Car Rear Wings

Contribution from Asdf154:

http://auto.howstuffworks.com/four-wheel-drive1.htm

Explanation from Asdf154:

see the wheel slip animation. without the rear wings, the grip would be less, so the wheels slip. with the wings, it pushes the air up, so got downward force on the car (equal and opposite reaction), so the wheels got better grip, so less wheel slip.