Classic & Vintage - 26"x2" MTB tubes in 26"x1-3/8" 3-speed tire?

Is there any reason not to use mtb tubes on a 3 speed?

I see both the MTB(556) size and Schwinn(590) 26" size stamped on the 26" tubes I have.

As long as it is not so big that it is wrinkled when you install it, I would do it. I would stick with the smaller MTB tubes if given a choice.

And, to be honest, I am not sure that wrinkled would even be a problem, as long as you didn't pinch part of the tube with the tire bead.

I wouldn't recommend it. The tube is gonna have to stretch quite a bit in order to fit, it would probably be somewhat difficult to get the tire on the rim and not only that I'd be somewhat worried about flats while riding too cause of the extra stress on the tube, not something you wanna constantly have in the back of your mind. Why would you want to do this anyway, don't wanna buy the tubes or having a hard time finding them? The only place ive found them for sale myself is in smaller hardware stores in the lil bike section of the isle!

Well I forgot to order tubes and have a bunch of mtb tubes, so I'm going to try it. Can always get some 1-3/8 tubes later.

I would try 26" x 1.25" tubes, not the 2.0"s.
I have an '86 Cannondale SM700 that has a 26" front wheel & a 24" rear wheel. I always carry a 24" tube as it will fit the 26" tire without "stressing" it too much.

The only place ive found them for sale myself is in smaller hardware stores in the lil bike section of the isle!

I hadn't thought of looking at wal-mart or western auto.....