The very first step is verify that you have a 7mm allen wrench, it wasn’t part of my little allen wrench kit so I had to make a quick run to the local hardware store. While you are there you may want to also pick up some rubber gloves. As you know the stock brakes spread break dust everywhere. Once I had the right tool for the job replacing the pads was pretty easy.
The first (and possibly hardest) step was getting the car up on a jack and jack stand. Especially considering the BMW M roadster does not come with a jack. Once that small task was done and the wheel was removed the rest was fairly easy.
If you are working with the right rear wheel or the left front wheel there will be a brake sensor (blue arrow). This sensor is clipped into a notched out area of the brake pad. Get your fingers as close to the brake sensor as possible and wiggle-pull it free.
The next step is to remove the retaining spring. I used a few choice curse words to aid in its removal, you will want to squeeze and push in on the clip (red arrows) while lifting and pulling out on the back (yellow arrows).
On the back side of the brake, there are two plastic caps that cover the 7mm hex bit guide screws. The plastic caps can be pulled off with your hands, they are snapped into a rubber housing. Once the caps are out of your way use the 7mm allen wrench to remove the guide screws. The screws should be completely removed.
The only thing holding the brakes in place now is brakes themselves. If you are having trouble working the caliper free apply constant even pressure on the brake piston by pull on the outside of the brake (use caution – remember your car is up on a jack and jack stand). You are not going to be able to compress the piston with a single yank, just use medium sustained pressure and you will feel the piston loose pressure and release. It took me about 40 seconds of medium pressure for this to happen.
Once the caliper is removed, replace the inner and outer brake pad. The inner brake pad is clipped into the brake piston, pull straight out to remove.
The outer brake pad was just kind of stuck there. Note the sticky stuff on the stock outer brake pad, if the new pads you are installing do not have this you will probably want to take a look at my Stopping Brake Squeaks article.
Once you have the new pads in place, you may have to put some more pressure on the piston in order to reinstall the brake caliper since the new brake pads should be thicker than the worn ones you just removed. The rest of the installation is just retracing the steps you took to remove the caliper.
TWO VERY IMPORTANT NOTES: You will need to pump your brake pedal several times to get pressure back to the brakes. Use extra caution the first time you drive after replacing the pads.
When new, brake pads have a slightly rounded surface that ensures once broken in you get a maximum contact patch. But until they get fully broken in you are concentrating the friction to a smaller patch. This means that when brand new the friction/heat is in a smaller area so you should avoid overheating the rotors.