Tire Ratios
 

My new Civic has 16" (205/55R/16) aluminum wheels so I think i'm going to
get some winter rims and tires for it for the comming winter.

I was wondering if I could use 15" wheels & tires instead? If so, what size
tire should I get to keep the right ratio? Anyone know how I can find out?
16 inch low profile winter tires, which would fit right, are just too
expensive really and there's no need for such tires for the winter.