Hi! Ok, I'm not going to add much here, because I'm in the same spot, trying to figure out a very simplistic physics model.

So far, this is what I've done:

• Regular rigidbody box applying addforce and addtorque, tried messing around with frictions, etc. Rotating from the front proved challenging, but overall, it was very hard to have a steering that felt "natural"
• Let go of all of that, and worked with MoveRotation and MovePosition, I got a very decent "bicycle" based model working, the handling worked perfectly, felt very natural, so did the acceleration, breaking and drifting... But now collisions don't work (except with the floor), and it seems pointless to rewrite all collision codes.

I have two new ideas which are:

• combining both, like, using internally a "bicycle model" (check here: http://engineeringdotnet.blogspot.com.ar/2010/04/simple-2d-car-physics-in-games.html) for steering, and then apply the calculations off of those to a torque in the car, to not lose all the collisions.

• Embrace the physics model and use a joint between "front" and "back" of the car, that way steering will feel more natural and drifting will happen... probably friction of the back part will depend on speed and such.

Let me know if any of this helps :)