I just installed some new 17" wheels with tires that were premounted on them

Now anytime I go past 55mph I'm getting some serious vibrations in the steering wheel on my LS model
At 70mph it gets worse, and at 90mph its tough to hold on to sometimes because the vibrations are moving the steering wheel a bit

I've checked tire pressure, lug nuts are tight, not sure what the issue is here. Any ideas?

 

I had the same problem with my 18s, I finally took them off. No shop could find out what was wrong with them, no bent wheel, tires were fine and in balance. My buddy put them on his Civic and had no problems with them, I can't figure out what was wrong.

 

quick internet search looks like it may be the wheels not being balanced properly, ill bring her to the dealer to get them rebalanced
if theres anything else i should try, let me know guys

 

If not the balancing.
Tires maybe out of round or not seated on the rim properly,you could try over inflating them to say 50 or 60 pound and then letting the air back out to 32 psi.
Are the rims drilled correctly for the cobalt hubs.
Another thing is to remove the shiny steel spring washer that holds the rotor on for factory install.
(Its pushed on to the stud to hold the rotor in place in the factory until the tires are installed
You dont need them anymore)
The new rims might not clear it and will be sitting against the hub unevenly.