I have a BMS warning sticker in the top right corner of my windshield that specifically warns against use brake dust shields.
They need the air flow for cooling. Also the brake dust has to go somewhere, so it will cover all the components and degrade them as well.
2004 E60 530is, Delivered 12/12/03, TiSilver/LGrey, PP, SP,PS, PDC, ACC, FRS, Step, Xenons, clear bra, body colored rear inserts. (Retired, 1983 henna red 320is)
2004 Corvette Z06 Commemorative Edition