Don't sweat it!! They're really looking for that you have a full size spare. I've been there several times, and know alot of the people that check for these things. They'll never look at the size of your tires. Now if you're running 36" Swampers, and only have a stock size spare...that's a problem. If by some chance something happens to one of your tires while on a trail, I can almost guarantee you someone will have a 31" spare to get you off the trail.