Uneven Brake Pad Wear on One Caliper

[sicktim]

My wife's car, a 2012 e92 328xi, had a grinding sound when braking. Turns out one of the rear brake pads were worn down to nothing. What is peculiar is that the other pad on the same caliper had quite a bit of thickness left on it (about 1-2cm). I thought that the guide pins might be stuck, but they weren't and they moved freely. I greased them up anyway and put it back on the car (new pads and rotors of course). The other side had more even wear. I'm a bit lost other than maybe there are other factors that cause the caliper to not slide correctly on the guide pins. Anybody have some light to shed on this matter?

On another note, i'm glad my wife noticed something was wrong (I believe some would ignore this problem). It was on the caliper that doesn't have the sensor so there wouldn't be any instrument warning.

[BaltimoreBimmer]

You could have a sticky caliper. This is not at all uncommon.

[MIKYZZ4]

Since you confirm that the guide pins are not the problem,
I would also suspect sticking calipers, just be sure this is not a symptom of another problem,
Like corrosion due to lack of brake fluid flushes, otherwise the symptoms will continue to occur!