The stock BMW brakes (in my experience) are fine - they still work even after the dust boots melt away and the calipers turn a funky color. It could be significantly less expensive to cool them with water.
What I'm wondering about is if it would be best to:
1. Mist the air with a very fine water spray leading to the rotor/calipers.
2. Directly spray the rotor.
3. Directly spray the caliper.
I did some math that I think is correct:
You specify vehicle weight, front and rear rotor weight, and start and end speed. The app calculates the temperature rise of all 4 rotors.
I know the front rotors weigh around 21.6lbs - anyone know how much the rears weigh?
What's interesting is the temperature of the rotors will rise about 50 degrees F if you stop from 50MPH. However if you slow from 100MPH to 50MPH the rotors will increase in temperature by about 150degrees.
I'm pretty confident that the temp rise is correct, but the amount of water required that I'm calculating might not be right yet.