I was going to buy these 15x7 rally wheels (http://pittsburgh.craigslist.org/pts/966501325.html) as spares and was wondering if they would be adequate to have street slick mounted onto. If so, what would be the max tire size I could use?

I would keep looking, a 8" rim would be better for a street slick, because most street slicks are 60 series.

Dave

Thanks Dave. I'll keep looking. I'm not in a big hurry right now. I may just have to buy two new 8" wheels. I have a lead on four 15x7 Corvette rally wheels which I'll probably buy just because I need them (I currently have the stock 14" rally's)

A 255 is generally the widest recomended tire for a 7" wide wheel.