Since I swapped my rotors I noticed a chirping sound that is almost certainly a lug nut barely hitting something. When I first put the Renntech monolites on my SLK32, it was a ticking sound. The lugs needed to be cut which fixed the problem except under very heavy breaking when the brakes got hot. Even now, it only starts chirping when the car warms up. The lugs much expand just a little tiny bit and start hitting something. If I pull up on the e-brake handle just a little tiny bit, the noise stops.