This is a paid asset, but now you can download Wheel Controller 3D Free.
Detail this asset from Unity Store: Original Link
Wheel Controller 3D v4.1.0
Wheel Controller 3D v3.4
If you are looking for a complete vehicle physics package with WC3D included, check out NWH Vehicle Physics.
Wheel Controller 3D is a complete alternative to the Unity’s inbuilt wheel collider. It allows for more realistic vehicle behavior, complete customization and 3D ground detection. No more “stick” wheels.
• Wheel has width and length, not only a single point in the middle.
• API with almost no differences from Unity’s inbuilt WheelCollider – familiar and easily swappable.
• Fully customizable via custom inspector. Adjust spring, damper, friction curves, geometry, etc.
• Adjustable camber, caster and rim offset.
• Pacejka friction model with support for different surfaces.
• Friction preset system that uses ScriptableObjects for easy setup.
• Adjustable at runtime.
• Adjustable ground detection resolution with multi-threading for very low performance impact (Unity 2018.2 and newer required).
• Can handle wheel visuals by itself (rotation and position).
• Suitable for different kinds of vehicles: cars, trucks, motorcycles, tanks, etc.
• Easy to set up.
• 0.03 ms of CPU time per frame for an average wheel.
• Full C# source code included.