback in lfs) too. Car settings matter too. When I started I was indeed often using that snap to finnish a drift at some point. It also helped me quickly regain grip to avoid a spinning car. But recently I noticed it's better to gradually steer to center on power out. It looks nicer too. It's just a bit uncomfortable with steering that e30 has - 1440 degrees from lock to lock.

But still I am even afraid to say its snappy, because people really take that word seriously. It's snappy in an easy way to control, and it is only making things easier not harder. Let's hope new lfs tire physics adress this issue and several others. And the funniest thing is, drifting in lfs is a bit too hard now, some stability is missing in tires. I really can't wait for this new patch.

p.s.: What I wonder is how slick tires really act on a street alike car. And how much difference in for example snapyness there can be beetwen one slick and another. And if slick is really as snappy as people say. I'd like to hear input from people who tested them in real life and not opinions based on slip angle diagrams though. I would be for example very interested to hear Tristan feedback on slick tires, even if only from open wheeler experience. Tristan please? And maybe opinion from someone who tested slick tires on normal (non formula) car as well.

edit:

using snap back example: http://www.youtube.com/watch?v=oTJZK1szuLk 27th second. Simply easier to end drift in that place and requires less effort. But looks not very good.