I have a knocking noise coming from my rear passenger side wheel area. Almost sounds like a rock kicking around. It speeds up as I accelerate and goes away as soon as I apply the brakes. It is starting to make a grinding noise for the first second I have the brakes applied. A similar noise occurred a couple weeks ago but only while I was turning and went away after a mile or so. Both instances occurred in the morning after a light snow fall and below freezing temperatures. Any ideas?