Tire & Wheel question

What is the largest tire/wheel combination that you could put on an IS 300? I'm actually more concerned with the width because I know people have used 19" wheels without a problem. I don't currently own an IS 300 but I'm thinking about purchasing one in the next few months. I currently have after market wheels (17x8 Mille Miglia M11-2) on my current car (1998 Dodge Intrepid ES). They are currently fitted with Michelin Pilot XGT Z4 tires (225/55-17). I guess I have multiple questions. Is this wheel/tire combination too wide for the IS 300? Also is the diameter different? How do you figure this out? I know I got my current combination from tirerack.com because I was told it would work well on my current car.

My idea is that I would use these for the winter time. I know they aren't snow tires and 17" wheels maybe aren't the best choice but it would probably be better then the standard summer tires that come with the IS 300. Not to mention it would look much better. I also have my original 16x7 alloys and 225/60-16 Goodyears that came with my car. Could these be used on the IS 300?

Sorry for such a long message but if anyone could offer any suggestions or help it would be appreciated.

[This message has been edited by TakeFlight (edited September 27, 2000).]