They very well may be 10 and 13. I'm not positive. But I couldn't see the Chrysler website being incorrect. My old car has 8.5 rears and ours could easily be another 50% wider.

Our rear tires are definately as wide as some I've seen on Porsches and other high end sports cars, so 13 and 10 isn't as crazy as it sounds.

I also think they are a little wider than we actually need for only 215 hp which is another reason it sounds too high.