I don't have any out-of-town tours planned so I don't typically carry a spare tire, but do carry 1 (preferably 2) tubes. The exception is Bike Patrol duty for big events like El Tour, where I carry a spare light 26" street tire and a used folding 700 road tire, along with oodles of various tubes. I typically go through a bunch of the tubes helping others, and more often than will end up installing the 700c tire for a grateful rider somewhere along the route.