Brake rotor rust - indicative of caliper issue?

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Attached is a photo of one of the rear rotors on my '03 Explorer. All four rotors look similar, although the rust is a bit more scaly on the rear. All four corners need new pads, and based on the amount of rust on the rotors, I plan to replace them as well. What I'm looking for input on is the ring of rust around the outer edge of the pad contact surface on the face of the rotors. I realize a small lip of rust in that area is normal, but this seems to be a bit much, and definitely overlaps the pads in that area, so it seems there should be pad contact there by design. Is this caused by the caliper pins not functioning correctly? If so, it is likely that servicing the pins when I do the rest of the work will cause the calipers to function properly again? I'm trying to put together a Rock Auto order, and would like to order the calipers along with everything else if it is reasonably certain I will need them. If the pins need to be inspected to determine whether they can be brought back to life, I could order the pads and rotors from Rock Auto, then get calipers locally if they are found to be needed during disassembly. Any input is appreciated!
 
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I think the pins are ok--when the freeze it's the inner pad that still moves. They might be sticky but that looks like rust that simply worked its way down over time.
 
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Probably a frozen slide pin. You won't be able to get it out, so just get new calipers. Rock Auto has Raybestos Element3 all-NEW calipers at a good price. That would be my choice smile While you're there, get coated rotors.
 
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It could also be the pad ears swelling from rust and getting stuck in their grooves. You can clean up old pins, but if you nick their "teflon" coating, they'll corrode quickly and jam up again. Best bet is to use the (new) brakes more, and give them a few good forceful stabs at speed now and again. If they install tightly, file or grind the ears.
 
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Yes. Incorporating a brake service twice a year would help to prevent this. Cleaning and lubrication should suffice.
 
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Salt corrosion. It's possible that the calipers can be saved by wire brushing and painting. That's an awful lot of work and you won't know if they're salvageable until you get them off. You would be better served to replace everything. You are going to have a problem getting the bracket bolts out and they will need replacement too. If you buy from Rock Auto, go with Raybestos.
 
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I think the outer ring of rust is nothing to be concerned with. New coated rotors and high quality pads. Clean up the calipers including the pins. Wipe the pins clean. If rusty replace, don't wire brush. Make sure new clips come with the pads. Lubricate in the proper areas with right lubricant. Amazon is a good place to also look for pads & rotors. Rotors are expensive to ship from RA.
 
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Originally Posted by MParr
Salt corrosion. It's possible that the calipers can be saved by wire brushing and painting. That's an awful lot of work and you won't know if they're salvageable until you get them off. You would be better served to replace everything. You are going to have a problem getting the bracket bolts out and they will need replacement too. If you buy from Rock Auto, go with Raybestos.
There's actually probably nothing wrong with those calipers. Surface rust like that is normal. You can clean it off but it will return....
 
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I've had brake rotor rust issues like that on vehicles/brakes that were meticulously maintained and well lubricated. Seems to me that it mostly occurs on vehicles that are exposed to the weather (not garaged) and/or salt and aren't driven daily where rust would be continually worn off. That's been my experience, none of my daily drivers that are driven regularly have seen this issue.
 
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I think what he is asking is if the shiny clean area should extend closer to the rotor edge. If yes, then what is wrong with his calipers and/or pads that he is not achieving better contact. Here's a picture of what I think we should be seeing (top) vs. the bottom picture which is more exaggerated than the OP [Linked Image from i.stack.imgur.com] [Linked Image from attachments.priuschat.com]
 
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Originally Posted by doitmyself
I think what he is asking is if the shiny clean area should extend closer to the rotor edge. If yes, then what is wrong with his calipers and/or pads that he is not achieving better contact. Here's a picture of what I think we should be seeing (top) vs. the bottom picture which is more exaggerated than the OP
The lip is caused (or allowed) by the pad design itself. It's simply not quite tall enough but on the other hand, I presume you don't want the pad to extend past the rotor's edge either. The caliper, and especially the pins, have no bearing on the pad being able to move 'up' or 'down', only side to side. The caliper bracket determines the brake pad's position though.
 
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Originally Posted by doitmyself
I think what he is asking is if the shiny clean area should extend closer to the rotor edge. If yes, then what is wrong with his calipers and/or pads that he is not achieving better contact. Here's a picture of what I think we should be seeing (top) vs. the bottom picture which is more exaggerated than the OP [Linked Image from i.stack.imgur.com] [Linked Image from attachments.priuschat.com]
You are correct. The shiny clean area is narrow and does not extend nearly as far to the outside of the rotor diameter as the pads do, which doesn't make sense unless the caliper is not functioning correctly. That, or as supton suggested, the rust may have worked its way inward and swelled that visibly rusty area over time. I do appreciate all of the replies. With that said, it seems difficult to pick out a common thread of a single likely cause of the symptom I am seeing on the rotor. Many good suggestions though.
 
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Originally Posted by eljefino
It could also be the pad ears swelling from rust and getting stuck in their grooves. You can clean up old pins, but if you nick their "teflon" coating, they'll corrode quickly and jam up again. Best bet is to use the (new) brakes more, and give them a few good forceful stabs at speed now and again. If they install tightly, file or grind the ears.
I saw this on my truck a few years ago, and the pad ears were very rusted.
Originally Posted by Donald
I think the outer ring of rust is nothing to be concerned with.
No its concerning, thats a good bit of lost braking surface area. Reduced braking efficiency.
 
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Up to you, the surest way to know if you need calipers is pull them and inspect for leaks, torn boot, and piston intact (not cracked/chipped if composite instead of metal). Otherwise, the old calipers can have the rust cleaned off the mating areas to the bracket, pads. and reused, but you'd also want to inspect not only the pins for rust but also consider replacing the bushings if the pins are badly rusted as that may have worn them. Rock Auto sells both the pins and the bushings separately. I'd not be too concerned with the prior wear pattern if you're replacing at least the pads and rotors, and pins and bushings if needed. Do that and clean up the rotors of rust and you're starting with a clean slate. The thing to be concerned about is if the wear becomes this irregular early in the pad lifetime. Coated rotors will not make a difference in this respect, in a rust prone area all they're going to do is keep the interior cooling vanes more open which is most useful for towing or otherwise spirited driving with excessive brake use. wink I mean if you are concerned about hub-rotor contact rust, you can put some silicone lube there too. The coating will wear off by itself so eventually you'll need something, or to pull the rotors more often so they don't get stuck on.
 
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I would dunk the rotors in Phosphoric acid. Wait & then after measurement decide if you need to replace them. Calipers would benefit also.
 

JHZR2

Staff member
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Ive noticed this irregular contact, and the semi bright/semi rusty surface on my accord hybrid. Because that car recovers energy, the brakes dont do as much work. To me its normal, though not necessarily desirable. It indicates, IMO that you need to do a few hard stops, and maybe a bit of driving riding the brakes slightly to get some heat and a bit more contact in there. See what happens after that. Surface rust on the rotor is normal. This inconsistent and deeper, harder to shave off with normal stopping type rust is more concerning and more unsightly, but im not sure its overly uncommon.
 

Kestas

Staff member
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I've had wear patterns like that on cars that see seasonal storage, but the brakes are otherwise in good condition. Does your Explorer see any storage?
 
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Originally Posted by fsdork
You are correct. The shiny clean area is narrow and does not extend nearly as far to the outside of the rotor diameter as the pads do, which doesn't make sense unless the caliper is not functioning correctly. That, or as supton suggested, the rust may have worked its way inward and swelled that visibly rusty area over time. I do appreciate all of the replies. With that said, it seems difficult to pick out a common thread of a single likely cause of the symptom I am seeing on the rotor. Many good suggestions though.
Interesting thread, but back to square one (captain obvious). As usual, Dave9 sums up the answer with good logic. In my video links above, the evidence appears to show this is not an uncommon problem with these brakes. Bad design or bad maintenance in corrosive environments?? Yet, below is a picture of the same brakes with a very wide wear pattern. No clear answer. Clean everything up well, install new rotors/pads, and monitor the situation. Or, install new calipers/rotors/pads and monitor the results. Let us know what happens fsdork. The pad ear design sure is different than most. Off centered, creating more twisting force IMO (lever action). Maybe the ears require biannual cleaning and lube with Molykote77 or Pastelube??? [Linked Image from lh5.googleusercontent.com][Linked Image from m.media-amazon.com] Sorry, I love pics..... where's the engineer to confirm my poor design hypothesis??? [Linked Image from gtsparkplugs.com]
 
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Originally Posted by Kestas
I've had wear patterns like that on cars that see seasonal storage, but the brakes are otherwise in good condition. Does your Explorer see any storage?
No storage, but it does live outside, and doesn't see a lot of mileage. From October to present, it has accumulated approximately 3500km, most of which is local short tripping. Certainly not an ideal set of circumstances for keeping rust off of the brakes, but I'm not sure it explains this specific issue. If the rust were more consistent across the rotor's contact surface, that would be a different story. I agree that the issue of corrosion on and around the pad ears seems like a logical possible cause. One other note I didn't mention in my original post, is that the pad wear seems to have conformed to the rust, with the friction material being thinner where it contacts the rusty area. This suggests to me that either the caliper and pad combination is producing more force closer to the hub (shiny area of the rotor) than it is over the rusty area, or the rusty area of the rotor has swollen and there is something about the altered composition of that area which keeps the pads from scrubbing the rust off of the surface. Or, again, the pad ears aren't moving as they should and are binding, which would make sense as a cause of my issue. It seems as though replacing pads and rotors as well as servicing the caliper pins (and making sure the pad ears travel as they should) is the reasonable course of action based on all of the great input I've received. If I find the caliper pins and bushings are an absolute disaster when I get them apart, I will address that accordingly.
 
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