So the weight of where the tire mounts to the rim does not factor in at all? I have an experiment planned out this weekend, should imitate what forces the vehicle (axle) sees under load.

You're using the 17" & 18" as the radius...my point was using the wheel & tire combination as the total radius/diameter.

A 235/50-17 will have a longer radius than a 225/35-19. Now factor in a lighter wheel/tire combo on the 19 and you will accomplish a 19" wheel/tire combo with less rotational mass. Right?

You'll also have a better (stiffer) sidewall on 35 series compared to the 50 series. Better handling, but ride comfort will be diminished.

I don't want to get off topic in the braking thread so I'll post this here....

Lets say the given VQ makes 250 Ft/lbs (easier math).

Using I = MR^2 and tau = I*alpha

the 18" and 17" wheels will weigh 20lbs for the exp.

The 18" wheel is .15 alpha while the 17" will be accelerating at .17 alpha or to put it in a more relatable perspective...

To accelerate a 18" wheel as much as a 17" wheel (at 20lbs a wheel) it will take 35 more ft/lbs!!!