I have a 2009 Mitsubishi Lancer. I was using winter tires of size 205/60R16 and changed into 215/45zR18 summer wheels yesterday by myself. Now when I drive on not-flat uneven or wavy roads , I can feel/see the steering wheel turning left and right. I didn't feel this before on the same roads with winter tires. I double checked for a loose lugnuts and they seem fine. Can someone help me? Thanks in advance.
Wider, lower profile tires have a tendency of following road deformities (i.e. ruts, ridges, etc) more so then narrower, higher profile tires. Not sure if this is what's happening in your case, but if the wheels lug nuts were torqued correctly and the vehicle suspension is in good shape, it is the most likely cause for what you are experiencing.