While on balance, vibration and front end components, I recently installed a new set of front rotors - Balo - on my 1990 300E 2.6 (95K). I was careful to thoroughly clean the hub so as not to leave any residue that might cause uneven setting of the new rotors. While installing one of the rotors, I noticed what looked like a "V"-shapped piece of the metal missing from one of the interconnecting "webs" (probably not correct term). The edges where the piece was gone were very smooth - not jagged like they might be if a piece had been broken out. Thought the missing piece might have been machined out to achieve balance. After installation, I noticed a very slight vibration around 55+ mph that had not been there before. I don't believe this is tire related because I had the tires re-balanced, then a new set mounted and road-force balanced. The pedal also does not feel quite right - a barely perceptible bit of pulsation at times, almost as though there is a VERY SLIGHT warp of the rotor. Again, I thoroughly cleaned the surfaces and was careful to torque everything to spec. Is it possible for a rotor to be out of balance? Is some metal machined from the web during the manufacturing process to achieve proper balance of the new rotor? I discussed this with someone who said he has been involved with NASCAR and he said he has never heard of a rotor being out of balance or of how to check the balance on a rotor.