AC tire model explained

Hi,

I wonder how advanced the AC tire model is compared to other sims.

-I don't know much technical details, but I know that iRacing has a pretty advanced one. You can feel it best by driving the RUF. It's like no other in my opinion.

-I know that the physics guy from LFS wanted to implement something similar that iRacing has, but obviously failed on the task, as LFS is pretty much dead now.

Thanks

 

yes

 

AC and iR are fairly similar in features. The only major difference I know of is that AC includes dirt buildup when you go offtrack and iR doesn't. They both have tire temperature/wear affecting grip, and a reasonable model of rolling friction. I think they handle low-speed (as in under 3km/h) differently but I don't like either one so.

Most differences you feel between them are probably going to be down to specific tuning parameters set per car. And some might say that AC does better at large slip angles but that's not super relevant to racing.

 

pretty sure rf2 is the most advanced out of the bunch, at least thats how it feels. I love AC though anyway. Each sim has things to love about it.

 

Have the devs also said they had a more advanced tire model in house? or was that the .4 tire update model we got way back?

 

I think you are dead wrong when you assume, that AC or even rFactor, has the same kind of tire model that iRacing has.

Watch this video from 16:15 where David Kaemmer is talking about the new tire model (version 5) of iRracing.



This guy has been making the best sims around for 20 years, and yet he has no problem to confess, that developing this stuff was extremely challenging, and long process. We don't really know if any development of LFS is still going on, but it's very likely that Scawen (LFS physics guy) realized that he isn't gonna make it without reading some advanced physics books which takes x years to digest and realize in code.

I think AC is doing a pretty good job on physics, but you just don't get that sensation of driving the RUF on the new tire model of iRacing.
It's like another level.

 

I raced iRacing for about four years: 08-12. Dave was already famous for his 'brilliant' physics, because of GPl, Nascar 03 etc. But still iRacing had ahorrible tire model. The introduction of the NTM even made things worse. IRacing now is on NTM 6? It shows they really messed up a lot frankly.

I do believe IR is moving in the right direction now though. But I have the impression they are converging more to AC's tire model. Mind you, I haven't tried it. Just heard others talk about it.

Dave k isn't god. And complexity does not equal good. AC's core mathematical model is quite well developped. Featurewise, like flatspotting etc there is room for improvement.

 

I think AC's low speed physics are still a work in progress, I'm sure I read somewhere on here there will be improvements to come.

 

Disagree entirely. The iRacing tyre model is junk. I literally can't go back to it anymore, its so stupidly bad. At the limit, it does the most bizzare things, I find it immesenly frustrating. I quit this years road WCS because of it, and dozens of other top level drivers have done the same thing, for exactly the same reasons.

AC is far superior in the tyre physics department.

 

Yeah, it's not final, but from what I hear iRacing's is never finished either, they keep tweaking from season to season.

 

As far as tyre model itself goes, I'd say LFS has best one.
It has some big flaws though - as tyre temperature handling is all wonky.
But, it has (what others are missing) tyre flexing - which is missing in AC, and other sims.
To be honest, tyre feeling is still best in LFS (well, at least for me). Though, as said, LFS has some issues too... which will maybe be fixed in some 10+ years
However, AC is next in line out of other bunch.
iRacing has really weird feeling. rFactor is decent, but below LFS/AC.

 

Kunos are make simulators for ACI CSAI official italian school for single seaters that has HQ at Vallelunga, so they are no "street punks" themselves http://www.assettocorsa.net/forum/index.php?threads/driving-in-formulaabarth.1762/page-8#post-28501

 

Why I feel that most of these comments are not based on objective judgement, but superfluous theory making.

The very idea that LFS has the best tire model out there, is a joke. OK, it bends, but that doesn't mean anything. It could be just a visual thing.

Don't afraid do admit that you have no idea what's under the hood.

Maybe some AC dev could help us out here.

 

No one said, that they are street punks, but they are a small team and probably have no resource (yet) for doing years of research on advanced tire behaviour.
The kind of job that Kaemmer did.

 

AC simulates tire flex! It's just not visually. But the model behind the tires takes the flex into account.

 

Everyone will always prefer one sims physics over another, I havent driven the latest I racing TM but to say they are the best and the guy clearly know whats best but has needed 6 NTM versions and many other sims and all those up to NTM4 I personally hated. The RUF has apparently been a good step forward going by the comments and it seems they are finally on their way. Ironically many strongly defended each of their earlier tyre models when even they are admitting how flawed it was by having so many revisions.

LFS was good in its day but its quite outdated, graphical flex doesnt say much but it along with RBR are still pretty solid.

I think RF2 may technically have the most detailed tyre physics and yes they also have graphical and phsyical flex included. This doesnt meant it still feels the best with only the karts actually feeling like realistic tyres. RF Pro is still one of the most commonly used sims in professional racing teams including many F1 teams. I think the model has great potential but the actual implementation with most ISI content and over exaggerated real road kind of let it down.

AC I think is a big step from NKP, to me feels the best especially on the limits only the RF2 karts give me the same type of feel allowing you to throw cars around. This doesnt mean its the quickest way but as in most real cars I have driven it not like in many sims where there is max performance then nothing. You can normally go way beyond the peak tyre grip it will just slow you down lots. Any car should be able to be driven sideways to a point and to go quick in most of them you need to real this in and stay clean. AC still has a long way to go in other parts but tyres are on the right path as is the handling of cars weight which I think is the other part it really stands out from the rest.

No tyre model or sim is perfect or even close to it, eventually as they are all trying to simulate the real thing they should all end up quite similar even if they have different ways of reaching a similar end result. The main thing is that a car should have similar performance to its real twin and also you should be able to just jump in and drive. There should be no reason to need to re learn the physics in order to drive any sim. If you have any real track experience then it should be a natural feel but there are obvious limitations with the setup and hardware we use. Of all current sims AC still has this natural feel the best for me though I do try them all as they are all getting better now. The ones I really don't like I just want run much but glad to support all devs as the more competition the more they will push to try and outdo the others to our benefit.

As long as they strive for realism and not simplified arcade physics to keep the kids entertained then the extra competition should be welcome by all sim fans.

 

You can probably have the most complicated model and still dont get it right. Its when the tire
gets stressed the problems begins. In iracing the tires overcook in a way that I dont like.
The gripp will gradually lose or regain traction in a way that it would in real Life to get
god in my book. Asetto does this better than most off them. In iracing you get to a critical Point
when you have it and then lose to much at once and it will not respond enough when correcting or
reducing speed when the actual sliding begins. And the real problem is when this critical Point
cant realy be senced Before it begins.

 

What bigger appraisal of Kunos's approach would you want? Big racing school choosing their simulator is not good enough

 

In AC I can actually feel the tyres, for me other sims I don't have that .

Too cold, hot, different types and compound it's like wow I can feel the difference. I hardly need the tyre temp monitor, just try and brake, you can feel how warm the tyres are. Drop the tyre pressures a lot and you can feel the side walls swaying. Previously I've found driving sims to fun but basically a string of exploits, you're controlling a car with a wheel but what happens only has a passing similarity to real world driving. With AC I feel I'm closer to just driving, not gaming the game to go fast.

I love driving in real life but although I've enjoyed previous sims I haven't felt inspired to drive for hours, but that's how I feel with AC