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I have one rear rotor that is partially rusted on the braking surface and the rust won't go away. I tried scraping down the surface to even it out, and then the entire surface looked rusted. I had hoped that the pads would wear away the rust to expose the braking surface underneath, but only part of the rust wore away. I took pictures of the right rear pad before and after the scraping down, and also what the left one looks like for comparison. It seems like there is still a good deal of life left on the left rotor and also the pad, so I don't want to prematurely replace them if I can still get a good amount of use out of them. I am wondering if replacing just the right rotor would be alright, or if it looks like I'll have to replace the left side rotor/pads soon anyway and I should just do both rotors at the same time (and also do the pads while I'm at it). I have attached the following photos:

  1. Right rear rotor before scraping
  2. Right rear rotor after scraping and driving a few weeks enter image description here

  3. Left rear rotor

  4. Left rear pad enter image description here

Edit: my car is a 2007 Mazda 3 GT 2.3L

Edit 2: After I scraped the rotor, I tried using just the hand brake to stop to scrape more of the rust, and the brakes would kind of pulsate, as if the pad was partially catching on some parts of the rotor only. It eventually started doing this when I use all four brakes and get close to stopping, but it's much more pronounced when using just the rear brakes.

  • What is the make/model and year of your vehicle? – DucatiKiller Feb 29 '16 at 0:06
  • 2007 Mazda 3 GT 2.3L – Pedram Feb 29 '16 at 0:07
  • I would say yes. Your anti-lock will have different friction coefficients on each rear brake and it could cause instability under high speed high friction braking. Just IMO. Let's see what the community says. – DucatiKiller Feb 29 '16 at 0:09
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Provided that the other disc is still within acceptable tolerances with regards to width, you can replace a single disc. I personally prefer to replace discs as a pair on the basis that if one side is worn close to its useful life, the other is likely in a similar state. You could look at having the discs turned on a brake lathe as an alternative to replacement but I suspect there isn't enough metal on the rusty disc to make this a viable alternative.

I would strongly suggest that you check the operation of the caliper, brake slides and ensure that the pads or piston on the rusty sides caliper and not jammed / faulty. Looking at the wear exhibited, it would suggest that braking effort is not being correctly applied to the rusty disc.

  • I took the pads off and filed and lubricated the parts that slide along the caliper, and also lubed the pins, and now the pulsation is gone and I can see the rust on the rotor being scraped away. Looks like the caliper was seizing, which was causing the pad to not rub on the rotor properly and letting it rust. – Pedram Apr 20 '16 at 4:57
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If this is a vehicle that is driven regularly I would check that the rear brakes are working correctly. When things are working correctly the pads should remove the slight rust that forms. That is a lot of rust for a vehicle that is driven frequently. You can do a simple test by raising the rear wheels. While an assistant steps on the brakes see if you can turn the wheels by hand. (they have to be really bad to see this) You can also try a panic stop on a sandy or gravel section of driveway and check for skid marks. I believe either the pads are seized in the mounting brackets or the caliper is not moving on the slides.

  • Yes, it's driven somewhat regularly (about four days a week). The second rotor picture was after at least 3-4 weeks of driving. I thought the rust should have been gone by then. Also, after I scraped the rotor, I tried using just the hand brake to stop and scrape the rust more, and the brakes would kind of pulsate, as if the pad was partially catching on some parts of the rotor only. It eventually started doing this when I use all four brakes, but it's much more pronounced when using just the rear brakes. I'll try raising the car and pulling the hand brake and see if I can turn the rear wheel. – Pedram Feb 29 '16 at 6:16
  • I raised the right rear of the car and tried turning the wheel by hand while the hand brake was applied and it wouldn't budge. When I released the brake, it would turn fine. There was a slight resistance and I could hear a slight scraping sound while it turned (the wheel would come to a stop after I let go and wouldn't continue to turn by itself). So it seems the rear brakes aren't seized and are applying resistance. – Pedram Feb 29 '16 at 21:32
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2015 CRV and 14,000 miles both the front and the back rustic took it to Honda dealership Marysville was $191 they turned him down lasted three months on the rear. The rears were ground down on September 14 took it to a non-Honda on September 27 dealer they replace the new ones for $197 and they're still in good shape. I was advised by the Honda dealer that they would have replaced them with the same cards would have been $127 per drawing not including labor. I was also advised my service manager or employee that they, The facture using cheaper rotors.

  • Welcome to the site. I'm not quite sure how this answers the question of "should I" or "do I need to" replace both rotors. Just curious if you could take a look at your answer and maybe edit as needed for clarity? – Pᴀᴜʟsᴛᴇʀ2 Jan 2 '17 at 18:42

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