What causes this level of uneven brake pad wear?

[brettski]

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?

[rivroshaun951]

I am not a professional. This is just my opinion. I could be wrong.

Well the first obvious thing I see is that you did not mention anything about the condition of your rotors. If you did not machine your rotors then your pads are going to wear uneven from the beggining. Here is a list of possible causes.

#1. not machining your rotors after a pad slap.
#2. Warped rotors.
#3. to much wheel bearing endplay.
#4. Frozen brake caliper.
#5. Clogged brake line or a leaky caliper piston.

These are multiple reasons. But again since you did not mention anything about mating your rotors to the new pads. I would go with that first. Check the condition of your rotors. Don't just look at them. Do some measurements and compare them to spec.

[Jack Dabsy]

... Caliper slide pins, these should be replaced relatively often as they stick too, especially if they're slightly bent !