Hi, I hope this is an appropriate question to ask here and apologize if not. I'm following your forum posts to the best of my ability using Godot 4. For the most part everything works, however the car is constantly applying z-force in opposite directions, alternating between positive and negative regardless of the actual z-velocity. Is that expected? It causes the car to sway back and forth when idle, and causes the kph reading to fluctuate wildly.
It sounds like everything might be working as expected -- this type of equation for tire forces is undefined when a wheel is at rest, because it is defined by slip/deformation. Under this model, a relaxed tire never really rests; it oscillates between gripping one way and another.
I recommend a minimum physics tick rate of 120Hz to mitigate the inherent error. Shorter intervals are better, at the expense of CPU. Then...hiding/clamping the fidgeting by brute force. The latter is a programmer's art. I owe a devlog to explain how I've addressed that problem, by request.
Sorry it's late, but I wrote about the solution now:
https://lupine-vidya.itch.io/gdsim/devlog/677607/tires-at-rest-a-deceptive-solut...