Most "interesting" Unity car physics projects move away from the standard WheelCollider in favor of more stable, custom solutions:
: Ideal for realism seekers. This project replaces standard Unity wheels with a custom implementation using the Pacejka tire model for more accurate longitudinal and lateral forces. Simple Raycast Vehicle car physics unity github
If you are starting a driving game today, do not write a car controller from scratch. Clone a GitHub repo, drive it for five minutes, and then open the code. You will learn more about torque, drag, and friction than any tutorial could teach. Most "interesting" Unity car physics projects move away
Instead of using physical wheel meshes as colliders, cast a ray downwards from the car's body to detect the ground. Use to calculate the upward suspension force: drive it for five minutes