The two vibrations are...
1. "The Wiggle" when one of the front wheels hits a pothole and the chassis twists and shakes it off like a wet dog.
2. "The Hoppity Horse" when you go over uneven pavement like highway concrete and you bounce up and down in your seat ever so slightly like a little kid on his Hoppity Horse.
I prefer to think of these not as design problems but rather as built in entertainment.
