I'm completely stumped... the car drives great but after about 10 miles or so the car will start to vibrate. It feels sortof like it one of those grocery carts with that one wheel that shakes. It isn't at any certain speed. Matter of fact I can freely hit 70+ when the car is warming up comfortably. It's just later it is so bad I'm scared to go over 15-20. It does seem to feel worse as I'm braking to stop the car. Anyone have a similar situation before?