Does anyone have figured the WheelFrictionCurve struct ?

I've read the doc about the WheelFrictionCurve struct. I think i've got the stiffness property, but i'm kind of lost on the 2 points of the spline Extremum and Asymptote. How exactly they affect the Physics. In my project, using the default values, when i accelerate, the car tries to rotate forwards. I thought it was too much friction on the front wheels then i turned down the stiffness of them a bit. So far, so good, but when i try to steer, it overturns.

Any help is appreciated.

Thanks in advance.

My experience is, this: trial and error, there's is not much realism in the whole wheelcollider stuff, but as long as you happy with arcade feel you can get good results. Note that you have to set forward and sideways curves separately. 3DNemo made a little online tool to experiment real-time with the different parameters, you can find it here.

It's based on the Placejka Tire Model. Here's some advanced information:

Basically, the curve represents the friction generated off the point based on the relative speed of the wheel against the ground.