I did some tests today, in my real car.
It was wet, and I do have a fwd. Fairly wide, sticky tires. And all tests are done by feel. That means I did not actually measure any forces on the wheel. But I did concentrate on the forces, trying to exclude my seat-of-the-pants input.
Anyways:
Going straight, I had the normal centering forces, as well as doing a constant radius turn. The force required to keep the turn was increasing slightly as the radius got smaller.
Accelerating, I got a little bit of torque steer, and violent bucking if I got a little wheelspin. If I had a lot of wheelspin, the wheel went very light, and I lost all steering. These are all effects easily seen in LFS.
going straight, pressing the clutch so I was coasting, and the turning the wheel a fair amount resulted in the wheel getting harder and harder to turn, as per the constant radius turn, but at the point where wheelslip started to occur, the force stayed constant. However much more the wheel was turned, the force needed was constant.
During fwd power-on understeer, I got a fair bit of feedback as long as only the inner wheel was slipping (open diff), but once both wheels were slipping I had a very light wheel.
The surprising thing here is the fact that in a wheel-slip situation, the wheel-force was constant. In the beginning I thought the wheel got lighter, but then I started thinking about actual forces vs expected forces. I think the term 'the wheel goes light' is not the actualt fact, but the fact that the force needed increases up to a point, and then stays constant when you expect it to keep increasing.
Disclaimer: It could also be the wet surface, or my power-steering could mask out the effects, but I'm pretty certain my observations are correct under the prevailing conditions.
I'll get the flamesuit ready now, I think.