Ok, so the story goes that about 12 months ago the front brake pads and rotors were replaced and I was told at the time that the rear pads needed to be changed pretty much immediately as well. About 5 weeks ago the Check Brake Linings alert came on and I figured that the rear pads had finally served their time and I'd left it a little too long. I ordered a full set of Hawk Ceramic pads, as well as front and rear wear sensors. When I pulled the rear pads off (3 weeks after the warning light came on) there was still a considerable amount of life left on them. Oh well, they are off now, I changed the pads over, and the sensor which had done its job. About two weeks later the brake pad warning came on again, so I figured maybe the front ones were due again. Pulled the front pads and noticed that yes the sensor was warn through, but the pad wear was very uneven, not just when comparing left wheel to right, but inside to outside on the left was noticeably different as well.
This first photo is the front left and right pads which isn't a great photo
The second photo is just the front left pads (inside is worn down), and I am assuming that when the pads were replaced, the sensor wasn't fully seated against the pad carrier, because I pushed the sensor back and it left at least another mm of pad material exposed.
So what causes pads to wear so unevenly between wheels and within a single calliper?