[mcrews]

I'm not a math guy but here is my thought pattern...or random thought forced together!!!

there is static wieght which is the car at rest. 2400 including tires
when the car moves, the the weight of the wheel is compounded because it is rolling
the stock car is designed for that so that is the base line

The new combo is 12lbs heavier. Given your design, probably 90% of the added weight is at the uotside edge of the diameter. There is a formula that says adding mass on the end increase the moving weight 3-4 times (someone posted on wnother post)
Sitting still the new weight is 2400+(12x4 tires)
When the care rolls, the static weight of the car is the same 2400, but the spinning weight at the end is 3-4 times greater 2400 + 4(12x4)

Thats why tire weight is really so important.
uotside of trucks(whole different concersation) cars with +2 sets ups tend to eat thru brake and suspension parts.

Now, I realize you drive easy, but moving spinning mass is spinning mass.
sorr I don't have specific formulas but they have posted by others.