So here's my dilemma. I have a 2007 Mazda 3i that has a rattling problem with the rear pads. When I hit any bumps in the road the pad rattles against the rotor unless the brakes are applied. I've done what research i can on the internet to find solutions to this but I am stumped currently. I believe this is occurring on both sides. A little background on what I’ve attempted....

So it started when i changed the pads myself and bled the brakes. I messed up and got air in the lines. Took it to a local shop and had them bleed the brakes so I didn't mess up anything further. This helped but did not solve the problem. As far as I know they did not cycle the ABS during the bleed. When I start the car and step on the brake the brake booster clicks on right away. It engages when the car is cold and does not engage as much once warm.

I've tried different pads from online, advance auto and auto zone. All with the same result. I’ve bought the pads with the spring that protrudes from the top of the pad (rather than the one with the spring on the back which would go with the 3S model with the 2.3L engine) and have placed the pad with the spring on the inside of the rotor. I believe the outside pad is the one rattling.

Any help would be appreciated as to what to check or look for. One question i did have is what keeps the outside pad in place? It seems that the retaining clip that attaches to the caliper would do it but it seems to just pop in to place and not touch the pad.

Thoughts? Thanks all.