I'm trying to get rims for my car.  The rims I want are 17 x 7, apparently.  I have the stock 245/45R17's on my car now.  Obviously they're 17", but 17 x what?  The guy who has my rims said that my tires are too big for the 17 x 7.  If that's so, what tire size would I have to have for them to fit?  Wouldn't I just go one size smaller?  Someone help me, please, this is so aggravating.