Thanks Jack. At least now I know that the 15's will fit around the brakes.
I found a few decent rims on Craigslist over in the Denver area so I may be altering my criteria for Riff Raff. I'll have to wait and see what he comes up with. If we/he can find some decent snow/winter tires for the stock 18's then I would rather not spend the extra cash on rims, but if I can find winter tires for a 16" or 15" rim a lot cheaper then that would offset the cost of the rims.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless