My 91 (DD) setup is: Rear 18x9.5 et 35 = No problems @ 15mm drop and 0.5 degree negative camber (tried to fit et 30, but no way with my tein super street suspension set to a 15mm drop! If anyone gets wider wheels than 9.5 inch on a Z at et 35 with a 15 mm drop without rubbing, are running with a S.T.U.P.I.D camber)
Front 18x8.5 et 30 = Rubs on bad bumps (but can live with) @ 15mm dop with 300 degree camber comp. kit.
Running 350z track rotors on the front with no spacers. Caliper clearance depends on wheel design.