Disks work better on a smooth serface. You pads might be glazed over with ALU from the disk... Take the pads out, and see if they are shiny, if so, sidepaper then intill they are not. they put them get in, and make sure the rotor is very central, then ride along with brake on really fast, and do lots of stoppies, then pour COLD water on it, it will/should sizzle, cause its so hot! and do that about 5 times, should work then