If you purchesed MB pads and rotors, you will need to seat them in, that is get them hot. I usually just go down the road and apply the brakes intermittently without letting up on the accelerator. 10 to 15 times at 50 mph or so is good enough. You will feel a noticabe difference right away. If you don't, try locking up the brakes forward and reverse 3 or 4 times. That should do the trick.