I have Dunlop 205/40-18s on my JCW and have no problem with the ride or handling. However, I am going to need to switch to all-season tires. There are no runflats available in that size. I am thinking of changing to Michelin AS3s in either 205/40-18 or 215/40-18. My car is my daily driver and I drive it on long trips including sometimes experiencing some cold weather( colder than recommended for summer tires). If I buy 215s will I notice any negatives in handling, ride, or acceleration?

 

Either size is fine for your wheel and suspension. However there can be minimal difference when used in deep snow as a narrower tire will cut through with less resistance. Wider tires can corner with a little more grip but increase rolling resistance and lower mpg. Since the tire is mounted on the same rim width the difference is very small.

 

Minihue,
Thanks for your advice. Always appreciated. I think I will stay with the stock size. I don't track or autocross the car. I am not a "modder". I really like my car as is.