It would seem like having a bunch of wheels pre-painted for all the different sizes and colors available would take up a bunch of floor space + you would need someone to keep track of the quantity in advance so you have enough to match up with the cars being built. I bet they just grabbed them as needed and tossed them in the paint booth along with the car and then they were pulled out, had tires mounted, and then drug down the line where they were eventually installed on the car. Just guessing on my part.........