Paul McG

Hi I've got a 57 plate r400h with 165000 miles on the clock. Love my car but I'm constantly having to take it to my mechanic as the brake on the passenger rear side keeps sticking on and making a grinding noise. pads and discs been replaced numerous times. Piston has also been replaced but get a couple of months and it starts to make that grinding noise again and back alloy looks rusty. anyone else had this problem? and if so how did they eventually sort it? Many thanks