Ford Repair: tires, 16 wheels, tire combo

Question
i just took off my 15in tires and put on 16in tires now the front end is shaking at 45mph or more can you tell me why?

Answer
Dario-

  I'm assuming you put on 16" wheels to go with the 16" tires.  If not then there's your problem right there.  But aside from that, any time you upsize your wheel/tire combo you should have the alignment redone.  My guess is that the alignment's off a bit.  Hope this helps.

Steve