Sometimes I take pictures of automotive curiosities and by the time I get around to looking at them again I’ve forgotten what’s curious about them. It took me a minute to notice what was wrong with these disc brakes. I’ll give you a hint: My co-worker Hans who was working on this Jeep Grand Cherokee was told by the customer that the brakes were squealing.
It’s not entirely clear from the photo exactly what’s going on, but the bottom end of the shim between the brake pad and the caliper has rotated toward the hub and started to wear a groove in the “hat” part of the rotor. If that groove had managed to cut all the way through, the caliper would have grabbed hold of the rotor and stopped it, but the wheel would have kept on turning.