If your car "tramlines" with 225's, it will be worse with wider tyres.
Your maximum width that you can run is limited by the width of the wheel, not the height.
I would think you could fit 245 tyres to your 18" wheels as I have 17x8 wheels and am running 235/45/17. The car also had an option to run 17x9 on the rear and use 255/40/17.
And whether they will then fit on your car and not rub it a whole different matter.
Personally, I'd say that 18" wheels on your car is a complete waste of time performance wise and will ony add to the price of your tyre bill.