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Tire sizes - scratching my head

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Chilidawg

Look Ma, No Hands!
I want to replace the rubber on my 1978 Schwinn Twinn tandem. They are 26x1 3/8inch. I bought two new 26 inch tires and they are too small. What am I missing?
 
there are different bead diameters for 26 x 1 3/8", sounds like you need the 597:

 
I never realized how many oddball parts are on these bikes. I am missing a seatpost which is 20.7mm with 5/8 top. Finally found a place to order them that won’t cost me 2x the cost of the part to ship.
 
So what rims are on your Tandem? There are two Schwinn rims that will take a 26 x 1-3/8 tire, the S-6 and the S-5. On your existing tires there should be markings, get the sizing information and BSD if they're marked. Sometime tires will say for S-6 etc. I really can't see a big difference in a BSD of 7 mm in a tire size to where it will or will not fit. Having a clean rim around the bead makes a big difference when mounting new tires. Sometimes a lubricant is needed, I use Windex. On the cheap tires there's a better chance of the tire not being made to the correct size.
 
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checked the tire and there it is
1273737
 
I want to replace the rubber on my 1978 Schwinn Twinn tandem. They are 26x1 3/8inch. I bought two new 26 inch tires and they are too small. What am I missing?
The tire sizing attachment Rustjunkie/Mod supplied should help. Tires and rims and their sizes are a jungle. American ( early) tires are more standard, but once they get into the later 60's and above, it gets sketchy, and Canadian and British/European get crazier. Many of the old tire sizes are hard to find. Good luck, I think you have been helped by good folks, and I'll say, no better folks than Cabers.
 
I never realized how many oddball parts are on these bikes. I am missing a seatpost which is 20.7mm with 5/8 top. Finally found a place to order them that won’t cost me 2x the cost of the part to ship.
All part of the fun. Keeps us intense?
 
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