This is exactly why I am afraid to buy a new CTS. I had the original CTS and had no problems. I also rented a new CTS with the 17's and had no problem. Like you I have owned other cars with performance tires including 4 E39 BMW's and a Solstice with the GY F-1 tires, and none of them shimmed ever, including my M5 even when I drove it in the dead of winter (on dry pavement I might add :)).