Skywagon said:
The lightest aftermarket wheels in a similar size are in the 11 lb range; most are around 13-14 lbs. Plus you cannot factor wheel weight as static/dampened weight as it is un-dampened and rotational mass (inertial) as well. Your 140 lb loss estimate is not correct.
Ya, I blew that simple math!
I disagree about factoring in wheel weight. Whatever weight is attached to the vehicle must be propelled up a hill. If it doesn't matter, as you say, then a simple test is to fill the wheels with calcium and then measure the performance. I predict a profound change for the worse in every measure.
My top speed up a local hill near my house was noticeably slower (82mph) than level (95 mph). Hopefully, that makes sense. Whether I add four 300 pound lead wheels or 1200 pounds of lead on the roof, both will have a measurable decrease in max speed up that hill.