Rear Brake / Caliper Issue
I have an issue but I am not 100 % sure what it is or what is causing it. Leaving work the other day I rolled my windows down because it was a nice out. I drive past the wall and garages, I hear this slow scraping sound (10-20 mph) reflecting off the wall about 3-5 feet away. Since then noticed the sound it has continually happened at those slow speeds and when the sound is able to reflect off of something. So, I stick my head out of the window and I determined that it is coming from the rear (drivers side). When doing the same test for the passenger side, I hear nothing.
I take the wheel off, inspect the rotor, caliper, and pads (as best as I can without taking them apart) No visible damage found. They look identical to the passenger side.
I hear no noise in the cabin while driving with the windows up, radio off, and back seats down at any speed. With my head sticking out the window I can only hear the sound while having something close enough for the sound to reflect back to me and seems to go away over 30 mph (or maybe the wind noise gets too loud) I don't feel any brake pulsing BUT during a hard braking test - it felt like the rears locked up slightly under heavy braking, though, I am not sure if this is normal or not.
Any ideas what this might be? I am still under my 3 year / 36, 000 mile warranty - but I thought I read something that consumable problems (i.e. brakes) were not covered.