Originally Posted by staehpj1

Don't rule out just using the same model tire you are riding on and use the method shown at: http://www.rideyourbike.com/tirefold.html

They fold fairly small and my cook set nests nicely inside of the folded tire so not much space is used. I carry it in the front pannier on the occasions that I carry a spare.

A folding spare could be nice, but I would rather carry a real touring tire if I carry a spare and good folding touring tires are not very available.

Usually I don't carry a spare though. If in a group I am more likely to carry one as part of the community gear since the extra weight is essentially shared between multiple riders by dividing all of the community gear equitably. We carried a spare maybe 1/3 of the time with three of us on a cross country tour. The spare was my front tire that I replaced during the tour when the rear tire wore out and I decided it was good enough to keep as a spare. It wound up replacing my daughters worn rear tire for the last part of the trip.

It was kind of nice to have a spare in the more desolate part of the country, but I can boot, sew, or otherwise patch a pretty badly damaged tire well enough to get to the next town and if all else fails someone will always give you a lift to the nearest town. So for touring in the US I normally don't bother with a spare.