If you are changing brake discs, you may find my guide here useful.
Changing front brake pads has got to be one of the simplest maintenance jobs to carry out on the S14/a/S15! It is actually easier than an oil change.
Take a look at Figure 1 and familiarise yourself with the construction of the calliper.
After removing the wheel, the first thing to do is remove the pin clip from the rear of the calliper. this allows the calliper pins to slid out. The best way to do this is to push your thumb down on the top half of the cross spring applying pressure to the tops of the pads, and slide the top pin out. Just sliding the pin out will send the cross spring into orbit once released! You can then slide the bottom pin out easily.
Remove the cap from the brake fluid reservoir in the engine bay to allow for the increase in fluid once the calliper pistons are pushed back. The easiest way to push the pistons back is to keep the old pads in place and use a flathead screwdriver to gently lever the pads away from the disks. Remember to put a cloth around the screwdriver to avoid damage to the disk! Once you have a small gap between pad and disk, you increase the leverage.
All four pistons need to be pushed right back as far as they will go (don't force them!). You will now be able to freely slide the pads out of the calliper (Figure 2). Take careful note of how the pad retainers and shims fit on the pads - you're going to have to put them on the new pads!
Figure 3 shows all of the parts removed.
OK, time to put fit the new pads. Place the shim and retainer on each pad and gentle slide them into place. Don't push them in too far! The top edge on the pad should match the groove on the outside edge of the disk. If you're fitting new disks, compare the position on your old disks.
Fit the cross spring onto the bottom pin and slide the pin back into the calliper. The pin should go through the pad holes. Push the top half of the cross spring down and slide the top pin into position. You can now fit the pin clip back into the pins. The clip should be flush with the wall of the calliper, not loose. Centralise the cross spring if necessary.
Gentle press the brake pedal until you meet resistance to position the pads against the disks.
That's it! Do the other side and you're done. Make sure you check the brake fluid level in the reservoir and replace the cap.
DON'T FORGET!! You need to bed the pads in. No heavy braking for about 200 miles!