force needed to turn bigger tires/wheels calculations

[mysticclam]

Ok, this is really ballpark right now, i made assumptions about weight distribution. I beleive the formulas I was using assume all the weight is at the end of the radius (what would be the outer edge of the tire i mean) But I got these numbers for increased force needed to rotate a larger tire (just the tire not doing anything with rims - yet)
Do these sound reasonable? It would seem to match peoples MPG changes

(vs stock 235)
31x10.5 38% more
33x9.5 58% more
33.10.5 72% more

Im trying to get some actually weights for the same model tire in these 3 sizes and then Im hoping I can approximate the total force needed to accellerate to 60 MPH and see what % of the total energy used is just to spin tires.
The usefulness of this is I may be able to make a calculator that will estimate MPG and 0-60 time changes for a given wheel/tire choice. (I guess that would assume gearing was compensated for)

 

[mysticclam]

Got this information from BFG today. Im really surprised. It destroys my numbers. I will get the weight of a factory tire and recalculate it vs these numbers. Also from these numbers, a square inch of contact area is much heavier than an square inch of sidewall, at least on the BFG AT
In fact, i could extrapolate the ratio and guestimate other tire sizes
BFGoodrich All-Terrain T/A KO tires:


LT235/75R15: 35.32 pounds
31X10.50R15 = 40.40 pounds
32X11.5R15: 45.47 pounds
33X10.50R15 = 44.67 pounds
33X9.50R15 = 40.11 pounds

Using my formulas, this would make the skinny 33 only 6% harder to turn than the wider 31. Im really surprised it weighs less.

Added stock size and 32x11.5 from BFG