I bought this 2017 Mazda 6 GT from the dealer as a CPO with full warranty. During pre-purchase, I had noticed that front brakes were done as the rotors looked new and when asked why not the rear, the salesman said that they were still good. I bought this car with 35K miles. 5K miles later I've noticed a lot of steering wheel shaking during braking even at slow speeds (20 to 40 m/h), so I decided to look into it. First I called the dealer and they said that brakes would not be covered under CPO so I decided to look at it myself (I normally do my own maintenance on my cars). The rear brakes were shot, maybe 20% of the pads left and rotors were so rusty and pads seized inside the caliper bracket. See the pictures.

It looks like Mazda is using very poor quality brake rotors as well as in my opinion a design flow in the fact that they are not using brake hardware in the rear brakes only in the front. From the pictures you can see that these brake pads were not moving to and away from the rotor like they supposed to due to excessive rust. I decided to change out the pads along with the rotors to get possibly longer performance out of the braking system. I went with Akebono pads and fully zinc coated brake rotors inside and out. Hopefully this will get me another 40 to 50k out of the pads and rotors.

The front were in better shape as it had only 5K miles but needed to be changed due to being out of round. I changed the pads as well. Talking to other Mazda owners on message boards it looks like the brake problems are more common than one may think, especially excessive rust. Actually the whole undercarriage is showing excessive surface rust as well especially for only 4 years old vehicle. I live in Chicago.