I used Truss Physics for the tires: http://forum.unity3d.com/threads/released-truss-physics-for-unity3d-soft-body-simulation-plugin.349503/
I also used Truss Physics for the leaf springs and for the airbags and the rear leaf springs.
I am trying to make a physics based logging truck.
My System Specs:
- CPU: Intel Core i7-4790K Processor 4 GHz
- Graphics Card: GIGABYTE GeForce GTX 970 OC WindForce 3X
- RAM: 12GB RAM
- Operating System: Windows 7 Ultimate 64-bit