I switched out the 17s for the Nismo wheels. The steering wheel shimmies (left to right) a bit after 40mph. I got an alignment done, but the prob is still there.
Is it possible that the tires and wheels are not balanced correctly? Any suggestions? I got the tires mounted to the wheels at some small independent shop, and got the alignment done at the dealer. Who should I contact? Thanks for your help.

 

Get the tires balanced!

 

Tires are not balanced properly