Fix that grinding noise in your brakes.

If your brakes make an alarming grinding noise, you can fix this up in a few minutes. Release the brakes by unhooking the “noodle” or in a road bike, by lifting the lever.
Remove the wheel to gain access to the brake pads. Grab a file, or a wood rasp or even some coarse sandpaper. A few rubs will remove most of the embedded debris causing the noise. You may need to pick out some bits using a pointy tool of some sort.

Then just replace the wheel in the normal fashion. Give it a test, the noise has gone!