Do I need to replace just my one rusted rear rotor, or do I need to replace both rear rotors?

Question

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

3. Left rear rotor

4. Left rear pad

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.

Answer 1

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.

Answer 2

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.

Answer 3

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.