Might wanna make sure you didnt put the brake pads on ass backwards
sounds stupid but a friend did it on his civic and it was making a grinding noise saying the same thing "Dude its the new brake pads, I think they gotta brake in" RRRR wrong seems as if the pads dont like going the other way on the rotor and chewed its way threw it. Its like a ginda grinding/rattle noise. I would compare the noise to scrappy a needle on a pan.