Warning: Rant below.
So when I bought my 2006 Cobalt LS, it was a dealer dress-up including aftermarket wheels. With the aftermarket wheels, they used slightly different wheels in the back, identical to the fronts except for a slightly deeper lip created by angling the spokes back from the hub (same offset front/back) toward the center-line. I guess the deeper lip was supposed to make it look like wider wheel/tire combo in the back.
I went along with it anyway because the wheels themselves looked great. Unfortunately, this setup nixes the possibility of tire rotation, and I bought this car to be affordable. So I come up with the great solution to just get a set of Cobalt SS wheels and sell my old ones to make up part of the cost. I found a brand new set on craigslist for 400 bucks, and everything looked great until I realized: GM, in all its wisdom, gave 2006 non-SS Cobalts 4-100 bolt patterns, while all SS models got 5-110 bolt patters. AAAARGH.
End rant.