Touring with spare 20” wheels
 

I would never consider bringing along a spare 26” or 700c wheel on a tour, but i'm guessing 20”ers wouldn't be too unwieldy to bungee over panniers. Yes they would be a pain to fly with because they wouldn't fit in the suitcase, and they are added weight, but think about the advantages:
1.Provided you have clearance for wide tires, you could have a main set with thinner, high pressure tires and a second pair with low pressure, wide tires if the road got rough or if you wanted to go off road for a day. It would be like making a 5 minute pit-stop.
2.If you had a flat or a broken spoke at a bad time, such as in the pouring rain, you could slap on the spare and ride until you found shelter to fix the problem.
3.If you bent or cracked a rim or damaged a hub somehow, you could keep on riding.

So, bad idea?

I tried it once for a 75 mile ride on a Downtube VIII in south america. I will never do it again, the cost-benefit was not appealing, at least to me. Spare tube, tire and spokes work way better.

I'd just make sure the rim widths were the same or very similar in size. Switching between Velocity Razors and Sun Rhynolites, for example, means you probably have to readjust your brake cables to accommodate the difference in widths. Spare tires and tubes are probably easier to carry, unless you're carrying an extra wheel with the same width rim.

So are you going to take both a front and a back wheel, then? ;)

Unless you're going to take both, and have the identical cassette on both the rear and rear-spare-wheel, I really can't imagine the benefit to this approach. And with two extra wheels with tires on them, that's a lot of extra weight and bulk. I personally wouldn't take a spare tire unless it's foldable....

My solution is Vredstein S-Licks, Spinskins, and a foldable spare tire. Big Apples would do as well, only the S-Licks were under $10 each. They handle as much off-road as I want with low psi, and roll really well with over-psi. The S-Licks are something like an 80/20 DOT enduro tire in the m/c world. If I'm planning on serious singletrack most of the ride, I would mount knobbies, Spinskins, and thorn-resistant tubes

http://www.bikepartsusa.com/view.asp...e&f_c2=20+inch

and bring two foldable slicks as spares. Not all knobbies are equal WRT punctures and flats, e.g., kiawe (mesquite) thorns. Flats on a day ride are bad enough. Flats loaded and touring seem more annoying.

If it were me, I'd want to travel as light as possible and wrench as little as needs be... since 20" wheel are inherently stronger, I'd build up a good set of 32 or 36 spoke wheels and mount my favorite indestructo Schwalbe Marathon Plus tires... they have gone places my Slime-liner equipped competitor tires failed miserably in (mostly thorn patches).. with tire pressure changes, they'll take you on or off road and be pretty acceptable at either ... then pack a foldable tire, tube, spokes and patch kit like the others have mentioned.

Bruce