[Winklovic]

Car: 2010 Mazda3 GT Sedan with 104,000 kms. I'm assuming these are the original rotors, as I purchased the car three years ago, and haven't replaced the rear rotors.

My brakes had been making a lot of noise lately first thing in the morning. After a couple blocks, the noise would disappear. I assumed it was rust causing the noise as I park in an enclosed parkade that is more humid than outside. Talked to my shop and they agreed.

I decided to take pics of the rotors the next morning. Upon closer examination, I spotted what looked like a crack in both rotors, just off the braking surface in the hub, that ran the circumference of the brake rotor. I sent the pics to my shop and they agreed they were cracked.

They are getting replaced today. Front rotors are fine.

Has anyone seen this before?

 

[AD13]

It doesn't look like they are cracked. Just corrosion build up on section that hasn't been worn away by the brake pads. My original rotors looked similar at 130k. Although they didn't make any sounds, they were warped and replacing them got rid of steering vibrations at high speed. I went with coated rotors to make sure rust didn't build up again.

 

[kms1990]

I would replace them, brakes are not something to screw around with when they have an issue. get good pads (top line max, GT at autozone are good, hawk if you want premium or more track like pads (will be harder on rotors), stoptech or centric all make good pads) so does wagner and akebono its more brand choice and availability I like the duralast ones because the no hassle warranty when I need new pads just bring the old ones to autozone and swap em for new ones. the max branded duralst pads they sell are about $50-70 an axle but are good ceramic pads with low dust and good stopping power but I would avoid their rotors theyre just cheap generic Chinese crap I currently have wagner e coated premium rotors on my xterra and they seem to be really good.

 

[Winklovic]

Well, this is embarrassing.

I took the car to the shop, the shop took the wheels off, examined the rotors as bed they could and could not find any cracks. They did say there was a small lip at the edge of the braking surface and they believed the position of the flash created a shadow that looked like there was a crack. He said they could replace the disks and pads if I wanted, but there wasn't a reason to. I said, okay, I won't.

When I got the car back, I tried the flash experiment: one pic with the flash above the lens and one pic with the flash below the lens.

AD13 was right!