Originally Posted by
BobW
Hi Nathan,
The amount of lateral grip a tire can generate is a function of the vertical load on the tire. More vertical load more grip, less vertical load less grip. So by moving the CG forward you increase the load on the front tires which will increase the front grip and reduce the rear. Moving the CG rearward will have the opposite effect. The other thing to consider in the weight transfer is the load difference between the inside and outside tires. The end of the car that has least inside/outside load difference will have the most grip.
I think the bit missing there is that although the tyres with the extra weight have more grip, they will also have more force trying to push them sideways away from the corner. That extra sideways 'push' will be proportional to the weight moved (make one end 10% heavier, it will get 10% more push). But unfortunately the grip gained isn't linear (if you add 10% more weight, you might only get 7% more grip from the tyres at that end). So overall the end of the car you make heavier will lose cornering grip.
This is also why we want the car to be as light as possible; any extra weight takes away overall grip because it's a non-linear return. And why downforce is so wonderful; extra vertical load without any extra weight pushing the car sideways.
This doesn't apply to straight-line braking or acceleration (since there is no lateral load). So moving weight forwards on a FWD or rearwards on a RWD will help straight-line acceleration. For a 4wd you'd want to keep all 4 tyres equally loaded for best straight-line acceleration.