Ordered my new '12 MCS wheels with the R121 wheels. I'm thinking of going with all-seasons and wanted to know if I should go with the 205/45/17 or 215/45/17 tires. I'm pretty sure the R121s are 7". Any suggestions? What looks better? What about handing, MPG, etc.?

 

Those sizes are so close that you might not be able to feel any performance differences. The 215 is a little wider, but is also a little taller and heavier.

Specifically, the 215 is about 10 mm wider, and about 8 mm (.3") larger in diameter, so should weigh about 1 pound more than the 205. Theoretically, the 215s should provide a little more contact patch (and a little more rolling resistance), a little softer ride, a little less cornering sharpness at turn-in, a little more fuel consumption, a little slower acceleration (and less braking efficiency), and a little less speedometer over-read (by about 1 mph) than the 205s.

All of these differences are very small, but the aggregate of small differences might yield an actual difference you could feel. I don't know, so I'd better yield the floor to someone who's tried both sizes in the same tire.

 

My clubby came from factory with 205 run flats. I switched to 215 non runflat last summer. More grip. More comfort. Less pricy (more tire choices in the 215 size). Steering feel is pretty much the same. And an added benefit is the 5% speedo off speed is corrected a little :-)