Hey guys so i know a lot of you guys are experiencing a loud and annoying rattle coming from the rear of your mazda 3. I was one of them, i fixed mine and a lot of guys says they have to from switching brake pads. Its true. I replaced my rear pads and threw on new ones, no more rattle! Im so glad cause i was going insane. To test your pads go to a known part of a road that causes rattling and when your driving through there, pull up on the parking brake to apply pressure to the pads, if the noise stops that is your problem. My pads had plenty of materiel on them but the issue is they put a spring on the outer pad that hits the caliper on the rough roads. If you have any questions please ask.