I have 2 new front brake discs that I got from this site. The car was vibrating quite a bit in the front end when braking, and the abs was reacting to the vibration. When I removed the wheels, I found that both discs had 2 low spots each. The spots are located directly opposite each other across the diameter of the wheel. Did I get a bad set of discs, or is there some other problem or adjustment I have wrong?