Doors. If we were talking about total made then maybe wheels. But it's more common that a wheel would be destroyed than a door when the wheels buckle, or the car is destroyed. Doors get replaced too but not as often.
Plus you have the doors on the car/truck, plus the doors on every house, apartment, garage, toilet, building, tenancy, every fire door in every building, etc. In a stand commercial building on each level you'll have fire doors, riser doors (comms and electrical), doors for tenancies, etc.
Then comes the killer. Walk up to your wardrobe and open the wardrobe door. Walk into the kitchen and open every single cabinet door.
Doors.
Side note, if you don't specify specifically vehicle only, I'm going to work with what I have.
