bah, it will work fine.
Ive also heard of people using 20" tubes in 24" rims cos they are lighter.
I used to put two 20x1.75 TYRES on one wheel and cram a 20x1.75 tube in there and it was always fine.
If you inflate an innter tube outside the tyre they go massive. It will take, just get it in there and pump it up.
multiple tyres?
you used to ride with two tyres on one wheel?
how would that work?
Yep, 2 tyres on one wheel ..... No, it didnt work that well! ha ha.
It helped stop pinch flats, but also most tyres had crap sidewalls and a few grinds would soon expose the tube.
If the inner tyre was knobbly then there were little pockets that would never get to pressure. This meant that even with a very high pressure in the tube, the bike still rode like it had flat tyres. Add that to the amount the bikes weighed in the 90s!
It worked better with a worn out inner tyre, and also it helped if you cut off the bead from the inside one.
Things got much better when Primo came out with the V-monsters, a tyre that was tuff enough to use just the one.
The other week I took some araya aeros off a bike that had been untouched for a few years. The front tyre came off easy, like they usually do on aero rims. The rear one took a bit more to get it off, and it turned out that there were 2 tyres on the rear. The inside one was a totally usable Blue Tioga Comp4.
