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Elliptical grip model

105k hpgbproductions  5 months ago
Version 1.2 Tool


This mod modifies the default grip model used by the resizable wheel, hereby referred to as the "rectangular" grip model, with an "elliptical" grip model based on simcade games to better resemble real tires.

The unique handling styles of each drivetrain type come from the "circle of forces" - as longitudinal slip approaches the limit, lateral grip is reduced. Differences in traction between the front and rear wheels will produce different behaviors on different cars. However, the vanilla rectangular grip model does not have have this relationship between lateral and longitudinal grip, and therefore, most special features of each drivetrain type are lost.

The mod aims to restore those effects by setting grip multipliers in the direction perpendicular to grip demand. The slip extremum and asymptote values are used to create one ellipse each for slip extremum and asymptote. If the slip remains within the extremum ellipse, the wheel is considered to be under normal loads and there is no grip reduction along either axis. However, as the wheel exceeds the extremum ellipse and approaches the asymptote ellipse, it is considered to be overloaded, and grip is reduced in the direction perpendicular to slip.

In addition, tire smoke and skid marks are added based on how much the tire is overloaded.

The following Desmos graphs are used for prototyping. Some equations are provided but may differ from those used in the mod.


The following mods are used in thumbnails:


  • Tested in
  • Satisfactory results can only be obtained if a car is reasonably realistic and tuned for this mod.
  • The mod has no effect if none of the wheels has a slip that exceeds the extremum zone, i.e., the handling must be limited by grip.
  • The mod has no effect on landing gear parts that are not using resizable wheels.
  • The script checks for new resizable wheels every 10 seconds. It will take a moment for newly spawned AI aircraft to be affected.
  • Particles use the existing particle system on wheels, which in the vanilla game, only activated during a hard landing.
  • Skid marks may not support irregular combinations of rotation and scale of resizable wheels.
  • Settings data is saved under NACHSAVE\EGS.DAT. The file is created after restarting or quitting a level for the first time. Settings can be reset to default by deleting this file.
  • Does not use real-life physics data.


Displays grip multipliers and wheel slip for all resizable wheels in the scene.

Turn on or off the emission of particles. Previously emitted particles are not removed.

Turn on or off skid mark generation. Previously generated marks are not removed.

The wheel overloading factor is raised to this exponent to get the opacity of particles. Increasing this will reduce smoke density at low overloading factors. Default: 3

EllipseGrip_SetParticleColor (color c)
Set a tire smoke color. Default: 1,1,1,1

EllipseGrip_SetStrength (float strength)
Set the maximum loss of traction perpendicular to slip. Default: 0.25


Notice: Example cars are tuned for the mod. They will drive differently (maybe badly) without the mod.

RWD car with rubber more suitable for erasers than sports cars. In MT mode, gear 4 and above will largely prevent any wheelspin.
You can also try the extremely simple traction control by activating it in the variable setters menu. (It just cuts power when wheelspin exceeds the extremum value)
Like the original car, you can use AG3 for linear steering mode. With a steering wheel and a lot of skill, it should be possible to recover from spins. It is largely impossible to recover from spins in steering assist mode as the steering angles are too small.

Added a simple limited-slip differential that outputs a correction torque proportional to the angular velocity difference of the rear wheels. It prevents the free-spin of a single rear wheel, which can happen due to bumps or cornering.
In addition, a counter-steering assist factor has been added to the steering assist mode, but its performance is poor.

MRC FLEX-V EGS-2a (Assist Prototype)
Added TCS on Activate4. If there is excessive longitudinal slip in the direction of motion, the engine input will oppose it. Sensitivity is proportional to gear ratio.
Added ABS on Activate5. If there is excessive longitudinal slip against the direction of motion, the engine input will oppose it. (This does not mean that the brake torque can be set high! You should still use a brake torque close to or less than the amount required to lock the wheels.)
Changed grip curve so it falls off more gently after the extremum point.
There is a bug that affects edge cases of throttle and brake combinations. This will cause the car to stop before continuing.

Second re-tune of the funny car. It is possible to change the drivetrain without touching any FT, but two tires cannot handle the power.


1.2 (2312272020)

  • The settings that can be changed using commands are now saved when exiting or restarting levels.

1.1 (2310142330)

  • Added skid mark visual effect using UnitySkidmarks by Nition
  • Added tire smoke exponent to reduce smoke density at low tire overload levels
  • Fixed incorrect behavior of SetParticleColor command

1.0 (2309232130)

  • Initial release


  • When a tire leaves the ground, smoke continues to be emitted. Unfortunately, the IsGrounded property of resizable wheels does not work as expected, so I cannot use it for this purpose.

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  • Profile image

    @001 :xpp: :ElNoSabe:
    But seriously, programming has this stuff called dependencies, where you rely on others' code. Some company made some changes and along the way you lose mobile mods

    +1 28 days ago
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    26.6k 001

    @hpgbproductions, why there's no mobile version?

    28 days ago
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    125k BaconEggs

    @hpgbproductions oh ok thanks I dint read too far into the changelog

    2 months ago
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    @BaconEggs ok, settings that can be changed using commands are now saved between runs. It doesn't use the mod settings mod

    2 months ago
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    125k BaconEggs

    u should make a mod settings menu that allows disabling of particles & skid marks that stuff does actually nothing and it is so annoying to disable every time i load in

    2 months ago
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    @rexzion me too

    3 months ago
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    41.0k rexzion

    i love it when tire marks in the air

    3 months ago
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    Love the MR2 AW11 in the thumbnail, a grippy car for this mod. Have an 88 SC myself that I rally.

    +3 5 months ago
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    63.9k Juanfly154

    Dude this is awesome. Please do more mods !

    5 months ago
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    230 kman1

    @ShinyGemsBro thanks, my tiny brain cant comprehend any thing, my computing rate is 2kb per second!

    5 months ago
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    @Freerider2142 oh so it means we can drift now

    5 months ago
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    15.1k Johnnyynf

    This makes the grip so so much better, I'm addicted to driving in SP again.
    I know ur not a magician, but could you maybe take a look at this problem too?
    I'd believe it's due to the fact that when the grip doesn't scale properlly with the positive force (aspecially when the wheel get light). That setting probally do exsist because down force works with cars.
    If not multiply the grip by the how much build-in suspension is compressed would probablly work too.

    And also if you can, some how give wheels brake FT input option.

    Ur doing great work my man

    +1 5 months ago
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    @ShinyGemsBro drift, sure, but to drift properly you probably want to add funky trees

    5 months ago
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    @StockPlanesRemastered you don't need to know all that to use this mod. Like with the vanilla tire model, just set traction until it feels right

    5 months ago
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    31.0k ShinyGemsBro

    For the kids at home, this mod simply allows you to drift properly.

    5 months ago
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    Congratulations on 100K!!!

    5 months ago
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    In Other words if you run this mod you need some sort of actual spring based suspension (either leave, double wishbone, or double coil over, and you need to know how camber, tow, and caster work.

    +2 5 months ago
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    Am confused

    5 months ago
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    This is the Game update I've been wishing for 2-3 years now.
    TY for this!!

    5 months ago
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    this should be in the actual game tbh.

    +5 5 months ago
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    ok, just tried it out, awesome, I was already doing a lot of laps on the Nordschleife with a really great car with awesome physics, but this really does a lot.

    5 months ago
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    @Nerfaddict somewhat yeah. If the asymptote is too close to the extremum, the wheel will lose grip too quickly. Usually street tires lose grip slowly compared to racing tires.

    5 months ago
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    @Heneepr it cannot detect the weight on the wheel as there is no built-in functionality for that to begin with. (also see comment below)

    5 months ago
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    @FlyingPatriot i can only make adjustments to the ResizableWheelCollider component, which itself is based on the WheelCollider component. That feature needs a completely new wheel part

    5 months ago
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    28.5k Nerfaddict

    So if I set the asymptote as high as humanly possible, the tyres will take basically forever to lose grip?

    5 months ago
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