Wheels don't work upside down

I made a car with wheels big enough that it can theoretically drive upside down, but it doesn't work properly, the wheels just float. I know this is really dumb, but it would be nice if it worked, if that's even technically feasible

 

Probably just something wrong with your tires

 

That's strange, any idea what it could be?

Edit: guess it must be something with automation, but I really don't know what