Exagerated tire heating at high load

Discussion in 'Car Modding' started by Oskar, Sep 25, 2023.

  1. Oskar

    Oskar Registered

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    I'm trying to figure out how to reduce or limit tire temperature at high loads.
    At extreme downforce levels when pushing the car hard in corners, I see extreme (non-physical) tire temperatures frequently, like above 200, when the optimum grip temperature is somewhere around 80-90.
    In reality the tire compound will boil off right at the surface before reaching these temperatures, taking heat with it, and effectively limiting maximum possible tire temperature.
    Also at higher temperatures it seems like there's some tire cooling effect missing, or just some coefficient that would need to be tweaked.
    Tire heating might be overestimated also, but I'm assuming that's a function of the tire simulation, so should be relatively accurate.
    Are there any tire modding gurus that could help point me to the variables that I should be tweaking?
     
  2. Robin Pansar

    Robin Pansar Member

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    To increase cooling of the surface temps you can change the values in this parameter.
    ExternalGasHeatTransfer=(8,4,0.6) // (base, mult, power) - heat transfer coefficients to external air = base+(mult*(vel^power)), where vel is linear velocity of tire

    I recommend increasing the third parameter as it'll affect cooling based on velocity. Many cars fail to have enough cooling on the straights.

    To reduce heat generation from sliding you can increase the second value this line.
    GroundConductance=(1000,0.003,0) // (base, mult, reserved) - thermal contact conductance coefficient to ground = base+(mult*pressure), where pressure is contact pressure and the reserved variable will be used at some later stage.

    You can also play around with these lines, where the third value acts as a fraction of sliding power applied to the tyre as heat energy.
    DryTerrainEffect=(0,1,0.5)
    WetTerrainEffect=(0,1,0.167)
    GrassTerrainEffect=(0,1,0.05)
    DirtTerrainEffect=(0,1,0.07)
    GravelTerrainEffect=(0,1,0.07)
    RumbleTerrainEffect=(0,1,0.5)
    SpecialTerrainEffect=(0,1,0.5)

    The values given in this example are a decent starting point. Just keep in mind to have the same fraction value in DryTerrainEffect, RumbleTerrainEffect and SpecialTerrainEffect.
     
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  3. Oskar

    Oskar Registered

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    This is very interesting! Based off the tgm generator .ods file, I would seem like the default is to apply 100% of sliding power to the tire as heat.
    That is just completely unphysical if the tire is being operated in a temperature and surface pressure range where it sheds compound material on the tarmac. But also, if the tire isn't leaving black lines, this should be a much more accurate assumption.
    It would seem to need to be a temperature and surface pressure dependent "multiplier" to be more realistic under all conditions.

     
  4. Robin Pansar

    Robin Pansar Member

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    Tyre temperatures are a really tricky thing to get right, and even know what is right. Real-life comparisons are very few unless you are one of the lucky ones to actually have access to some data. One decent reference that you have access to is some onboard thermal cameras of the tyres. There you can at least study the behavior of the contact patch and the heating/cooling of the surface.
    Some good examples:
    Rear end of a previous gen F1 car


    Front end of a previous gen F1 car


    Road car overlooking surface & internal temps, pressures
     
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  5. elgagon

    elgagon Registered

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    When F1 showed the thermal cameras, some teams complained about it, because they didn't want to show the real tyre temperatures.
    The FIA decided to show how the temperature changed, but the values were not real. There was an offset between the real values and the ones shown on TV (the real colours were different).
    You can see it here.
    It is strange that the tyre is hotter than the exhaust gasses.

    View attachment upload_2023-9-26_19-1-43.png
     
  6. Lazza

    Lazza Registered

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    I don't remember if they had values shown at one point, but the colour sequence and temperature range can vary - so while an image will show distribution of relative temperature, you can't compare two images. (maybe they calibrate them consistently, maybe they don't)

    Gas won't be picked up properly by the cameras they're using as that's not the goal - it'll certainly be much hotter than the tyres.
     
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  7. elgagon

    elgagon Registered

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    IIRC they never showed the values because the teams refused.
     
  8. davehenrie

    davehenrie Registered

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    The tool shown on the road car at VIR would be very valuable for sims. @Coutie, can such a hud display be built for rF2?
     
  9. Coutie

    Coutie Moderator Staff Member

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    Anything is possible, but it probably won't happen due to lack of time. There's already the real time tire display, can't remember exactly what it shows though, I think it does show temperature.
     
  10. Lazza

    Lazza Registered

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    Toggles between temperature and contact pressure, yep.
     

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