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More than likely the rotors have some lateral run-out. Most cars have a maximum spec of .003" per face. Consider that rotors are not exactly a space-age engineering marvel by any means. They suffer from density variations and will warp as their various densities expand and contract at different rates as they warm/cool. Add in the fact that the shippers and delivery people toss them into the back of trucks, on the shop floor, etc.
I never install new rotors without chucking them up and taking at least a light cut to make sure they're not going to cause me any grief. It's an extremely rare occasion that I find one that doesn't have some type of deformity, right out of the box. That also goes for the rotors that come in boxes stamped "No resurfacing needed".
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ASE Certified Master Automotive Technician w/L1.
ASE Certified Master Medium/Heavy Truck Technician.
Certified EVT (Emergency Vehicle Technician)
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