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I had loaded up a theoretical model of the MR2 at stock 91 ride height, but based off the tire setup on my car, which is 245/40-17 rear, 225/45-16 front. I was looking at the roll center heights, and found that the front was about 2.6" off the ground and the rear was about 3.6" off the ground. I then got to thinking, what if the higher rear roll center is caused by the taller rear tire. I remodeled it for a rear tire with a 1" smaller diameter, dropping the entire car .5" in the rear. This lowered the rear roll center by LESS THAN .1".

So the CG dropped by a half an inch, but the roll center only dropped by a tenth. Remember, if you bring your CG and your roll center closer together you reduce body roll. At first I was baffled by this, but then I remembered that part of the calculation of roll centers involves the tires contact patch. If you bring the contact patch closer to the CG without changing the suspension geometry you bring the roll center and the CG closer together.

Now, practically applying this may be difficult, since its tough to upgrade tires on our cars without increasing diameter (due to limited selections), but its something to keep consider.