In case you need another data point, I went with 15" wheels because I thought 13" tires were going to get harder to find. I was surprised to see that they aren't much harder to find than 13"! I still think 15" is the way to go if you have the opportunity just because I still believe that 13" tires will eventually become more of a specialty market but in reality, they might become that only a little quicker than 15" tires. The world is moving to bigger and bigger wheels. The 17" wheels on my 2005 MB is looking small now!