Just replaced the warped rotors (and pads) on my 1991 190E. If you put the new rotors on, and tighten the allen screw it will spin like it has a LOT of runout. My guess is: the allens screw is just for minor alignment. What ACTUALLY holds / mates the rotor to the hub is the lug bolts.
When I put my rotors on and spun it (and saw that it "looked" warped) I just about had a heart attack. I don't know what the torque of the set screw is supposed to be but my guess is that it is not very tight at all. As a matter of fact, if it is too tight it wouldn't let the disc mate with the flange correctly.
By the way, on my just completed test drive it braked (?) like a dream, smooth as silk. I used Mintex pads and ATE rotors from PartsShop.
Somebody confirm my suspicions,
1994 C280, dark green metallic
1991 190E 2.6, Black
(sold to another forum member)
2003 Chevy Tahoe LT, Redfire Metallic
1989 Mustang GT Cobra Convertible