樓主過慮了，鑄鐵是主流，鋼的輕易變形，夾心的光纖的也有。太薄不是指貼層太薄就是總厚度不夠

https://carfromjapan.com/article/car-maintenance/what-are-brake-rotors-made-of/

conventional automotive brake rotors are cast from G3000 grey cast iron. These work well with a pad material designed to operate using adherent friction. Most of the European system rotors are cast from a high carbon G4000 grey cast iron.

不覺得普通日車會用夾層。