Unity3d wheelcollider falling through terrain

Question

I have created simple project with 3D car and terrain. I have added 4 Wheel Colliders on model wheels. But when I run project wheels falling through terrain.

Before run:

After run:

I am sure that at start wheel colliders above the terrain and not intersect it. Configuration is:

In what problem is? I have tried a lot of different things but I can't find a solution.

Answer 1

Do "not rotate" the WheelCollider components. WheelColliders are implemented as ray casted down, you can see the direction of the ray on selecting the same in the editor. To get more accuracy try tweaking Physics.minPenetrationForPenalty and Time.fixedTimeStep.

Edit: Noticed the rotation in your inspector window.

Answer 2

I had a similar issue, on a model imported from Blender. Blender uses a different axis than Unity, so the imported model had an x-rotation of -90 degrees and the wheel collider ray-casts forwards, instead of downwards.

To fix it, in Blender:

In object mode, set the X rotation of your model to -90. Press Ctrl + A and apply rotation, X rotation appears to be 0 now in Blender, set it to 90 and save/export it. You'll see that it will appear both correct and at 0 rotations now.
_{- Unity Answers: Rotation when importing from Blender}