Why would a 2002 Hyundai Elantra give a grinding sound when you apply the brakes?

I've found the brake rotors to be made of some pretty flimsy metal. they wear down quickly and become severly groved no matter how often you replace the pads. i would suggest replacing the rotors and pads. Use an upgraded rotor if possible. I had the same issue, you have to replace both the rotor and the pads. Also, the pads have a vertical gap running through them, when replacing my old ones, I noticed that there is a tendency for a bunch of stuff to gather in there (could be part of the noise). In my issue, I actually had the pad wear completely off shortly after I started to hear that sound, then it was metal on metal... The 1997 Elantra I have has noisy brakes too. I asked about it at the dealership. The guy told me that it's just "dirty brakes". Every two weeks or so I rinse them out using a garden hose. It has stopped the noise. -Just a note, if you are doing something like this make sure you have not driven the car within 30 minutes to an hour, if you spray water on the rotors while they are still hot, they will become more brittle.