Traction Levels Between Sims

Discussion in 'General Discussion' started by vegaguy5555, Mar 21, 2017.

  1. peterchen

    peterchen Registered

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    You know anything about racing and how tyres work? Seems not.
    If tyres are toasted or not at high steering angles depends on speed in given corner and of throttle input (provoke undesteer).
    Why do you defend AC here with tooth and nails? If you like it better than rF2 (of which forum that is) then go play AC!
    Simpel as that! :rolleyes::rolleyes:
     
  2. QUF

    QUF Registered

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    You've taught us a lot about simulation with your post, thanks. You're asking me why I defend AC, I'm simply demonstrating what AC does to counter what some have written here since usually what I've read doesn't really apply when you go test in the game. People here say x, but when testing in AC happens y.

    All sims are wrong because they aren't exactly like rf2. Those are basically all the arguments I've read in this thread. That sounds like religion. All the arguments I've read so far for what AC does is wrong because is not exactly like in rf2.

    What tests have been done to check which sim does it right in the parts they simulate or if all sims do it wrongly compared to real life? Nobody ever questions rfactor2's simulation, right? Is it because you've already tested it technically to real life or no one has actually tested? Show us,. based on real life, that what rf2 does is right and all the other sims, or in the case for this thread Assetto Corsa, have it all wrong. No more empty arguments and exaggerations, show us. If you can't, then stop assuming one sim is right and the other is wrong.
     
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  3. QUF

    QUF Registered

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    What does the number above each tyre representation mean, in the lcd hud on the bottom right? The core temperature?
     
  4. hitm4k3r

    hitm4k3r Registered

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    Usualy discussions get unhealthy when people start posting RL videos to prove their point. But to actually bring some seriousness to this discussion, I watched the whole video and nope - he never went beyond 90 degree steering lock through Eau Rouge as you did it. It's a fine nuance, but it makes quite a difference to tire temps how you engage highspeed corners and how much steering lock you apply. One could argue that all this is dependend on steering lock and car setup - so in that regard I have to agree with you to some extent, but the problem is that we don't have much information given in the video besides watching a driver driving. The most important thing missing being tire temps, the subject that we are discussing in this thread. We have zero information on his tires, his laptimes and about his general car setup nor the length of his stint. As said, the rF2 video is pretty old and tire temps behaved quite exaggerated in extreme conditions - even buggy if you watch closer, wich isn't the case anymore with the CMP tires. What I am trying to explain to you, is that a tire is much more dynamic in how it builds up and transferes heat opposed to what AC is currently showing accross the contact patch, in the core and different parts of the tire. This is a problem in how you can abuse tires or how tire managment affects your strategy, so for me it makes objectively a big difference and not because I just prefere one or the other. It's a technical decision for me. In AC it makes not a big difference to me if I lock up the tire or not, because there is no physical flatspot wich will violently shake my wheel and affect my laptimes, it's a certain amount of tire-health that I lose nothing more.For some people those nuances don't have much importance, but for me they do.

    So as Marc G said, I enjoy driving both sims and it would be a far stretch to call AC bad, but objectively speaking rF2 is closer to what you see when you take a look at thermal cameras showing tires in race conditions. And yes, temps can go up the sky like a rocket:



    Also keep it civil guys. We are trying to have a technical discussion, don't we? There are few other very nice videos showing temp development of tires. Don't underestimate the influence of load and friction. :)
     
    Last edited: Apr 23, 2017
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  5. 2ndLastJedi

    2ndLastJedi Registered

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    I love how these tyre topics go, lol all you tyre tech from Michelin and Pirelli i guess.
    When someone can come here and tell me that they are Lewis Hamilton's tyre Engineering then I'll listen until then I'll drive and be happy with what I've got because both "Games" are better than any game i could ever make.
     
  6. patchedupdemon

    patchedupdemon Registered

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    That's the same video some of us used on iracings forum to question Dave kammers logic,he said that air hardly cools the tyres,and the main cooling mechanism is thru contact with the track.
    Some more knowledgeable than me stated that the tyres are still generating heat on the straights,but he then said that the track absorbs my heat than it generates on the straights.
    Off topic i know,curious to know your guys thoughts on this,by the way,someone did a very simple cfd test to prove him wrong,but still the fanboys ignored the test and sipped on his foot cheese
     
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  7. hitm4k3r

    hitm4k3r Registered

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    That's a strange logic you apply there. You don't have to be a tire engineer to form an opinion about this topic. Alot of the stuff that I picked up is by following motorsport for more than 20 years, listening to experts or interviews and reading up the stuff that I am interested in or asking questions. When you read Michael Bordas dev blog about tires you can learn alot too. You don't need to be a car mechanic to be interested in cars. What I can tell you though is that rubber gets extremely hot compared to it's cold state, when it gets under heavy load and friction. You just need to watch a MotoGP race to see what happens when rubber is sliding over asphalt at high speeds and when rubber gets burned literaly. The reason why those thermal camera videos are nice is, because they show how temperatures fluctuate under race conditions on the tire surface, something that was questioned or labeled as to be too excessive.

    @patchedupdemon: that's actually an interesting question that I never really thought about. For one thing it depends alot on the ambient temperature. What I can tell you though is that air transferes/adsorbes heat alot less than asphalt, so that speaks for Dave Kramers logic. It's also the reason why track termpartures are alot warmer than air temperatures for example - in most cases atleast. What makes this interesting is that the ambient temp has not so much effect on the tire temp itself but how the track heats up and interacts with the tire. Note that I am simply going by comparing the thermal cunductivity of different materials. The effect of cooling or heating of materials is also dependend on the area that is affected so stuff like contact patch and rolling resistance of the tire values in aswell. (https://en.wikipedia.org/wiki/List_of_thermal_conductivities). Next to that comes other stuff into play like cooling effects of wind etc. That's how I would explain it to myself and I personaly think that Kramer has a point when you just compare the thermal conductivity of the materials, though just making a simple calculation with a simplified tire shape would be something usefull. Someone can correct me if I am totaly off there. ;)
     
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  8. peterchen

    peterchen Registered

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    lol
     
  9. patchedupdemon

    patchedupdemon Registered

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    A lot of folks said basically what you just did to back up davids claim,but that is also claiming that on the straights, the track/tyre interaction is not creating any heat,or Not enough heat to over come the tracks ability to absorb the heat.
    This is where the cfd test proved the claim wrong to,as David claimed that hardly if not any heat is created when just driving straight at 200mph.
    But if that's the case,as heat is generated by wear/slip etc,why would the Bugatti veyrons tyres only last 15 mins at full chat.
    I still don't know the correct answer as David didn't really give any proof to his claims,and didn't challenge anyone who challenged his theory.
    I've been trying to find the answer but,it's like trying to find a unicorn

    What I don't understand,when looking at how much of the tyre is in contact with the ground(contact patch) compared to how much is being hit by air,my weak brain just tells me,air is the biggest cooling factor,I just can't see how the track can cool a tyre when the contact is generating heat,the only way I could see that happening is if the track temp was way way way cooler than the generated heat at contact,and heat inside the carcass
     
    Last edited: Apr 24, 2017
  10. 2ndLastJedi

    2ndLastJedi Registered

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    Same with most on here Myself included but i also have first hand experience not just from watching cars on TV, also i'm pretty sure that just about everything you've read about tyres i've read also .
    But anyway , as you state
    "to form an opinion about this topic"
    We all have this same thing , an "opinion" . Enjoy yours .
     
    Last edited: Apr 24, 2017
  11. hitm4k3r

    hitm4k3r Registered

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    The question is, whether the opinion is based on reliable facts or not. It's the same situation, when people thought that the tire flex in rF2 is too extreme. When you actually watch a super slowmo of racing tires in action you can actually see this, so in that regard rF2 is objectively pretty much spot on. Same goes for people questioning big tire temp fluctuations. The video I posted, actually shows that exact same behaviour, so objectively speaking, it's a fact that tire temps can go up the sky if you apply a certain load or friction. Another famous example is people complaining about too strong rattle caused by flatspots, when in reality flatspots are a serious problem leading to extreme vibrations and collapsing suspensions. Objectively the reality is speaking against those complaints. Those are simple facts and not my opinion. My opinion is, that rF2 exibits those situations very well though in the limits of it's simulation.

    @patchedupdemon: as said, I need to think more about it and calculate an example with with a simplified tire shape. Especialy the contact patch between tire and tarmac or between tire and air play an important role the more I think about it, so you need to take a look at the relation of those contact patch sizes. Note that my example with the thermal conductivity was very simplified completely ignoring any tire movement and wind, let alone thinking about it's correct shape. It is a very complex topic, being dependend on many different variables so for me it is difficult to form a well educated opinion. I would be interested to read about that cfd though. There are alot of things that you have to take into account.
     
  12. QUF

    QUF Registered

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    Why no answer? For example you start in the pits with the lcd app showing 75 for each tyre. Is this number an average, core or surface temp, contact patch temp? But I think the number we see in rf2 for the tyre doesn't represent the same numbers we see in AC's tyre app (which has: core temp, surface i-m-o).

    Why are you judging what I did on the first lap with a gamepad? So what if I steered 90º between eau rouge and raidillion on cold tyres with a gamepad since I can't use my wheel now.
    The surface temperature quickly rose in the ballpark of 20ºC just by taking the hill at high speed with 90º steering for brief moments. How can you say is wrong or right? Should have the temperature risen 50º in a matter of meters?

    About all those thermal recordings for videos. Those aren't exactly the type of surface temperatures sim racing games simulate. The surface temps in sims are deeper in the tread and not on the actual surface that is in contact with the air. Therefore the readings we see in sims is less volatile than the readings we get from thermal cameras. Devs don't develop tyre temps from readings such as you see in videos, therefore is wrong to compare what you see in the video and what you get from the sims.
     
  13. 2ndLastJedi

    2ndLastJedi Registered

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    Agree .
     
  14. SPASKIS

    SPASKIS Registered

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    What heats the tires:
    -Friction with the track due to sliding.
    In straights convergence in combination with tire load/pressure (contact patch) causes sliding. The little slip angle is small in this case.
    In turn, tire sliding is huge compared to straight. The contact patch has relative displacement at some point even for perfect steering system accounting for the different paths inner and outer tires carry.
    -Hysteresis of the tires. I am not sure how much contributes this. It will depend on the plasticity of the rubber.

    As a summary tyres heat due to friction with the road creating thermal energy. The thermal conductivity helps releasing part of that heat to the track. I dont think however, that the cooling due to forced convection with air is negligible at all. A coefficient of above 50W/m2K should be considered. For a 80 degree deltaT, we are talking of at least 4kW/m2. Current F1 front tires have a rolling surface of 0,3xπx0,67=0,63m2. In total about 2,5kW.
    I really doubt that such an amount of heat can be transferred by conductivity considering a deltaT of about 70°C and a contact patch of around 0,3x0,1=0,03m2.
    A heat flux of 80kW/m2 would be required to extract an equivalent amount of heat as by air convection. That's 20 times more than the calculated value for the forced convection.
     
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  15. vegaguy5555

    vegaguy5555 Registered

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    Tires heat and cool quickly mostly for one reason. Energy from friction. Take away friction/energy, tires will cool quickly. So that means a tire will go from melting to very sticky in a short time. Drag racers use this all the time.

    I have yet driven a sim which gets this right.

    rF2 comes the closest but you can see in my video when I depend on the sticky part of the drift when I let off the fuel the tires stay melted when they should be getting sticky. This throws my timing off.

    I can't even begin to explain what AC is doing.
     
    Last edited: Apr 25, 2017
  16. hitm4k3r

    hitm4k3r Registered

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    Now we are getting a bit closer to the problem. First of all I don't know if you play with a gamepad or not. How should I know this? It still doesn't change the fact that your imput leads to tire scrubbing and is anything but healthy for a tire. Note, I didn't see Müller turning his wheel in the video as much as you did either, but it's a quite obsolete discussion as the Spa video of Jörg Müller driving shows us basicly nothing that is of relevance for the matter of tire temps nor does it give any technical information - how often should I repeat it? What I go by is some simple logic that you can use accordingly. When I see people applying allmost no lock with semi slicks in normal race conditions raising the surface tire temps easily over 20 Kelvin in normal race conditions within the limits and slow corners, I just count one and one together and know what happens when you scrubb a racing slick in a high speed corner under extreme loads in corners such as Eau Rouge - and I think you will agree with me on the fact of this corner being extremely stressing on the tires - over the asphalt. Remeber the tires blowing up last year in F1 at Spa?

    I tested the same corner in the Camaro GT3 in rF2 and getting the tire scrubbing over the asphalt through Eau Rouge gets you easily over 100 degree. If you think that 20 degree are realsitic, so be it. I am not here to convince you but just to tell you what I am seeing in rF2, AC and in thermal camera shots in real life.

    Regarding the thermal videos: what makes you so convinced that the rF2 tire temps aren't showing the exact same thing? For a person arguing so desperately you don't seem to know that much about rF2. How about testing stuff like that on your own before make a final statement about how temps are shown in sims? Little hint: it's showing the surface temp as those thermal videos. But don't try to compare it to the AC surface model. You can still see outer, inner and middle temp in the garage but it's fluctuating alot and not that simple as you might think. Might be worth to test abit more before arguing. :)
     
  17. QUF

    QUF Registered

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    For a person that likes to argue every single little detail about Assetto Corsa's simulation, you don't read what people say to answer accordingly. When I posted that video 1 page ago I told in what conditions I made the video and the reason for using a gamepad at the moment. Therefore you can't compare my driving to real driving, since my steering inputs with a gamepad will be different (for the worse) to driving with a steering wheel.

    Here's a post from a user that explains what are surface temps in the sim and in those videos.

    Unknwn: "Tire surface temps behavior in these videos and in AC seem to be far apart."

    Stereo: "AC's "surface" is thicker, it's not just the visible outside layer but the whole tread really, and then the core is the rest from steel ply through to the air inside. When people talk about taking shallow or deep thermal probe measurements of a tire that's closer to the layers AC uses.
    The actual amount of grip available depends on how soft the whole tire worth of rubber is so it's something more useful for simulation, rather than something close to what you can see on youtube."

    You simply don't have any technical knowledge about simulation of tyre temperatures, yet you constantly say that AC is wrong and rf2 is right or very close to reality. I don't have that knowledge either, but I'm not throwing stones in either direction. Maybe people will take your input with value when you post analysis with evidence between AC, rf2, real life. So far your arguments on what is right and wrong between sims are empty and devoid of any scientific approach. You only want to hold to your opinion that rf2 is better by far and is very very close to real life, no matter what other people say.
     
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  18. hitm4k3r

    hitm4k3r Registered

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    Why getting personal and throwing insults around you when you have no idea what the rF2 tire is actually doing? And going by Stereos response he has no idea what the rF2 tire is doing nor how the structure looks like. What does "the surface is thicker" actually mean? Is he talking about the tread depth? Maybe you should read up some information regarding the rF2 tire model before slinging with shit. FYO, I am not talking about grip levels but simply about temp development of tires under stress and especialy their surface temps. If you think that tires stay cool under stress I won't stop you - as said I don't want to convince you but I am just giving my personal impression of the subject. What I know is what happens if I crank the wheel and apply huge amount of lock in both sims, not just rF2 and how it correlates to what I see in thermal cam videos and how I get away in any of the sims. Those videos are basicly the best way to get an idea of the subject, because telemetry for racing tires is very hard to come by for obvious reasons. Anyway, the discussion is pretty much over now that you got personal. Have fun destroying your wheels. You seem to know it better. Bye :)
     
  19. SPASKIS

    SPASKIS Registered

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    Talking about traction. Very nice document this.

    Regardless all the technology involved in tires, some will always say that tire-track interaction is black art in order to justify whatever theory they defend.
     
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  20. RaceNut

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    That certainly should give us some idea of just how complex accurate tire modeling actually is in Simulation; where accurate tire performance data is not available, a lot of guessing may be going into the formulas.
     
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