they're close enough that the tubes are interchangable. The tubes I use fit 27x1 or 700x23

and I believe Panaracer still makes a 27x1 tire. I use them on my Schwinn LeTour and got a set new last summer. They're hard to find, maybe where I get them they are just backstock from long ago, but they're out there.


Another reason the wheels aren't compatible between old steel frames and modern 8/9/10 speeds is that the hubs on newer bikes are alot wider. That's why you have to bend the frame with a torch and a frame jig if you want to comvert your old steel frame to modern wheels.

so the tubes are bvasically interchangable, but the tires aren't and the new hubs won't work with old frames without some metalsmithing on the frame.