Yeah, sorry to say, but you should have bought some wheels equivalent to the stock 18" rims. I found some take offs here on the forum for an excellent price. They come up all the time. Maybe you can dump your "snow" rims and replace them with some 9.5" wide.
Your snow tires will still work on the wider rims. For track and autocross, you want wide, up to 10", to stabilize the sidewalls.