Hyundai Repair: Elantra 2005 vibration, michelin mx, wheel alignment

Question
I bought new Elantra SE in June 2005 in a dealer at Mississauga. It is now about 63,000 KM. Since it was about 40,000 KM, I felt the car shakes/vibrate more on the highway (speed 110 km/h - 120 km/h). I tried to align my front wheels,  it was good for a while, and shakes/vibrate again. I have tried to align my wheel again at 45,000 KM, it was good for a while and shake/vibrate again. I aligned wheel again at 52,000 KM. It is still shaking/vibrating at that speed (110 km/h - 120 km/h). Tire is Michelin MX-4 and the treas still looks good. What should I check now? Should I change my Rotor? or Tire? or Wheel? Thank you.

Answer
If you haven't tried already, you should have your wheels and tires checked and balanced.  The symptoms you describe are typical of an out of balance wheel/tire assembly, a bent wheel, or a defective tire.  Wheel alignment is very rarely the cure for a vibration.