Two problems related to brake disc pads have been reported for the 2012 Mazda CX9. The most recently reported issues are listed below.
Brakes were occasionally �tight�, had to be pushed very hard to get the vehicle to stop. When I pushed the brakes it sounded like air was being pushed out. Changed pads and brake fluid, flushed the air out. Only made it worse. Now the brakes are constantly �tight� and after learning this is a common issue with this vehicle I'm going to replace the brake booster. Ridiculous that so many are having this issue and Mazda isn't recalling this part!.
I noticed that at very slow speed (backing out, easing forward) the brake pedal was very hard, did not depress, and car was difficult to stop. I did not have much of a problem at regular (60 mph) speed. Only once was there a loud hissing on the drivers side when the pedal was depressed. The dealer told me brakes were fine but the car did not drive fine. I took it to my mechanic who told me I needed front brake pads. Upon changing brake pads, I was told the brake booster was bad and causing the pads to wear abnormally fast and that the problem was actually worse with the new pads. Definitely a problem as I was only at 31,000mi. I didn't not return to the dealer and had the mechanic do the repair right then. What I thought was minor maintenance turned into a $500 repair. I found out later that there is an extended warranty of 7yr/90,000mi on the brake booster if diagnosed and fixed by a dealer.