One problem related to brake grinding noise has been reported for the 2011 Mazda CX9. The most recently reported issues are listed below.
I have been having issues with the brakes mostly when raining or snow. At times when I go to hit the brakes they get stuck or make a grinding noise and don't want to stop. This has happened numerous times and almost caused me to hit another car on multiple occasions. I will take it in soon to have it checked now that I see that I am not the only person with this issue. Starting in Jan 2015 I notice a burning smell coming from under the hood of the car. I had an oil change and checked for an oil leak to find nothing wrong with the vehicle. After running the car for at least 20 minutes the smell continues.