Two of my friends noticed while driving behind and beside me that my wheels in the rear of the car looked funny, like it was warped or something.

If I came from a 245/45/18(stock) to a 285/30/18 tire, do I need to get my cambers adjusted or something?

 

Depends how low your car is and how aggressive your wheels are. The short answer is yes, changing tires and wheels to a more aggressive size change the contact patch, and change the physical alignment of the car. How dramatic that change is is something only you can check on an alignment rack before and after

 

How wide are your wheels?

 

You have no business putting a 285/30/18 on the Z. That would look simply awful.