I mean, on purpose?

This question is more fun than the airplane on a treadmill question. A few years before Paul Newman passed away (rest in peace Paul, you’re one of my few heroes!), I saw him on a late-night talk show on which he put forth the crazy notion that Formula One cars could drive upside down, since their airfoils provide more than 3.5 G’s of downforce. Build a long tunnel with curved walls he said, take the car to top speed, and you’ll be able to swing up the wall and drive upside-down because of the force created by the car’s aerodynamics. On the surface, it makes sense based on the math, but you’re left feeling that a clever old man is pulling your leg. Searching the web offers what feels like less-than-conclusive answers. WikiAnswers answers pretty confidently, with no explanation. Softpedia tries to offer an authorative answer, but then proceeds to use inaccurate downforce numbers. Even the Official Formula 1 web site mentions the idea, but as a toss-off sentence and no solid math. Personally, I’d love to see this on Mythbusters, especially since even their Mailbag site serves up a gross inaccuracy in which they suggest that drivers experience g-forces because of the aerodynamics of the car. Someone, please help with an answer that provides convincing math! In the meantime, we can still rely on Paul Newman’s sage wisdom. When asked once if he’d like to share any life lessons – the sort of things that had guided him throughout his amazing career – Newman thought for a few seconds before answering with a wry smile: “It’s useless,” he said, “to put the brakes on when you’re upside down.”