Originally Posted by Dave-ROR
It has a great effect on the car when say, braking from 100mph down to 60mph when entering a corner.
The more over 100 you go, the more you need the wing.
Even with the wing, some people have a hard time slowing from 135-145 in a hurry to make a turn at the end of a straight. There can be a brief moment that the car feels like the rear's trying to go faster than the front, and every teeny movement of the steering wheel is greatly exaggerated because of the force coming down on the front wheels.
Jason Franza, Honda Challenge champ in '03, is a good person to ask about this.
When he was coming along in the NASA driving programme, he took his wing off as an experiment, and promptly put it back as quickly as possible.