Suddenly the other day I hear this slight grinding noise coming from the rear of the car. At first you would only hear it when you where driving once you hit the brakes it would go away. Now its all the time and I can hear the noise change (kind of gets a bit higher pitched) when I hit the brake. First I thought maybe its the metal tab rubbing the rotor telling me I need new pads, but I looked at my rotors (with the wheel on) this morning and it doest look like anything is rubbing. I would suspect that if that metal piece was rubbing the rotor it would start to leave a cut mark in the rotor. Any Ideas what it could be?

Thanks,

Steve