I got cross drilled and slotted rotors for my 97 cobra convertible. I also got ceramic brake pads about 7 months ago. Now it seems after ive been driving for about 10-15 mins, they squeak when I come to a stop, but its not constant. Its random, but the more I drive, the more it seems to randomly squeak below 15 mph when I hit the brakes. Any idea what the problem is?