Wheels falling through the ground

So I made a car. It has wheel colliders and everything s in the parent of the Chassis. The Chassis has a box collider and a rigidbody. When I press start the wheels glitch out and the back ones move up to the left, and the front ones move down to the right. Then they fall through the ground but the wheel colliders stay in place, then fall through the graound. the car then falls onto the ground like there were never wheels. Help?? (Unity 5)

Add a Collider to the vehicle, even if it’s just a box collider.

A car without standard colliders results in the rigibdody having an identity inertia tensor (1,1,1). This causes strong instabilities when the wheel colliders try to keep the vehicle stable by applying the suspension forces. These instabilities is what you are watching in your case.

Use EasySuspension for best stable setup for wheel colliders: