This noise just developed in the past week, sounds like metal grinding around the back right wheel. Starts upon accelerating, less noise while turning. Loud enough to make people look when I drive by, at first I thought it was rocks in my wheel....but now sounds like, as someone on the forum said, "gravel grinding in the wheels." Having the town mechanic look at it, but can't get it to my Volvo guy until next week. Safe to drive?