2000 s80 T6. when driving at highway speeds the car tends to vibrate and shake...as if the wheels aren't aligned or something. I had this problem before and it mostly went away when i had the wheels aligned but now it is back in full force. The tires are new. What possible things could be causing this problem? do i really need to have the wheels realigned every couple months? or could this be a problem related to the suspension...a bent sway bar or something?

 

One of the tires could be out of round. One could also have lost a wheel weight.

 

Agree with Tech, sounds like a tire isn't balanced. Have them balance the tires again.

 

I had the same problem and just got it fixed. It was the rubber cusions on the front springs. They had worn out, thus causing a vibration. While replacing those, found out that the shaft and cv joint was also bad. No vibs now.