I just received my new Arachnid's yesterday. Since I got to use the Tesla Mobile Service, I was able to weigh the old and new tires/rims myself:
Original tires/rims: 19" rims, Goodyear Eagle Touring M+S 245/45R19 98W, (55.2 lbs ea * 4 =
220.8 lbs total)
New tires/rims: 21" rims, Michelin Pilot Super Sport
Front - 245/35 ZR21 (54.0 lbs * 2 = 108.0 lbs)
Rear - 265/35 ZR21 (57.4 lbs * 2 = 114.8 lbs)
Total weight = 222.8 lbs, for net gain of 2 lbs.
I was bummed, as I was hoping for moderate weight reduction due to some other post mentioning saving of 7-10lbs/wheel!