Run flats are very noisy, ride hard, wear out in 30,000 miles , I will change them this week to Cont. Extremes. I have read that the Mich. run flats get side wall bulges, this seems to be from hitting chug holes.
Just bought my 2013 ATS three weeks ago, the first thing I did was get rid of those tires, terrible ride, very hard and noisy. Read the reviews on runflats and they are not good. The tire is too heavy and has too much rubber. I bought Blizzaks for the winter last week and the ride is 100 times better, and that's with snow tires! In the summer I will be getting Potenza Pole Position tires and I just purchased Advanti HyBris aftermarket rims. I will never put runflats on any car I own....ever!