I'm planning on buying an S-line, which of course has the 19" wheels with summer tires. I already have a set of near-new winter tires that would be a shame not to use, but they're 245/45-17 size.

My question is, "What size wheel should I buy to use these winter tires on the new car?"

I know they need to be 17" diameter, and probably 7.5" or 8" width (correct?), but I'm unfamiliar with offsets or other criteria.

Thanks.