Pacejka data integrity at high Fz

[LBodnar]

Code:

btVector3 CARTIRE::GetForce(...)
{
...
    if (Fz > 30) Fz = 30;

This might be very optimistic. Magic formula limits are smaller and data will start to break up at lower loads, typically 10kN or so. First usually goes Mz by first becoming a straight line and then just flipping over.

These sort of loads might be triggered by road bumps, etc. I suggest limiting the range fed into Fx, Fy, Mz formulas and scale the outputs to keep them sane but still proportional to tyre load e.g.

Code:

    btScalar ForcesScale = 1.0;
    if (Fz > 10.0)
    {
        ForcesScale = Fz / 10.0;
        Fz = 10.0;        // set Fz top limit.  Pacejka formulas break up at high Fz
    }

...
    return btVector3(ForcesScale * Fx, ForcesScale * Fy, ForcesScale * Mz);
}