This uses a mixture of raycasts and adding gravity values to the car and then setting the gravity value when the car hits the ground, which also makes the car stick to the ground, and no you cannot smash through walls.
https://www.roblox.com/games/6684885049/Car-Physics-Testing
Bugs:
Being able to move during chat (fixed)
No de-acceleration when stopping (fixed)
This is pretty nice I like it. 
Pretty nice.
I’m not too familiar with custom gravity so is there meant to be another car following it or is that just an issue?
Did you check out my topic in building support then come up with this?
For real, I was looking for something like this, but, the question is, can it drive upside down?
No. I can make it do that though.
That’s the server car of which I have not hidden from the client yet.
