Some thoughts about what could possibly be better with tires in AC

[mantasisg]

To everyone who is into simulation, and the pursuit of realsim. I mean realism.

(If you are fresh weekly content drooler, ten minutes "tryer", and judging cars physics by how perfect the model looks, then don't read)

Hello, I have been studying tires for a while. Studying them in AC, studying them in real life, comparing. Reading books, articles, works, observing videos and so on. I am definitely not saying that I know a lot about tires right now, but a little bit for sure. Tire, as Paul Haney writes, is one of the most complex devices.

I am not assuming that these things which I am going to mention are wrong in the code in AC, or they are wrong in the parameters of car physics .ini files, maybe those things are wrong in combined ways, or they are not wrong at all, just they seems so to me. Also in my opinion some cars are more believable than others, I don't know if some are nailed better by Aris, or the codes written by Stefano fits some cars better. I think older AC cars are better. But it must be mentioned that there are ton of official cars in AC, "kunos quality" is a known thing, and indeed overall AC quality is very consistent, but I hink that some things are just a bit better in some places than the others, especially speaking of such complex subject as vehicles physics, of which the tire is probably the biggest secret.

1. Tires grip falloff

In my opinion most if not all AC tires has too little falloff, or I could also say too much falloff grip. That thing alone makes driving much more zoned, drifting less of a thing. Every time you go too much over the slip angles or ratios, greater falloff makes you take more effort to keep the car in precise control, or in control. greater falloff makes rear end more tending to "run away" as you spin your tires out of slower corners, oversteering makes you move your arms faster, locking tires under braking is more of an issue. Transitions from oversteer to neutral slides to regained traction is more noticeable with also variations of back and forth - as you might have an oversteer switching to neutral little slide and back to oversteer again if you put the power down too soon...

Few little examples:

This twitchyness is very much the falloff of grip, cold tires makes it extreme.

Not a drift missile at all, even though obviously it loves slip angles, but it is not a drift car. Of course we could argue that there could have been oil, which ofcourse would make for great grip drop.

This is absolutely insane. Again lowish temps makes it more extreme, afaik it was 12C then in GW. Also you might say that we have more advanced GT40 with wider tires in AC, but I think it still should behave at least a little bit like that.


2. Tires load timing

Now this is rather complex. Tires doesn't react instantly to inputs, they have relaxation length phenomenon, also a bit of flex. Moreover, front tires are always a bit ahead of rear tires in terms of timing because they are steered, and.....in front. Rear tires has a bit of delay on top of fronts. Also often we have rear tires wider which also makes front vs rear tires behavior slightly different, and timing too. Relaxation length depends on load and slip angle, more load more length to react, more slip less length to react. Lateral tire flex is more influencing narrower tires, because logically particular amount of deflection will be more noticeable if it relates with narrower tire, visually and physically too. Tires load timing contributes to putting more effort in choosing turn in point, cars slides feels less linear, wheels feels more individual, coming back from slides gives slight speed wobbles unless you make inputs very very well. If a car has scrub radius flex and relaxation lengths can amplify it quite a bit.

Few little examples:

0:17 This Superperformance GT40 wobbles like crazy, it is combination of how tires falloff and then regain grip and the tires timing goes.

0:20 this old thing realy maginfying the phenomenons. You can see front vs rear are moveing very much on their own, they seem like they has their own inertia each and they oscilates in different way, it oversteers > understeers > oversteers > understeers till it clears the turn. I think many cars moves like this when on the very limit, especially if driver like to be a bit more rough, I think even modern cars does that, just with way lower, perhaps sometimes even invisible motions, well sometimes maybe very visible...


3. Grip and load sensitivity

I think some tires/cars in AC feels like if they have too low static grip and then too little incremental grip curve drop as the tires gets loaded very unevenly in high speed turns. Sometimes low speed bend feels a bit too slippy, and high speed bend feels a bit too safe. It is very tricky stuff, I am just thinking.

For example Nordschleife karousel is not a very fast corner, it also has very big banking in concrete part inside. So it is not a fast corner, and because of great banking tire loads will be more even, thats why you should be able to be surprisingly fast there, sometimes it feels that you are not so much in AC. Also it is concrete surface, in terms of surface it is not going to be more grippy than tarmac I think, adhesion might be better, but not mechanical keying - rubber penetrating irregularities.

Higher neutral grip, and more grip loss because of load sensitivity in combination with grip falloff levels and speeds plus manipulating wheels timing with flex and relaxation length might be a nice touch, and I believe a realism improving touch in many cases.


I am glad if you actually read it all, I know I don't have a reputation as someone who "knows things", but I think it is always awesome to think, share and discuss.

 

[McDev]

I also have the feeling that something is wrong but I also notice some people who just drive well so maybe it is just because I lack real world comparison and driving experience. For instance I tried to drift with a car and it either had a lot of grip or spinned out. I was only able to drift on lower speeds at dusty road conditions. I am used to drifting in snow so this was similar.

I also had problems to do power sliding, like you showed in the video seemed nearly impossible, it would just turn and crash to the wall. Here I have at least a bit of real world experience doing rapid U-Turns. The car would powerslide a little but not at all spin out.

I would like to use AC and other sims to train real life situations but I have the feeling that it is not the same either. So for instance at some corners my car starts to turn out slightly but stays at this angle and there is a resistance. Now there can be two things:
Either it is the Traction control holding the car on track and for obvious reasons I am not going to turn it off for comparison. I have seen too many Youtube videos where people crash their expensive RWD cars.
Or it is simply the lack of G-Force and other indicators that make it more difficult to feel this point in the sim.

In a sim I am often way too fast in a corner as I do not have a feeling for speed. Therefore maybe there comes a feeling that it is less controllable. So I thought that a given corner I could take with easy in my own car (an E81) but the 1M would understeer out of the track. Now for this thread I compared both corners on GoogleMaps and see yourself. I really got fooled by impression, and I was driving in VR. Maybe it is because the real track is much narrower and feels tighter ecause of that but the race track (BilsterBerg) also has a 180° turn which has to be taken slower of course. But in real life I believe that I would notice that and brake. I had one or two encounters of that kind at Autobahn exits where the turn suddenly narrowed...


I came to AC to try to rebuild my car by using parts and settings of the 1M and Z4. I actually planned to do some real world comparisons But I am not sure if I am even able to get the car right.

Anyway simulations can never be exactly like the real world, there are too many factors to come into play. Just small things like a car in AC does not idle when in Gear, it then runs at 0 RPM.
Also tire models is a controversial and maybe not fully researched topic. The iRacing forum is full of threads like this. At least this is much better than ProjectCars2, there I wasn't even able to get the car of ftrack, no Stability Control in the world could have hold it on track the way I was driving on heavy rain


PS: I am about to build a test track as I have not yet seen one like the Centripetal Circuit of iRacing. Just in case that would help you to make some tests

 

[mantasisg]

Gordon Shedden certainly is a top class driver, so if he spun out Etype trying to do a slide for show, then probably most would in such situation.

Do you powerslide in AC with TC on too ? Even light TC setting should be good help to keep the wheel under it's limit. I don't have much TC experience

True that we don't feel inertia through our bodies in simulation, but really the best indicator for oversteer is visual references, I find it the most helpful to be able to detect loss of traction by reacting to the yaw of the car, which can be felt visually, second thing is ffb. Having experience and expecting things to happen also helps a lot.

I have driven in VR just few times, and very little, but I also have overshot few corners I remember, lack of peripheral vision in VR maybe ? You are also more responsible in real life. So naturally taking less risk.

Your car idle in gear ? How is it so ? My car would stall.

I think AC tires are very good, I think they are second after rF2. iRacing perhaps could have better tire than they do, but it is a mess there overall, for example they have ruined Lotus 49 by giving modern tire for it, so it would be "more popular"... tires are indeed not fully researched, and probably will never be, also technically you can put whatever tire on a car, so it is completely possible to manipulate through tires a lot. But it also seems that simracers doesn't have any demand for more complex tires. And the saying "handling is great" is very skewed. Sure you don't want your sportscar to feel like a poorly made replica which is also broken, but you also shouldn't wish for flattened physics.

 

[McDev]

Gordon Shedden certainly is a top class driver, so if he spun out Etype trying to do a slide for show, then probably most would in such situation.

Right and it provides hope

Do you powerslide in AC with TC on too ? Even light TC setting should be good help to keep the wheel under it's limit. I don't have much TC experience

Sure it keeps the car on the track, I only like to learn to handle it without On 100% settings it seems to be unrealistic, especially at high speeds. So I mean it seems to just counter force and not simulating real stability control.

But what I mean is that even in lower RPM in 1st or 2nd gear if you hit down the throttle you should have some wheel spin at least, the back will slightly turn left and right and there is some smoke. I only see that at a complete stop and then it is rather smoke. At least that was my impression.

True that we don't feel inertia through our bodies in simulation, but really the best indicator for oversteer is visual references, I find it the most helpful to be able to detect loss of traction by reacting to the yaw of the car, which can be felt visually, second thing is ffb. Having experience and expecting things to happen also helps a lot.

For me that goes too fast. Maybe I am also just at the limit. When I try to make a clean race then I can counter react more often.

Your car idle in gear ? How is it so ? My car would stall.

Talking about a street car in AC when I am in N and standing and going in 1st gear it should idle and start moving slightly, but it just sits at 0 RPM but the engine is not off and there is no sound like it would be off.

But also some of those things I mentioned are not directly connected to a race simulator. I mean there are no indicators as well, but we don't need them. When I watch videos like this or drifting videos then it has to be fine overall. So if you just Race has to be great.

Like you said there are many factors and comparing with the real world makes it hard unless you have the exact same values. And that is something which will probably never happen. I mean at some point you got to simulate the whole chassis of the car and how it bends.

 

[mantasisg]

So you mean that cars doesn't stall ? Because they do idle, but they don't stall. Just drops to 0 RPM as you say, but the engine does not shut down. Personally I think that it is big thing for racing, because in some particular moments, such as if you spin you have to be aware of the possibility to stop the engine, that is important detail. The reason why we didn't have got to AC is that there were just simply too much cars already. I wish we had such small things such as punctures, engine overheating, stall, oil temps... would add to depth, maybe would be too much for average simracers, but there would be sliders anyway...

Indicators afaik are used by endurance racers.

Thats very nice comparison, I think AC is really good at that pace. IMO the most funky simulation is of car behaviour on slow speed manouvers, and near/over the limit high speed manouvers. In between of those extremes it is less complex... Also speaking of comparisons, I haven't ever really seen any truly awesome comparison which would focus more on the physics rather than appearance of circuits, car interiors... I also think that the most valuable are the external views, and the greatest value of all belongs to slowmotion videos and closeups, onboards are also good, but they are small piece of cake, but have been trending for a long time and I believe relatively easy to make, even such setups like Marcels.

Yes exact same simulation probably will never happen, and it is actually doesn't have to. But big essentials which are possible to notice purely by simple comparisons should set in strongly in a few next decades. True that parameters aren't exactly the same, they varies a bit, but it is not that slight possible mismatch will result in dramatically different results. I believe that each car in real life is different too, but they are still very similar anyway.

 

[McDev]

Also speaking of comparisons, I haven't ever really seen any truly awesome comparison which would focus more on the physics rather than appearance of circuits, car interiors...

That is what I tried to find. I thought there must be someone out there who does tests like this, trying to test behavior of cars on different occasions for different games, not just racing the driving line. Trying to do donuts at the finish line as this is something real racers do, too. But I didn't find anything like that. Does anybody know some place?

I watched Daniel Abt driving iRacing in a GT3 and while he meant that overall it is good that GT3 cars are too slippery. Maybe you can add subtitles. Maybe he also is just too fast like me as he would in real life

In another video he meant that setting up a car (in that case ProjectCars) is very hard because he does not know at which temperature the tire pressure setting is meant to be or which tire there is on the car.

Also usually real race drivers loose against sim racers. He attended a race where in the top 10 there was only one real racer. But it also wasn't top notch equipment.

 

[mantasisg]

Also it is way more valuable to try to find videos where cars are being lost over the limit, or are very close to being lost, that way you are picking up references for the car limits, and then you can try to have similar situations in simulation. I don't say that they has to be the same, but they has to be similar.

Surely it is nice to have comparisons of clean fast laps too, but those comparisons doesn't have very much value, even if they shows that car is similar, it doesn't show that effort is similar.

 

[mantasisg]

One more thing about tire grip.

Sometimes it could seem that a car doesn't have enough roll. It could be because tire has less grip than it should. There also could be some other reasons, but tire that grips a lot contributes to more weight transfer.

 

[mantasisg]

I am a bit sad that no one comes and says to me about many of those things from OP that "they are total BS", or "simply wrong" or so... I don't say that they are wrong and it is some kind of stupid social experiment, because it is not But I am also not claiming anything.

But it is pretty obvious that so many things about tires are just simply unknown, especially regarding the simulation. I bet that even the smartest guys, and with craziest knowledge about tires, still don't know A LOT of things. Tire is very fascinating device.

I know we have plenty of really really smart guys in community, but they just would never say that they don't know, perhaps they would only whisper..... while drunk..... while feeling sure that their personality is in secret....

 

[luchian]

I think it is a difficult subject, that's why not many people venture into it.

This is an interesting read on the topic:
https://www.iracing.com/physics-modeling-ntm-v7-info-plus/

After this read, I look at Kaemmer a bit different. In a good way. Even if I still dislike the business model.
Anyway, my highest respect still goes to Scawen.

 

[mantasisg]

Whoa thats lots of read, hopefully will have the time for that soon, just quickly scanned now. It deserves closer look.

I read that they see the carcass, and already can tell a lot about behaviour, then I read that there is some chemistry class about components of compound, and then that they do maths and science... Of course all of this matters, but at the end it is all down tomechanics of tire. So my first though was that their approach is too complicated, and not direct to the goal. Of course you can not randomly shuffle numbers, but I think that you can not calculate everything. Sometimes thats just coefficients. They do the job though. But I haven't read it seriously yet. I would like to read more stuff about direct ties between tire model/parameters principles and the outcome - the handling in the sim. Describing the things that cars does, and what are those things influenced by. THEN - after that it would be interesting to go deep into science, maths, chemistry - but at first physics, machanics, down to earth things

Rubber and carcass - thats a lot, but not everything. Dimensions influence, tread influence.... I think that type of tarmac at the contact patch is also a great part of a system - so it matters a lot to know how surface properties influence three sources of grip: mechanical keying, adhesion and the tearing of rubber as it slides (which I suppose could be interpreted as falloff grip). I think in future sims will have to have to have more sophisticated surface grip parameters, than just simply a general grip level.... That should introduce more realistic use of load sensitivity, also should help when implementing rain/oil.... as it is time when pretty much only source of grip comes from mechanical keying...Maybe ACC would do so ? Or something after that, if there will be something....

I wish in AC cars would have an option for totally different wheels rather than just compound.

 

[mantasisg]

I just have had some time to read that blog from 2010 which is linked at the beginning. It is quite interesting.

I totally dig that part about "scary zone" of slip curve. Well I think I do. IMO footage is very good reference for that, you just can see how cars are twitching, tearing-off after they goes too far out of the optimum slip zones, or as it is written in the blog "out of the racers office" It just simply is seen, although there might be many unknowns - like actual surface properties at the time, tire temps, actual pressures.

But I totally dig that they still needs numbers to fill in their theories. Nice to see that they actually goes all the way and actually does experiments to achieve such data, I have no idea how much such experiments costs for them, but honestly with such pricing I think they should perhaps even do more of it.

I have used iRacing for a while a couple of months back. I really liked Miata, then drove Lotus 49 and it was totally horrible. So IMO they has understanding obviously, they still fails majorly at some points. I think AC tires feels better, and IMO best tires are in rF2. Will be interesting to try new iR tire model after they will introduce it. And ACC too of course, even though only GT3's is a bit too narrow in terms of vehicles dynamics, they are so optimum by nature...

 

[Willy Wale]

I think the answer to FAQ number 9 at the end of that blog post is the most important. the tire models in all of the games on the market need to work in real time and on potentialy quite low powered hardware. Kunos and the others have to balance realism with processing time. each developer has to judge where on that continuum they pitch their offering.

 

[mantasisg]

Yeah maybe we could hope for quicker refresh rates. But I think that for purpose they are already pretty kool. Definitely maybe some day it will be so crazy that surfaces will be modeled to extreme detail, and physics will be able to read it for every single inch while going at top speed. But I don't think that it is essential, more like an extra thing.

 

[mantasisg]

When I was opening the tread, I was also speculating what improvements could be expected to be in ACC.

I must say ACC seems to have met everything, and more

 

[martinbrown9898]

Thank you for sharing, i love racing but with trucks, i am not a big fan of racing with sports cars, I have been racing with trucks for 3 years, also i am running a 24/7 towing service company so trucks are my love.