I would like some input on the pros and cons of the 21 inch tires and wheels vs the 19's. I have not driven the model s with 21's except when I did my original test drive in January. I was so excited at that time did not really pay attention to the ride. When I configured my car I went with the practical knowing the problems with curb rash and tire wear. But I really like the way the 21's fill the wheel well, and still have this little bird in my head saying who cares about practicality go with you gut. So any input on the noise, ride quality, mileage issues tire wear would be appreciated.
I could not justify getting the 21s. It was a simple matter of performance + looks vs practicality + cost of maintenance. When I ordered, the 21s were "free" with a P85, and I chose to "downgrade" to the 19s. And now the 21s are a $4500 option, so one way of looking at that is that I "gave up" $4500. You may now ask "why?" and I will explain....
Normal Treadlife
First and foremost, I am a high mileage driver. Currently about 50-60k a year.
Let's assume that alignment is perfect for the time being and stays perfect. (I'll get back to this later). With 21" high performance summer tires, you
should be able to get 15k miles per set. With the 19" Goodyears (assuming the same with the Michelin MXM4s), you
should be able to get 50-60k miles per set. (I am currently at 34k miles on my original OEM goodyears, and I have about 20k treadwear life left).
Based on that, it's simple math to calculate that I'd need about 4 sets of 21s per 60,000 miles vs 1 set of 19s per 60,000 miles. Cost of maintenance.
Weather
Second, those 21" tires will not handle very well in adverse weather conditions. They are summer tires only. They won't grip as well in rain and especially snow. So safety is a big factor in my decision too.
Structural Integrity (aka hitting potholes, curbs, etc)
Third, the "low-profile" (aka height of sidewall) are so thin on the 21s, that hitting a decent size pothole at a decent speed will likely cause a blowout. Many owners (such as one a few replies up) have experienced this. The Model S does not have a spare. So this means getting towed. If the pothole or object was big enough, it's very likely you also bent or cracked the rim, and now the cost of replacement for one tire + rim is getting upwards of $2k.
P85+
IF you have the P85+, those tires are about $600 each, and having them replaced by Tesla themselves (not some local shop) is about $1k per tire. No thanks!
Alignment
A big ongoing issue right now (let me repeat, a HUUUUUUUGGEEEEE issue) Tesla is having is they are having some alignment problems right now and the 21s mounted on the rear seem to be burning through the inside shoulders down to the cords in 5k miles. There are one or more factors at play here. I am not going to detail thsi here, but if you search these forums you'll see many threads regarding this. What it comes down to is that many owners have needed to replace their 21s every 5k miles. That is very expensive. There is not really an "official fix" aka TSB for this yet, but we do know there needed to be some adjustments to the alignment machiens and new adjustable camber bolts distributed to help allieviat this issue.
Curb Rash
Well, this should be obvious but big wheels + low profile tires means if you're not careful, curb rash is a bitch.
Other
Well it's not really looking good for the 21s now, is it ? They are also "louder" (road noise), & "harsher" (you feel the bumps in the road a lot more), range is also not as good as the 19s, BUT on the more positive side they look nicer..... I would say they handle/perform better, but you could just put 19" summer tires on and get the same effect so that's not really specific to the 21s.
Good luck with your decision.
(FWIW, if money was not a factor, and if I don't mind getting towed every time I hit a big pothole, I probably would have kept the 21s).