I have been waffling for the last few days about the wheel selection. I was trying so hard to be environmentally and fiscally correct, but in the end I gave in after running some numbers and getting some more information. Here are my reasons:
1. The 21″ wheels are aesthetically pleasing. Both the wheels themselves and the way they work with the entire car.
2. Tires are actually repurposed when you recycle them! 80% of the recycled tires are used for other purposes. Many recycled items such as plastic do not have a large market and 80% actually end up in the landfill. The reverse case exists for tires. Many are used for fuel and construction products or retreaded. The EPA has a detailed breakdown for 2003 here.
3. I live in the San Francisco Bay Area where we might get some frost less than 10 days a year, so tires that can seriously handle the cold are not important. I also have a 4WD highlander for visiting the mountains.
4. According to my Tesla representative, the Model S tire wear should mimic the Roadster for the 21″ wheel. So in the worst case, my maintenance costs will not go up.
5. Also, the 19″ tire will only last 50% longer than the 21″ tire. I was expecting a very durable tire. With regenerative braking, tires just wear out faster because of the backwards pressure on the tire.
6. The Model S also has a low mode of regenerative braking. This low mode slows down the feature and is very useful while driving uphill on curvy roads. Saves the momentum for the next hill but also saves wear and tear on the tires. The Roadster did not have this option.
7. I do live close to some lovely mountain roads with some very fun driving and hiking trails. Unfortunately they are a bit too busy to justify a performance Model S, but they help justify 21″ wheels.
8. One Roadster owner on the Tesla Motors Club forum reported his Model S tires are wearing much better than his Roadster.
9. Some people are worried about 21″ tires with potholes. If I drove often where there was a lot of potholes, I would consider the replacement costs for the rims. Fortunately, I don’t encounter potholes very frequently.
10. This decision has been haunting me for days. I know I would be happy with the 19″ but I really like the 21″ wheels. I’ve never really taken a fondness to a set of wheels before.
11. I also did a spreadsheet based upon my Roadster tire wear and tear. I replaced my rear tires at 12K and 23K, and the front tires at 21.5K. I think these numbers are higher than average, but I can access a freeway without going through any stop lights. For this same condition, here is the overall breakdown of costs over a 15 year ownership period. I found the exact same tires on some third party sites. The following spreadsheet is just an estimate based upon my driving habits, and predicting the wear on the different sized tires. Your mileage will inevitably differ than this estimate.