One of four rotors is rusty

[professor]

I supose it is possible that an accident resulted in a bent hub assembly, or a bent bracket. It is also possible that your top slider pin is bent, but I would think the bottom pin would thread in only with difficulty if that were the case.

I'd try swapping the bracket for the 5 minute solution, a hit to the wheel could easily bend that and it would be very hard to see. Still I would think application of the brakes would force the pads into contact, you can actually wiggle the caliper and bracket a bit by hand, its not really that stiff, its the pressure that holds things square more than any precise alignment.

[jmaziarz]

I took pictures of my old and new rear rotors for comparison. Larger versions of each of these pictures can be found here.

Side-by-side comparison of the old rear rotors. Notice the outboard side of the one on the left (this is the problem I have been trying to fix):



New rear-left rotor (again, this is the problem I mentioned about the new pads only touching the new rotor ~50%):



New rear-right rotor (looks fine):

[Legacy777]

If you've replaced the calipers, and still get the same results, you probably have a bent backing plate.

I'd suspect that over the spindle, because if the whole spindle was bent the rotor would probably be skewed the same amount as the backing plate.

[jmaziarz]

If you've replaced the calipers, and still get the same results, you probably have a bent backing plate.

Due in part to the cold and the mounting frustration I have with my ability (more like inability) to fix this car I have left it alone for the past few months.

It is interesting you mention the backing plate because while I was replacing the rotor I noticed that the backing plate was severely corroded. I tried using a wire brush to clean off some of the built up rust and huge bits flaked right off. In some areas, it is completely cracked or there is a developing hole from my handy brush work.

I have since brought the car to my local dealer and also a certified Subaru mechanic "friend". Neither found anything out of the ordinary (not shocking) but charged $50 for their time.

[Legacy777]

You might want to see about picking up a used rear hub at a junkyard and see if that fixes the problem.

[jmaziarz]

Problem solved.

I replaced the bracket that holds the pads and the entire surface of the pad now makes contact with the rotor. Ordered a new set of pads and will resurface the rotors.

Thanks everyone for your input and Blackbart for the bracket!