Originally Posted by DZeckhausen

There are several likely candidates for the scraping sound:

1. Your parking brake shoes are not centered and are rubbing on the inside of your rear rotors. (The 370Z uses a "drum-in-hat" parking brake design, where the rear rotors double as parking brake drums.)

2. Something is not right with the pads or the installation of them.

3. When you installed the rotors, you inadvertently bent the rotor dust shield, so it's scraping against the inboard side of the new rotors.

You can test these theories. The next time you start hearing the scraping sound, gently pull the parking brake lever to see if that changes or eliminates the sound. (Do this carefully and with your finger on the button, so you can release the parking brake quickly.) If it has no effect at all, then theory 1 is dis-proven.

Next, gently depress the brake pedal. If the sound stops when the brakes are applied, then reappears when they are released, there's something going on with the brake pads. Pulll them out and inspect for anything unusual. Like, did you install one backwards? (No insult intended - this is more common than you think!)

To see if it's the dust shield, you'll want to put the car up on a lift or jackstands and pull the left rear wheel. Then use a flashlight to see if you can see how much of a gap there is between the rotor and the dust shield. If it's really tight, use a couple of large screwdrivers or small pry bars to bend it back a little, making sure you're not simply moving the problem from one part of the dust shield to another.

Hope this helps!