Yes, I carry a spare tire. A couple of years ago while coming down a hill I encountered what must have been a piece of bent metal which made a nasty slice through the sidewall just below the bead down into the tread - over 3" long. I couldn't make an effective boot with a Park stick-on boot, a dollar bill (not even a $20!), or anything else I had with me. It was a very slow, uncomfortable ride back, trying to baby the rear tire - I finally got a semi-working tire from multiple tube patches and a dollar bill that stuck out between the bead and rim. Ever since, on any ride that takes me out and away, I carry a spare folding tire. Dead weight? Maybe, but it's cheap insurance.