KW Variant 3 Coilover question....
 

I am going to be buying a used set of KW Variant 3 coilovers from my friend. It has 11K miles on them and he tells me that everything is in great condition except that he said:

"The only problem that bugs me is when the bumpstops in the rear reach the top of the fender it can get squeaky."

He said he tried it on 2 sets of his cars and both did the same thing.

Is that normal for upgraded suspension for the 370z?