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Our car has only about 22k miles on it, but it's always been kept outside (in NY) and went for several months this winter with no use. This summer, we developed a low grinding sound when braking. A visual inspection shows there's still a lot of brake pad left, but the rotors are seriously scored with grooves and rather rough to the touch. The rear ones are worse than the front and the sound seems to be coming from those. My question: should I just live with them as they are until the rough rotors wear the pads down and then replace everything, or should replace the pads early and get the rotors ground?

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  • Your choice. The pitting will wear the pads faster. The pitting will make noise. The pitting could cause excessive heat = more wear and possible harm to the calipers and fluid. If you replace anything or everything and this car's lifestyle doesn't change...you'll be asking yourself this same question in a few years. Sometimes, this is just one of your specific expenses that your car and driving habits incurs. IMO, leave 'em until they wear out, but keep your eyes/ears open for excessive heat signature and worn pads. Cheers!
    – Ted Pants
    Aug 15, 2017 at 0:56

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I know this is long ago, but people will view this thread, so I thought I'd post an answer.

Problem is your caliper needs to be rebuilt or replaced.

Internally, the caliper piston will gum up/varnish over time, and the square-cut seal becomes brittle or fatigued. As a result, the piston will start to become sluggish and won't return properly when you let off the brakes, causing the brake pad to ride the disc. This failure/maintenance requirement is inevitable, but is greatly accelerated by overheating the brakes.

I'm guessing you noticed some shimmy on breaking after you've been driving for a while too, which happens because the rotor heats up too much when the pad isn't releasing fully off the rotor. Failed caliper piston return also causes the brake pads to wear unevenly, with the inner pad wearing much faster than the outer one.

If you're experiencing repeat uneven brake pad wear and shimmy on braking, it's likely you should replace the rotor too, even if it's not scored. Oonce it's been overheated several times in the past, it will continue to "re-warp" once it gets hot, even at normal operating temperatures. That will cause the shimmy, denature the lubrication on the slide pins, cause the pads to wear unevenly All that will overheat the caliper further, which will then cause the caliper piston return problem to reappear. Turning the rotor won't help, either. A new one that has never been overheated won't warp when it gets up to hot operating temperature like a previously overheated one will.

On the caliper, everyone likes to just replace the caliper, but cleaning, lubricating, and re-gasketing a caliper (aka "rebuilding") is easy as can be, way cheaper (like $8 instead of $100), and keeps things out of the landfill. It's not really necessary to hone the cylinder when rebuilding a caliper because if it's rusted or pitted, you should just replace it. So if you find the piston or cylinder is pitted, forget it, buy a new caliper!

You should also change your brake fluid, because it's also been overheated.

Hope this helps!

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  • you might want to read the question one more time,the question is about rotors and pads.the calipers are not a part of this question even if they might be bad.
    – trond hansen
    Oct 14, 2020 at 8:13
  • I think your diagnosis of the calipers not returning may be spot-on for a couple of reasons; 1. we had been living in NYC and did a lot of hard breaking and stop-and-go driving. 2.I actually felt the discs a few times to see if they were wearing more on one side than the other and I recall them being very hot on one side and not the other. Obviously the mechanics at the dealership never suggested caliper rebuild fix, and I could have easily have done it myself. Regardless, we've since traded the car in, so it's someone else's problem now!
    – C.List
    Nov 29, 2020 at 18:04
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If the pits are really deep, then grinding may not be an option - there is normally a minimum thickness specified.

I would suggest that you save up for the new pads and rotors and change them when ready. That is ONLY if the existing ones are stopping the vehicle as they should - a bit of extra noise is not an issue as long as the stopping power is there.

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So this question has been viewed a lot and I wanted to post a followup: I ended up replacing the pads all around, and the rotors on the left side of the car that were really pitted (rotors on the right side were totally smooth) - this was at about 24K miles. Just now, at 45K miles, I got a break pad warning light on the car. Since I had to take it in for regular service, I asked them to check it out since it looked to me like all of the pads still had wear on them, but I was noticing the same sort of un-even scoring ont he rotors that I'd seen before.

The dealer said the pads were worn down on the hard-to-see (and hard to feel) inner side of the rotors and the rotors were once again worn very unevenly to the point that they should be replaced. I told them to go ahead, since I didn't have the time to do the job again. This seems super-excessive to me, and really weird - I've never seen this before in my 30 or so years of car ownership and DIY mechanic-ing. Then again, there are times of the year where this car goes for days to weeks at a time without being driven. This last time was the first time I have ever had someone other than myself do the brake maintenance on a car - since it's such a simple job.

Note that the car is a 2014 BMW X3, and has otherwise been fine.

...very weird. I will probably be trading in the car in the next 12 months and I'm looking forward to not having to worry about it.

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The rubber sleeves that the slide pins ride on need to be taken out of the caliper and have the bores brushed out because they corrode over time. The build up squeezes the bushing and the bushing squeezes the slides so only the piston side does most all the braking.

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    Aug 21, 2022 at 18:32

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