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1. First, loosen your lug nuts for the corner you are working on, jack the vehicle up and put it on a jack stand, then remove the wheel.
2. You now need to dislocate the caliper. There are two 14mm bolts that need to be removed: A lower one, and an upper one. Once removed you can wiggle the caliper back off the rotor, and lay it up on top of the rotor next to the strut.
At this point, DO NOT let anyone touch the brake pedal.
Here is the lower retaining bolt location.
Here is the caliper dislocated.
3. At this point you can pull the pads free. I just carefully wedged my finger between the rotor and the pad to lever them free. They locate/remove in a manner perpendicular to the axis of the rotor. There are two of them on each side; remove them both.
You will note that the inside pad has a metal 'clip' attached to it. The purpose of this is actually to rub against the rotor when the pad material is getting worn low; thus creating the horrid metallic squeal that will remind you your brakes need attention.
4. Organize the new parts. There are two pads, each with one plastic-coated plate, and one shiny metallic plate, and one metal clip. Subaru also provide some brake grease for you.
5. Remove the old clips by just dislodging them with your fingers.
6. Grease the new clips on the surface that mates to the caliper mount, and locate them in their respective positions. The two clips are identical and interchangeable.
The new clips located in position.
7. Liberally grease the back of each brake pad. Be very careful not to get grease on any braking surface. Once greased, clip the plastic-backed plate into place on the back of the pad. Put a smear of grease across the center of this plate, then clip the shiny plate into place over the plastic-coated plate.
The black plastic-coated plate clipped onto the pad.
The shiny plate clipped over the black plastic-coated plate.
8. Now locate the two fully-assembled pads into their respective positions, making sure they are held securely in place by the two retaining clips. Again be careful not to get grease on any of the braking surfaces.
9. It is now time to replace the caliper. If your old pads were badly worn as mine were, you will now notice that the caliper pistons are too far extended to allow you to relocate the caliper.
At this point, remove the cap from the brake reservoir. Now you are going to depress both pistons. To do this I used the lug wrench lain across the two pistons, and pushed on it with both hands. I made a rocking motion from one piston to the other until eventually they were both fully depressed. You can brace the caliper against the strut so that you can get a decent amount of force onto the caliper. While you are doing this, it is important to periodically check the level of the brake fluid in the cylinder. Brake fluid is extremely corrosive and is the best paint remover there is - you don't wan't it splashed around in your engine bay.
If you cannot get the pistons depressed, you will need to release pressure (and fluid) from the system by opening the caliper bleed screw (with a hose attached and appropriate catch can ready). This will allow you to easily depress both pistons, BUT will absolutely necessitate a bleed of the brake system afterward. You may also have to follow this procedure if depressing the pistons causes the reservoir fluid level to get too high and you do not feel comfortable trying to soak up the excess with a paper towel (CARE NOT TO DRIP BRAKE FLUID ON THE PAINTWORK).
Once the pistons are fully depressed, relocate the caliper and replace the two bolts.
10. Well done. You are home and dry. Replace the tire, and lower the vehicle from the jack stand. Torque the lug nuts to the specified values.
Repeat for the other side (do one side at a time).