If you ever wondered why brakes squeal, this is why.
It’s actually caused by lack of lubrication on the back of the brake pad. You can see here the areas where the two pistons contact the pad are still lubricated, but the lubricant has worn off everywhere else.
It’s actually kind of interesting how the vibrating pad has worn through the paint –
Strangely enough it was only on the outside pad. The inside pad didn’t lose any lubricant –
And here’s the problem pad with new copper anti-seize applied –
Although the squealing sound itself is only annoying, not dangerous; in this case it caused a real problem because it started at the exact moment as an emergency brake was failing. I thought I only had one problem, and it was in front. Because I’d replaced all the pads and rotors recently, my first thought was that the wheel bearings (nearly 200,000 miles on them) were going. I jacked the truck up and tried rocking the wheel, it was rock solid. Maybe the bearings were only starting to go? Maybe a 4WD half shaft was starting to go? I thought that up until the moment an emergency brake shoe broke loose and disintegrated; which made a sound like the back end of the truck had exploded. That was a nasty surprise, and I just happened to be riding down Main Street at rush hour when it happened. Better that then the highway, I guess. I might have found the problem if I hadn’t let myself be convinced the problem was up front.