probably a very simple probblem

[2004GrandPrixGT1]

Hey guys, first time posting in the suspension area of the forums here. Hoo-ray! Well my most recent problem is on my 04 gp gt with stock suspension i had new 16 inch rims mounted on my tires and now the car shimmy shakes like a mofo around 60 and just gets worse from there. I went to walmart to have them mount the tires on the rims, and i paid for them to balance them, they have new tire weights on them but they dont feel balanced at all. My thought is that they need to be balanced, but this time not by walmart. Do you guru's have any insight on it?

[SlowNA06]

It's possible they damaged something under there. I've seen Sears put a lift arm through a control arm.
Make sure your lugnuts are tight.
Check to see if your alignment is obviously off.

Outside of that, I'd work on getting your money's worth and go back to Walmart and go for a ride with someone.

[2004GrandPrixGT1]

I didn't give them the car, I just took the four new rims with in the truck and had them mounted on the good years and nexen tires I have. No vibration before the new rims, now vibration like crazy at and above 60 mph.

[SlowNA06]

Warped rims?