STEPHAN, THIS IS GOING TO SOUND CRAZY, BUT CHECK IN THE BOTTOM OF THE FRT DUST SHIELD ON THE BACK SIDE OF THE ROTOR FOR A SMALL PEBBLE LAYING IN THERE , THEY WILL MAKE A HECK OF A GRINDING NOISE AND USUALLY ONLY WHEN THE BRAKES HAVE BEEN APPLIED FOR 4-5 SECONDS , THE ROTOR GETS HOT AND SWELLS A LITTLE BIT TRAPPING THE LITTLE ROCK BETWEEN THE ROTOR AND THE SHIELD , HAVE SEEN THIS NUMEROUS TIMES , , HARD TO BELIEVE HOW BIG SOME OF THEM CAN BE TO GET IN THAT TIGHT A SPACE , I HAVE SEEN THEM AS BIG AS MARBLES ,, JERRY