“ are rfactor2 physics broken” video

Discussion in 'General Discussion' started by GTClub_wajdi, Dec 29, 2020.

  1. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    Although pressure tends to be measured at rest, with the wheel on the car (loaded). If you make it 0psi off the car (open the valve, nothing happens), then put it on the car, it'll have a reading and air will bleed out. Then you get to 0psi. Will the rim be riding on the rubber internally? Depends on the tyre and load...

    In other words: depends! :p
     
    Bruno Gil likes this.
  2. Yzangard

    Yzangard Registered

    Joined:
    Dec 6, 2018
    Messages:
    351
    Likes Received:
    173
    Since first post or almost the question is about GT performance, so I stand with this idea. You realise you didn't mention the car or the track ? And since graphics are failing, we can't even figure it on the video.

    Anyway 0 Kpa only means the pressure inside the tire in the same as outside, not that the tire is flat...

    Could you also show telemetry with actual pressure to see how it evolves ? Maybe should spot something here.

    But yeah, should be worse than that.
     
  3. Raintyre

    Raintyre Registered

    Joined:
    Jul 28, 2013
    Messages:
    200
    Likes Received:
    155
    Yes, there was rolling resistance in RF1, and i remember rising tyre pressures was a key to not lose too much straight speed on certain tracks, and obtain better lap times.
    Also, in RF1 you needed to rise pressures to cope better with high speed corners, and that was also important on certain tracks. Because more inflation protects against deformation and reduces load sensitivity.
    I think we have the right to demand some basic features that an older software had.


    >>>>>we've agreed in the past that some extra parameters would help complete the tyre situation, without the need to actually rework the base physical modeling.

    I agreed but I was wrong. If you alter grip depending on temperature on StaticCurve (penalizing more the cold temperature) you will alter a lot the handling, because the tyre grip changes too much in just some tens of a second. Then you can't apply that workaround without changing how the car feels and reacts.
    Apart from that, the workaround doesn't avoid that using lowest pressure setting is always better.


    >>>What I don't agree with is the premise that the lowest legal pressure (say, 110-130kPa) in a given car/mod shouldn't produce the fastest laptimes. (ie making a low pressure unusable in a competitive sense, is more nonsensical than the lowest allowable pressure always being fastest)

    There must be a window. If there isn't a window then it doesn't make sense that you have settings to choose. With current situation, only one setting is chosen, because if you choose a higher setting you will be slower....
     
  4. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    To me that only suggests either the staticcurve needs more flexibility (make it a lookup table instead of a 3-point curve), or, the effect you're trying to get shouldn't come from staticcurve.


    There 'must' be a window if in real life there's a window. If the real life series limits you to a minimum of 22 psi, and everyone runs that (and even heats their rims when measuring that, so pressures don't rise as much on track), then having a sim that doesn't reward doing the same isn't a sim.
     
    Bruno Gil likes this.
  5. Raintyre

    Raintyre Registered

    Joined:
    Jul 28, 2013
    Messages:
    200
    Likes Received:
    155
    Unfortunately we don't have punctures in RF2 either :D... I abused of this word, it is not punctured, but of course the effect of a 0kpa "inflation" is the same: flat tyre.
     
  6. mantasisg

    mantasisg Registered

    Joined:
    Aug 17, 2016
    Messages:
    2,425
    Likes Received:
    3,284
    I see this discussion is pretty hard, mostly because no one has ever attempted a top speed run with flat tire. And I think no one will ever do it. But that is just my assumption, I like making assumptions. Perhaps someone out there is crazy enough to do a dabble at this, it could also work as nice "Jackass" style idea for youtube: "Flat tire top speed attempt gone wrong".

    I found some tests actually, but they only dared to do so with special runflat tires, perhaps those are what is simulated in rF2 :D

    "Only 15seconds slower"


     
    Pawel44 and Raintyre like this.
  7. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    I attempted to run a quasi test in ttool with a normal load and very low pressure (2kPa), I believe this particular tyre is a bias ply (it's from the database). I probably should have done a target load rather than setting the ground height manually, I thought 4.5cm compression was going to be close to my target of 2500N load but only ended up on 1835N.

    What's clear is that first, it's not running on the rim, but also the majority of tyre wear is going to be near the shoulder. Not hard to see where the extra heat is coming from either from the side-on view.

    upload_2021-2-14_10-56-50.png

    (triple screen resolution; best to 'view image' or equivalent to get the full resolution)

    Realistically I think it's reasonable to assume in real life this tyre would fail fairly quickly, through temperature and wear at that peak stress point out at the shoulders (note the cross-sectional view on the right hand side). We know rF2 doesn't do that sort of wear or structural fatigue though.

    It's a shame we can't see more than a single tyre wear figure, because it hides the likely side effects of running a tyre like this in terms of uneven wear (and degradation at the focused contact areas). I haven't done any grip testing in ttool or the game with this sort of ultra low pressure, it's kind of hard to believe even with rF2's shortcomings in the tyre model that this doesn't produce considerably less grip than a normally-pressured tyre, and that difference would spiral out of control as rubber degradation kicks in.

    Extra rolling resistance would indeed seem logical, but I think you'd also want some puncture mode of failure for tyres, and some sort of reasonable puncture/delamination effect too (in terms of graphics and handling)

    For me this particular pressure shouldn't be selectable in the game (and I doubt it is, unless there's a crazy mod out there) so you don't even really need to allow for this sort of scenario with an intact tyre. You shouldn't reach this sort of state unless the tyre has already failed, and then all bets are off because the air that is being held in there in my test is probably the main thing keeping the rim off the track.

    So, having actually done a few little tests, I'm now arriving back at the core question: does the game actually need to model this correctly? The only reason I can see you'd need to handle under about 100kPa in any normal tyre is in a slow leak puncture situation, and I suspect in that case you could handle it with separate specialised parameters (with some sort of accumulation leading to a complete failure, for example).

    (I should also point out, this particular tyre and it looks like close to half the database tyres as well, don't have GaugePressure=0 in their suite of quasi tests. I believe extrapolation is limited after some spectacular failures early on in rF2, so if a tyre doesn't actually have tests run at that low pressure to build the lookup tables the effect will probably be a little off. But as above, I don't know how relevant this all is anyway)
     
    Last edited: Feb 14, 2021
    TJones likes this.
  8. Raintyre

    Raintyre Registered

    Joined:
    Jul 28, 2013
    Messages:
    200
    Likes Received:
    155
    Nice one. At 1:48 there is some description. For the lazy ones i will write it, sorry if I make any English language mistake...:
    "You won't get four flat tyres everyday, but if you did, you would find it impossible to drive more than a few yards... Then things generally get nasty".

    I found one, also using special runflat tyres to show temperature. At 80kph the temperature difference was already 35ºC. Which difference can we obtain at 300kph on standard flat tyres, in case we really could reach that speed before crashing? Imagen2.jpg

     
  9. Raintyre

    Raintyre Registered

    Joined:
    Jul 28, 2013
    Messages:
    200
    Likes Received:
    155
    That's ok, but it is not enough with stablishing same limits as real regulations. Because that's only the start pressure, but it will change once the car is racing on track (normally will increase). A complete simulation should replicate same evolution of the tyre pressure during the racing time, and also replicate the same effects that the evolution of pressure has on grip, wear, temperature, ride height, handling, etc... Because in real life those effects are not neglectable, are noticeable and have an impact on lap times, and in the way the driver must adapt to them and take them in account when doing a car setup. It is possible that too low pressure after caution laps caused Ayrton Senna's accident. Low pressures must have some advantages, but also some disadvantages.
    What if aerodynamics efficiency was badly calibrated and you had to run always the lowest wing availableat every track, no matter how many corners or straights, what would be the point? What would be the simulation value? Why do high downforce settings exist? Because in some tracks and conditions, it is better to run high downforce settings, you can do better lap times if there is a lot of corners and short straights. But in other tracks you must choose low downforce settings, because you can make more profit of their advantages on long straights, etc.
    That's the joy of simulation, have realistic physics to play with and understand them, and see a minimal correlation with the real counterparts.
    There a lot of games out there to accomplish our wettest fantasies.... Rfactor used to be a simulator.
     
    Last edited: Feb 14, 2021
    TJones likes this.
  10. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    @Raintyre I agree with basically everything you've said there. Thing is, for the last 4 pages all you've been talking about is very low pressures, so that's all I've been talking about.
     
  11. Bruno Gil

    Bruno Gil Registered

    Joined:
    Oct 12, 2020
    Messages:
    115
    Likes Received:
    73
    As I've pointed out before, I also agree that there is some fundamental fault with the tire pressures. After reading all this, more experimenting and more thinking, here's my current take on it:

    It makes sense to me that running pressures lower than ideal has one major drawback: temperature build-up due to excessive tire deformation (particle "rubbing").(Let's ignore "ridiculously low" pressures for now, that has one major drawback being the failure of the tire, and that is best fixed by adding a script into the existing model imo, or just plain blocked from using such pressures as most sims do).

    Now this in and of itself is, I think, not a big enough downside to kill the gain from the increased contact patch, IF you can keep the temperatures in control. Here's where rf2 really differs from other sims: running pressures too low doesn't overheat the tires. And I have an idea on why, based on another known fault with rf2: asphalt temperature has absolutely no effect on tire temperatures or pressures.(I've taken this for granted for years,I might be wrong, let me know if this is the case).

    You can see this in other sims. I remember for example in AC I had a race in nurburgring, and practiced for it with the default settings, which would be something around 25c track temperature. Then come race day, and the server was running real weather, which meant the asphalt was a chilly 3°c since it was a cold day there (surprise, lol). This meant I HAD to lower pressures - to the minimum nonetheless-to keep temperature on the tires, BUT it also meant that once the tires started working I had a lot more grip to work with.

    This fits with what I believe is wrong : the reason I believe you have to run higher pressures on hotter asphalt is because of the lower heat delta between tire and road* causing lower thermal transfer/cooling of the tire, which means heat build up. Since this has no effect in rf2, its like driving on chilly tarmac the whole time, so the tire never overheats.

    Thoughts?
     
    Pawel44 likes this.
  12. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    It's my understanding - and I certainly could be wrong, but last time I tried I couldn't find a direct quote from Marrs or someone else to back up either opinion - that track temperature does interact with tyres (ie the tyres will lose heat to the track), but the track temp itself is a static 26-30° (somewhere in that range; not sure if there's an exact reference around. ttool seems to default to 30).

    So changes in ambient and reported track temp won't change what the tyres are doing.

    BUT, in terms of tyres heating up with lower pressures, and heating up less with higher pressures, I don't think the track temp is too major a factor. I mean, most racing happens with a track temp range of 25-50°, and above Raintyre I think had a 7° difference in tyre temp between 160kPa and the floor pressure (he set 0kPa, but I suspect the tyre itself has a minimum test pressure of 50-60kPa).

    Therefore, as far as temperature variation goes, I don't think the track is a major factor in this.
     
  13. Bruno Gil

    Bruno Gil Registered

    Joined:
    Oct 12, 2020
    Messages:
    115
    Likes Received:
    73
    While my experience with this is limited to other sims, you can test this for yourself with ac or acc: if you set the pressures too low the tires will overheat and get out of control within one - four laps, depending on how much you abuse it, and how hot it is. Try >30c ambient temperature and you will surely notice it. This is best tested with soft tires which will respond to heat much faster. However, if you set ambient and track temperature very low, say below 10c,you can get away with much lower pressures, sometimes minimum.
    I know, it's a sim and all, but let's remember both sims I mentioned use empirical tire models, hence the numbers should be theoretically correct.

    The near static track temperature could very well cause this, especially considering that, since ttool expects a static temperature, it will most likely default the tires "best behaviour" to that temperature.

    Can you change that default in ttool to 0°c for example?

    EDIT: actually, this all fits with raintyre's rolling resistance point: rolling resistance IS the conversion of kinetic energy into heat caused by the deformation of the tire, or at least that's my understanding of it.
     
    Last edited: Feb 14, 2021
  14. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    9,606
    Likes Received:
    4,617
    You can, but I'm not experienced enough with ttool to run any tests and see how much it differs; my point was that as things are, having a variable track temperature won't help because even a massive pressure change (100+kPa!) resulted in a 7° temperature change. I do get what you're saying though - if the track temp did change, and that impacted tyre grip, the lack of tyre temperature variation with pressure would be a glaring issue - because a somewhat ideal setup just wouldn't be possible in anything but the average conditions. In that scenario it may have been altered, but here we are.

    Well, I wouldn't say they're the same thing, but linked for sure.


    Just to side step, testing tyres in devmode in an entirely different capacity earlier, got Sebring in there and set the track to fully wet. And got reminded, again, that we have these lovely looking puddles but they don't represent the physics at all - instinct says avoid the puddles, but they offer no less grip than the merely damp tarmac next to them. This is the sort of glaring oversight (obvious from the cockpit for a newbie) that really gets frustrating with rF2, and for me is a bigger issue than some excessive sliding that some fast drivers are able to do. This tyre chat is there as well, because someone with real life experience may well want to adjust pressures to help control temperatures, and might also want to check tread depth across the tyre... oh! Can't do that either! :rolleyes:
     
    Bruno Gil and Pawel44 like this.
  15. Yzangard

    Yzangard Registered

    Joined:
    Dec 6, 2018
    Messages:
    351
    Likes Received:
    173
    35°C after 90 km or 7°C after less than 5 km (impossible to tell exactly) seems reasonable after all. Speed difference is of course a factor.
     
  16. Highlandwalker

    Highlandwalker Registered

    Joined:
    Nov 11, 2016
    Messages:
    547
    Likes Received:
    1,640
    How much longer is thread going to continue, it's just going around in circles. If every thing got implemented that people are moaning about no home computer would be capable of running it. I agree exploits are wrong, it's cheating no matter which way you look at it, just make every body run default set up for online races or leagues so it's fair and it's down to driving skill and practice. The fast driver will still be fast as in real life but at least it's not cheating and just down to driving skill. Until the exploits are removed I think this would be the fairest for every body, anybody found using them should be disqualified, not sure how it could be policed though. I don't play on line because I don't want to race against cheats. I know a lot of you will disagree it's just my opinion on the subject.
    All exploits should be publish so S397 can try to remove them for the future to make it a better sim for us all.
     
  17. Remco Majoor

    Remco Majoor Registered

    Joined:
    Apr 22, 2014
    Messages:
    812
    Likes Received:
    884
    First off, they are allowed to talk about it, if it doesn't suit you, don't participate.

    Secondly, just because you think it's cheating doesn't mean it is. I look at it this way. The games physics are the rules, and drivers are trying to go as quickly as possible within those rules. Since they are not altering the physics, they are not cheating. It of course would be if, as you said, there was a rule against doing a certain thing. But that brings me to my third point.

    How would you write the rules for these exploits? There are already rules in place for for example tire pressures, cambers, and all the setup options really. It's in the mod itself. You can't go lower than 140 KPa in GT3 cars for example. For the excessive slip angle, do you want to limit the amount of slip angle that a driver is allowed to have? Drivers are not allowed to understeer? I am genuinely interested in how you see this in your mind.
     
  18. mantasisg

    mantasisg Registered

    Joined:
    Aug 17, 2016
    Messages:
    2,425
    Likes Received:
    3,284
    Also it is not going circles, we keep finding different things to talk about. It is not a bad thing, it is interesting. The only issue is that the thread carries that clickbait title, that isn't even grammatically correct.
     
    Bruno Gil likes this.
  19. Highlandwalker

    Highlandwalker Registered

    Joined:
    Nov 11, 2016
    Messages:
    547
    Likes Received:
    1,640
    If OK so why is every body moaning about it then. If every body ran the default set up for on line we would really see who the fast drivers are. I suppose you could call it a form of BOP and every body wants that for the cars. If it's ok why were so many sim drivers faster than real life drivers at the virtual Le Mans because they knew how to use the exploits and that 's why each team had at least one sim driver to show the real drivers how to drive with the exploits. I know the exploits are with in the game but some of them go against logic.
     
  20. AMillward

    AMillward Registered

    Joined:
    Apr 4, 2017
    Messages:
    1,810
    Likes Received:
    1,754
    Its not cheating because everyone can do it just by making a few clicks in the setup screen. It’s no different to Brawn and the double diffuser, or Mercedes with DAS.

    running external exe files for more grip and power, now THAT is cheating.

    as for Le Mans and showing the pros how to drive with exploits: we didn’t. Jenson, the Priaulxs, Max Papis all drove “normally” and were still damn quick.
     
    Bruno Gil and Dawid Mroczek like this.

Share This Page