I looked for a thread describing how to install brake pads and couldn't find a detailed step by step description with photos. I did find a good post by Miles from the Tire Rack and used that, plus the service manual to do it. So I decided to document it more here. Please pardon this thread if this has already been done.
I wanted higher performance pads since I experienced pad fade after just a few mild laps at the track. The HPS is a good high performance street pad that will withstand the heat of a number of hard core successive stops.
1. Jack up the front of the car and pull the wheels off. I did the front pads, then the rears. Jack the front via the larger/further forward of the bars crossing under the motor. Keep the parking brake on to avoid rolling. Also, check that your fluid isn't too high. When you compress the pistons, fluid will move back into the reservoir, filling it up more.
2. For the front pads, remove the lower caliper bolt/pin. You can see it in this photo. Once the pin is out, pivot the caliper up and hold it in place with stiff wire or a bungie cord.
3. Pop the old pads out and... before putting the new pads in, spread some anti-squeak compound on the areas that the piston & slider fingers will touch. Here are the new and old pads and an STi pad just for fun.
4. You'll likely need to compress the piston some to fit the new pads in. Use a large C-Clamp with an old pad pushing against the piston as shown in the photo below. Then slide the pads into the spring pieces that you slid the old pads out of.
5. Be sure the pads are flush against the rotor and that the slider pin that you removed the bolt from is compressed a bit. The caliper should now pivot back in place. Secure with the bolt and torque to 25 ft-lbs.
6. Remount the front wheels and torque the lugs to 100 ft-lbs.
7. Now for the rear pads. Place chocks around the front tires and jack the rear of the car up via one of the aft lower A-Arm supports. Remove the wheels.
8. Pop off the front spring using a screwdriver at the spots circled.
9. Pop the plugs off the allen bolts/pins.
10. Unscrew the pins using a 7mm allen socket. You don't need to pull them all the way out, just out enough to pull the caliper free.
11. The pads practically fall out. Compress the piston, not by simply screwing it down with the C-Clamp, but by using a tool to screw the piston in. I used needle nose pliers, but there are proper tools for this. Apply pressure as you turn the piston. I found that clockwise worked. I also used the C-Clamp for just a tiny bit of compression as specified in the manual. 1mm.
12. Refitting the pads is a bit tricky since they want to fall out. With one hand holding the caliper use a finger or thumb to hold the inner pad (the one with the spring along the top edge) in place. At the same time, hold the outer pad in the frame against the rotor. The caliper should be be able to slide in place easily. Watch that the pins don't get in the way.
13. Torque the pins to 20 ft-lbs. and replace the plastic caps. Also work the outer spring back in place.
14. Remount the wheels, torque to 100 ft-lbs.
15. Before driving, pump the brakes slowly to seat all the pads. You don't want to not have brakes for the 1st couple pumps at the wrong moment.
Enjoy your performance pads!