Jack the front up, remove the wheels, and run it in gear. Watch for a caliper that is moving back and forth sideways as the rotor turns. Look for spots of rust buildup between the rotors and hubs that prevent them from sitting flat. If this started weeks or months after you replaced the rotors, they might be Chinese parts. There's nothing wrong with them but cast iron parts need to "age" 90 days before they are machined. Chinese parts are cast, machined, and shipped right away, then they age on your car. A simple machining will usually solve the problem permanently.
April, 10, 2011 AT 7:40 PM
If your pedal pulsates when you apply the brakes: * Pedal pulsation is caused by excessive run-out in the rotors or drums that are out of round. These conditions occur due to excessive heat.
* It is important to differentiate a warped rotor condition from ABS operation. When the ABS kicks in the driver may experience pulsation in the brake pedal. This could be confused with a warped rotor.