Hi all, i have a weird (sometimes slight) metal scratching sound in possibly my rear left tire. It started off less noisy, like i was dragging a skinny piece of metal around. Now it sounds like a router cutting wood (only way less harsh) or a loud old HDD. I hear this sound whenever I'm moving, not just when I break. The sound is also loudest when I'm going slow, I don't ever hear it on the freeway. What's making this sound? If my explanation kind of sucks plz ask for more info...

 

I'd recommend pulling the left rear tire and looking for something like a stone lodged between the backing plate and the hub. Also check for worn brake pads as they have a noise indicator that could also be making the noise.