I would have guessed something broken in the ebrake system in the rotor hub, because I haven't seen the pads have a directionality when they start making noise, but I certainly haven't seen it all yet. Yes, they are simple. I was camping so I didn't post up whtn you needed the hint, but when you pushed the pistons back, I hope you were bleeding the fluid out instead of pushing it back upstream past the ABS valves and so forth.
