I've been monitoring this for a month now and yesterday it got worse. I checked my tire pressure at least once a week and the rear driver side is always low on air. Well, I neglected to check in the last two weeks except yesterday. I usyally have at least 35 psi all around and the rear driver side was 18 psi WTF!! I guess I picked up a nail somewhere or do you think it's a tire flaw? I'm bringing it in to my dealership tomorrow and have it checked. Is this covered by the warranty?