Getting a BBBBBRRRRRR vibration at around 60-65 mph (2000 RPMs). Almost like when you're too far over the lane and hit those ridges to tell you you're going off the road. It happens for about a second or two and let off and upon accelerating again it will mostly reoccur. If RPMs are pushed up by sudden acceleration, it doesn't happen and transmission sounds smooth. so here's the thing, I brought it to the dealer since I took ownership only about 2 weeks ago and their prognosis was to rebalance the wheels and they said it didn't reoccur. My husband drove it to work via highways and hills (12-15 miles) and heard it again, but very quick and slight. Do you think this is something to do with the tires? 16 inch Continental-touring I believe. Or what else might it be? HELP!