he just put new rotors on it.

his tire are most likely messed up, the steel belts tent to unwind under the rubber. his tire may even have a hop to it, or egg shape, but cant see or feel it till its going 60 mph.

i had i tire like this on my car when i bought it, thought it was a bent rim, but the tire was egg shaped when spinning fast. most tire balance machines don't do 60 mph, so you cant tell, they still balance on the machine.