As someone who's replaced numerous sets of rotors on Audi cars over the years, due to surface rust, I'm curious to know if the Model S Brembo rotors are high-zinc content rotors. In New England, a car does not have to sit long before you start getting surface corrosion on rotors. Driving the car then imbeds the iron oxide into the brake pads, and before long, you've got chattering brakes. After of years of dealing with this on several Audis, I finally upgraded to high-zinc rotors and the problem went away for good.