Thanks for the info, really appreciate it.My wheels are 17x8, and a 245/45 sticks out a bit. Any narrower on the wheel and I think it wouldn't fit, or would bulge in the center. Look at specific tires and the specs will tell you what size wheel works for any particular tire size.
Tirerack says minimum 7.5" width for 245/45 in both Continental DWS 06 and Michelin PS4 all season. I haven't looked at all of the different tires available, but not even all the 235 width options I'm seeing are meant for a 7" wheel. Actually, the DWS 06 page shows the widest tire that will fit on a 7" is a 235/50, but that puts you at 26.3" diameter, and I think the stock size gives 25.4"
Look around, there might be something else out there, and Tirerack has all the size info.