Minnesota uses too much salt! Even on days when the temp is too cold for the salt to work. Most of my rotors have a rusty lip (4 cars), but I have never seen the lip fall off. Of course, if you change pads and not rotors, which for me is every other time, the new pads will touch the lip and wear a lot on the edge. It looks like that the new pads somehow covered the lip and wore off the rusty area.

Poor condition guide pins will do that.

I like Brembo and Akebono combination. I plan on that with my daughter's Subaru next month. Perhaps I should just order new guide pins just for fun?
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Keeping it running is better than buying new