Brake rotor pitting

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I see this happen quite often, but what actually causes brake rotors to pit or rot out like this? Is the pockets in your casting? Or something else going on. Possible termites? Lol

Fwiw, these are OEM rotors and not super cheap China rotors.

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Sitting for too long allows rust to propagate deep into the surface. Cars need to be driven (or garaged) to keep the rust formation on the surface only. When my FIL's F-150 sat in a barn over the winter, the rotors would look like this. Eventually, we would take off the front wheels, and coat the rotors with grease to preserve them over a Vermont winter. Cleaning them off in Spring took a bit of effort, but sure beat replacing them every year.
 
Originally Posted By: Astro14
Sitting for too long allows rust to propagate deep into the surface. Cars need to be driven (or garaged) to keep the rust formation on the surface only. When my FIL's F-150 sat in a barn over the winter, the rotors would look like this. Eventually, we would take off the front wheels, and coat the rotors with grease to preserve them over a Vermont winter. Cleaning them off in Spring took a bit of effort, but sure beat replacing them every year.


I get that, but this truck is my daily driver. Never sits for more than a day or two.
 
Looks like the casting is rusting underneath and pits are the result. I have painted rotors with hi temp rust proof paint that will help but not stop this.
 
Originally Posted By: Johnny248
Originally Posted By: Astro14
Sitting for too long allows rust to propagate deep into the surface. Cars need to be driven (or garaged) to keep the rust formation on the surface only. When my FIL's F-150 sat in a barn over the winter, the rotors would look like this. Eventually, we would take off the front wheels, and coat the rotors with grease to preserve them over a Vermont winter. Cleaning them off in Spring took a bit of effort, but sure beat replacing them every year.


I get that, but this truck is my daily driver. Never sits for more than a day or two.


It did at some point...only fix now is new rotors...
 
Had the same issue with the last set of rotors on the '07 Explorer. Longest it has ever sat without use is a week - therefore I respectfully disagree that it is only caused by parking it for a long period of time.

Rotors were an AC Delco product (I know, on a Ford, but that was what the shop it was serviced at used). The outer surface was not as bad, but the inner surfaces were terrible - on both sides. Rotors had about 5 years and 50,000 miles of service on them. I've had minor salt pitting on just abut every set of rotors I've ever used over the years and chalk it up to salt usage in the winter. These were in another league of pitting though - I was horrified when I inspected the backside...

The only brake issue mine did have was both lower slide pins were badly corroded and sticking, leading to premature pad failure (and discovery of the severe pitting).

Don't believe any e-coating or other product is going to prevent this from happening as it is in the swept area of the rotor where no coating will remain for long.
 
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