warped new rotor?
 

Installing new ATE vented front rotors on my 02 Boxster S and discovered a severe wobble in the left rotor. Reinstalled it several times, still there. I removed it and checked the runout at the hub and it was negligible so I'm sending the rotor back. It must be warped. I'm a bit surprised. These are not bargain-basement rotors. Then again, they're not super-expensive OEM either. I have a replacement on the way. Is this rare? Or not so rare?

Since I replace my pads and rotors at least twice a year, I have gone through a lot of rotors over the past 6 years. In that time I've had one rotor that was actually warped.

However, I recently had another rotor that needed the center hole to be opened up a few mm so it would fully seat on the hub. It would get 95% of the way onto the hub (visually it looked fully seated) and then bind on the hub alignment tabs. The rotor acted like a warped rotor on the car but had no runout at the hat or at the outer edge of the rotor on the bench. WTF? Then I checked the hub and it was fine. WTF #2. I installed/removed it four times before I finally found the seating issue which I was able to fix it with a hand file.

So I'd say that while manufacturing defects are somewhat rare, they can and do happen.

May simply be from improper storage, the braking surface should be at the bottom so it rests on the shelf flat surface.