I realized that the instability and jittery behaviour of the cars when stationary or when in motion seems to be due to the overly exaggerated tyre pressures. It would be nice to see some form of tyre physics be implemented so that tyres can flex under load/pressure.
Tyre pressures are realistic. The vibration you're seeing is due to the tyres not being perfectly round, a product of them being polygonal. Perfect circles are not possible with polygons, and making tyres/wheels with stupid amounts of polygons will only slow the game down with little advantage.
The pressure isn't overly exaggerated. It is using real-world PSI values. There is just some inherent instability in node/beam tires.
Oops I'm sorry for the criticism. It just seems to me the car bodies are extremely unstable and wobbly right now, causing vehicles to bounce around much more than they would in real life. I hope this is fixed soon in upcoming builds so that the maps with bumpier roads are more drivable.
Re: Lower tire pressure Outside of North America, tire is spelled "tyre." Its similar to how Americans spell color instead "colour". Check instead of "cheque" etc
Re: Lower tire pressure I think he was more referring to the fact that he spelled it "Tire" in the post. But @ OP, you can modify the tire pressures in the vehicles folder, I forget the exact files to modify, but I'm sure someone can say what.
The problem isn't the cars or the physics, it's the bumps. The bumps are massive, probably much bigger than any potholes you'd find in real roads, which is being addressed.