I would have to agree with the above statements about your suspension. If your suspension (either shocks, springs, or both) are worn out, your car will have too much bounce when you hit a bump, or too much roll when you take a turn. Normally that tire size wouldn't cause any problems, especially on a car at stock ride height. Instead of getting spacers to correct the symptoms, I would check into new suspension to fix the problem.
I would also check the offset. If your wheels are sticking out too far, that will cause a problem, especially with a thicker tire like you have (compared to a 205/40/17). That is always something to take into consideration when choosing your tires. Good luck!