The factory had "swedged" the lug studs against the rotor/hub assembly,they put just a slight shoulder on the studs, to hold the rotor tight to the hub..--this is "lost" once the studs get pounded out and replaced when a new rotor is installed--but I've not had any issues with looseness after tightening the lug nuts to the right specs..if a stud was not fully seated in the hub it can seat after you have driven it awhile,but the lug nut would be loose if that were the case..