I have an '05 R52 S. I just recently started hearing a grinding/rubbing sound, so I checked the brake pads. All (visible) pads had a good amount of pad left, except the right rear which looked to be completely worn. This indicates a potential issue with the caliper, except I have noticed my DSC light coming on randomly. Mostly when I'm in corners or on a windy road, but I can't turn it off until I shut the car off. Would this potentially have something to do with it? Also, I haven't had any brake wear sensor lights come on.

 

In all probability, you have a sticking piston in that caliper and it's not retracting as it should. If the pad is worn down close to the backing plate, the sensor should've worked...unless it's been disconnected or dislodged.

 

Since its the rear brake it could also be a stuck parking brake mechanism inside the caliper. Living in the rust belt I've had to change rear brake calipers in all my cars over the years because the parking brake mechanism in the caliper seizes due to corrosion.

If just one of the two pads is worn it could also be the caliper guide pins that are binding. When you replace the brake pads take the rubber guide pin boots out of the caliper bracket and check for a build up of corrosion in the hole. My son had an R50 and we cleaned those holes about once a year because they would get a strange white build up of corrosion. Again, this was in the rust belt so your mileage may vary if your not.

 

The other possibility is a wheel bearing is starting to fail