Can anyone tell me the way to figure out rotational inertia. Let me clarify what I am asking. I learned that because of rotational inertia, reducing the weight of a wheel for instance by 1 pound, equates to a reduction in the "perceived" weight the car "feels" by much more than 1 pound because of the concept of rotational inertia. I also know that the diameter of a wheel plays into this as well. I am contemplating changing the wheels on my S80 T6 and want to be able to calculate how much of a difference a reduction or addition in weight, and an enlargement in diameter would make. Any help would be appreciated.