It´s all fake it´s a computer sim. I don´t know how you fake fake the tire modelling
.
I'll use an analogy of Aerodynamics because I know more about it
If you are designing a flight simulator of a particular aircraft, you need to know how the wing reacts. The physics involved is incredibly complicated. You could just go out, find the plane, put a few sensors on it and measure what's happening, then put those numbers into your game and interpolate for values that you dont know (ie. guess for values you dont know).
The other alternative is trying to do realistic aerodynamic modelling. Basically meaning you have to solve the Navier Stokes equations millions of times, huge arrays of matricies of partial differential equations. To run the simulations in real time would take computing power beyond anything available to consumers and possibly even more powerful than the massive government owned supercomputers (it takes hours on the super computers at my university just to run "snapshots" in time of a simple wing). To run them accurately you'd need an incredible understanding of not only the aerodynamics but also the structure which will vary because of the pressure forces on it, which will in turn affect the aerodynamics. Then that too has to be modelled. At the end of the day, you've spent billions of dollars in research, got something that requires God-like computing power, and at the end of the day probably has massive inaccuracies because of some assumption you made (or you told the computer to make) to make the equations remotely solvable.
All when you could have taken option 1 and just "faked" it with numbers off one of the real aircraft
The tire physics are the same. The cornering force essentially comes from your slip angle, camber thrust and elasticity. Those things are dependant on temperature, side wall height and thickness, pressures, compound, how the compound varies through the tire, which again is dependant on temperature and pressures, etc etc etc, I doubt most race engineers could tell you everything that goes into it. At the end of the day, why not just take a car, put a few sensors on it, and take it round a track and then put those numbers into the game. Forget trying to accurately model the tires, just fake it