I just returned from Tesla Service, who had my car for 3 days. We were doing sunroof stuff and a few campaigns. I was given a brand new (250 m) P85 with 21" and Continentals to use in the interim. I just changed the wheels and tires on my standard 85 to these:
The rims are TSW 19" x 8", essentially stock size and the tires are 245x45-19 Michelin Pilot A/S 3. I now have about 700 miles on the set and I had 5300 miles on my Goodyears. The wear on the stock tires was perfectly even (i did rotate quite often at first) and assuming 3/32" tread left, my project mileage would have been 25,000 miles. BTW, I am planning to sell the stock rims and tires if I can find a buyer.
The timing of all of this worked out so that I have been able to compare 3 different tire/wheel combinations in a relatively short time frame. I found my stock 19" to be loose and twitchy at speed. The car wiggled all over the place on a grooved road. The ride is nice and the noise level on the Goodyears, once rotated a few times, is admirably low. Driving the new P85 with standard suspension (air like mine) I found the 21" Continentals to ride softer! I was really surprised by this. They are similarly quiet. The Goodyears and Continentals make different kinds of tread noise, but nothing very loud or noticeable. The highway stability of the Conti's is much improved over the Goodyears and the steering response is incrementally faster. The 21's seem to use a bit more energy around town but drop down to the same or even better at highway speeds. I can only guess this due to the added rotational energy required to spin the 21's which becomes less of a deal at constant high speed. Based on this, if I had it to do again, I would probably get the 21's with the Continentals if you want to stay stock and have the smoothest and softest ride along with better handling. Basically the Goodyears aren't very good.
My new rims are 21 pounds vs 30 for the stock 19". So my new wheel/tire combo reduces the total weight per wheel by 8 pounds! The new Michelins are technically All Season tires as they are alleged to have terrific performance in wet conditions. This is of no particular importance to a Southern California boy like me. I stayed with "All Season" because I didn't want to take the energy hit of going from an A/S to a full on dry tire. There are only a few reports about this tire so far and they all claim performance tire behavior in an A/S package. Well this claim is completely true. The Michelins completely stomp the 21" Continentals in handling and most particularly in turn-in behavior. It feels like I changed the steering ratio on the car. These things are really quick and precise. All of the wander and instability at speed went away. They have a very high tread wear number of 500. I don't have enough miles on them to make a projection of wear yet. So the good news is that these things simply transform the Tesla into a cornering beast. They ride very nicely especially considering that I dropped so much weigh in the rim. They are a little sharper over tar strips, but I'll bet that on the stock rims that wouldn't be the case. Unfortunately, they are a bit noisy. They make a whirring or whining sound, primarily on concrete roads, mostly between 60 mph and about 75 mph. With the radio on, it is masked, but they are definitely noisier than either the Goodyears or Continentals. So far (about 700 miles) I have seen my average consumption go from 312 to 324, or about 3%. It has gotten much hotter here over the last month so I'm not convinced it is all due to the tire.
I am here to tell you that the 19" rims with appropriate tires can easily equal or exceed the performance of the 21" rims with similar tires. This conclusion was also reached by one of the car magazines a number of years ago when they tested rim sizes against each other. Actually I think 15" or 16" actually won. I don't personally care for the appearance of the 21" wheels and that coupled with my fear of a 35 series wheel/tire combo breaking on pot-holes, I went with the 19's. I guess Tesla now offers the Michelin Primacy tire on the 19's. I'm sure it is better than the Goodyears. Tesla will now supply the Michelin Pilot Sport on the 21's. That tire is several levels beyond mine but it is also noisy, somewhat hard riding and really short lived.