Good comments, Gents. But let me add just one more thing (ain't there always just one more thing?) The rotor should be carefully deglazed and cleaned when new pads are installed. Wipe it down with solvent to remove brake dust, oil, and grease, whether you see any or not. Then sand the surface with medium sand paper to remove glaze and any trace of old compound. Use "garnet paper" for this, that's the kind with actual sand on it; aluminum oxide wet-or-dry paper will leave traces that will contaminate new pads. Then wipe down with solvent again.