I recently bought a new set of tires and noticed not long after that my xterra was pulling slightly to the rigth hand side. So I took the truck to the dealer and they adjusted my alignment, however now when I go over 60 mph the truck begins to shake. I just noticed on my bill from the dealer that when they fixed the alignment they flipped my two front tires for no apparent reason. I am very annoyed by this and now have to go back to the dealer so they can find out why my truck now shakes when i go over 60. any ideas would be appreciated