Its the aerodynamic center i believe
Yes, I know the teams work heavily with the aerodynamic center of pressure in relation to the center of gravity. Because the aerodynamic center is constantly changing in magnitude and location (due to the pitching and rolling motions of the chassis), and the CoG is not changing nearly as much (a little during roll and bouncing off curbs), there must be a constantly changing 'moment' (leverage) caused by aerodynamic center. I'm not sure what they call this moment or truly what it's affects are, but anytime forces are not in line with each other, a moment is created.
Obviously, this means you would want to have the center of pressure between the wheelbase, or otherwise the car would be very unstable at speed.
I'm not certain on this, but when we have seen cars flip (example: Mark Webber at LeMans99) it is usually because they caught the air at a certain angle. I'm wondering if this relates the center of pressure to moving off from between the wheelbase of the car, or if it just reversed the direction of the center of pressure (i.e. worked to make pure lift instead of downforce).
They did tell him not to follow cars too closely and they added front downforce which would suggest that the center of pressure was moving rearward.
However, Mark Webber's #4 became airborne at the Indianapolis corner during Thursday night qualifying session. The car was rebuilt from scratch on Friday, modified for more downforce at the front, and entered in the Saturday morning warm-up. This time, Mark Webber only made it to the Mulsanne kink when the car back-flipped in a spectacular way, this time caught in mid-air on photos. Luckily, neither Webber nor others were injured on either occasion.
Despite the second incident and the awareness of the 1955 Mercedes Le Mans diaster Norbert Haug decided to go ahead and enter the other two cars in the afternoon, with additional modifications and instructions to the drivers not to follow others cars closely over humps.
I love to love Senna.