one of my weight Winne 29er friends runs 26 tubes in his 29er tires. he said they will stretch enough. I was considering this while i am still my riding my 69er until I finish my surly km. I always bring two tubes so i have been carrying two 26 and two 29.

talk to you all latter.
Clydesdale Paul Major Taylor Cycling Club San Diego.com

Sure they'll stretch enough but that doesn't mean it's a good idea.

People have been using 26" tubes in 29er tires for years, especially since 29er tubes were often unavailable in stores. Apparently they work fine.

My pops has been running 26 tubes in his 29er for years, works fine.

Yep, as a member of the mountain bike patrol, I carry only 26er tubes for both. I know others that have used 26ers for several years in their 29ers. Shouldn't be a problem.

I think I should temper that with a statement about how I'm not sure about some of the super light 26er tubes, but for standard "run in the bike store and pick whatever they have on the shelf" tubes, there shouldn't be a problem.

Why wouldn't you just use 700C tubes?

They're stupidly light, available everywhere, and even the correct diameter.

700c tubes are light enough as is, I wouldn't want to stretch them enough to get the correct pressure in a mountain bike tire...not when 29er tubes are now readily available at any bike shop. There's no need to rig something as simple as a tube for a 29er, just buy the right gear.

My guess is that, for a spare for a 69er, you could get away with either to just carry one tube. In general, though, I don't see a reason to use the wrong size when the right size is easy to find.

Put the 26" on in the ease of home, & carry a spare 29" tube..
Slipping the smaller tube over the bigger rim on trail can sometimes be a bother.

700c tubes don't stretch enough, unless perhaps you run too-high pressure, 26inch tubes do stretch enough, unless they are of the ultralight or whatever variety. Anyways, it sounds like the OP just wants to know if he can carry a single 26inch tube, and the answer is yes. That said I prefer 29er tubes. A little bit easier if you're in a hurry.

The problem with many 700c tubes is with their cross-section diameter. I've found some work, but most either split open along the seam, or failed at the valve stem where the extra rubber couldn't stretch enough to fill the tire.

But that said, I've never had a problem with 2.2-2.5" 26-inch tubes. They're great if you have bikes (or friends) with different wheel sizes.

I've never tried this so I'll have to take your word for it, but I see 700c tubes in 30c and 40c sizes that are pretty close to 29er diameters.

Watch out, the chance of catching the tube under the bead is much higher if you use a tube with insufficient external. It will become an excercise in "stuffing".

Having said that, it's better to use a 26x2.1"(ish) tube than a 700x32-40 (ish) tube. They stretch much better along the their length than in internal diameter. And ... you're risking bursting a seam which run along the length of the tube. Finally, you can actually "pre-stretch" a tube of smaller external diameter by over inflating it well over you're desired size. Leave it that way for a day or two, than deflate. The resulting tube will be easier to mount.