I put winter tires on my P85 a few days ago, replacing my stock 19" Michelin Primacy tires with Pirelli Sottozero 3. Took it up to Tahoe and it did fine with a bit of ice and snow and the road but nothing too challenging. It also did fine around home and during long distance travel. Almost as quiet as the Primacy tires. I think my energy efficiency has dropped a bit, but I'm not really sure yet. The handling seems fine, but I haven't done anything to push it. There were a couple of problems with getting winter tires from Tesla: winter wheels/tires on the Tesla store were out of stock no appointment at a service center here in the Bay Area could be had any time soon I didn't like the winter tires Tesla chose So I went third party. I ordered a set of Pirelli Sottozero 3 tires (245/45R19 102V XL) from Tire Rack (~$1100 with shipping). Why those? Most of my driving will be around home in the Bay Area or on the road to Tahoe and back, so I wanted a tire that would perform well when not in winter conditions -- a compromise. I figured Tesla had made the trade-offs and probably got it about right with their choice of the Pirelli Sottozero. My only issue was that it looked from Tire Rack reviews like the newer 3's were just better than than Series II. I had them shipped to Tires Unlimited in West San Jose, one of Tire Rack's premier installers and highly rated on Yelp. Their price for for swapping the new tires in was $60, which was way cheaper than some other choices I checked on. They did a fine job, quick and courteous, and put my old tires in bags in the back of my car. Tire Rack mailed me my receipt and a rebate form good for $60. I know of no technical reason for having winter tires on a separate set of wheels. So far as I understand it's just an issue of expense in swapping the tires twice a year (and possibly convenience if you like to do the swap yourself). If that $60 price holds it will be many years before the cost of swapping gets anywhere close to the cost of a new (or even used) set of wheels and TPMS sensors. So I think I'll stick with the one set of wheels for now. Hope this is helpful for people trying to figure out how to deal with the winter tire issue.