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I'm replacing the inner tube of old bicycle with tire code: 47-559 (26 x 1.75). I bought a new tube that has spec: 26*1.75 - 2.125 (47/57- 559).

However, the diameter of the new inner tube is too large, such that it can't fit (folded inside the tire). It is also obvious that the new inner tube has larger (in diameter) than the rim.

I've read the previous post and also https://sheldonbrown.com/tire-sizing.html#iso.

I thought that using the same ISO code (47-559), I would get the correct diameter, but it isn't.

Then I realized, there's a code 26 x 1.50 on the old inner tube.

Can anyone help me with this matter? Is this mean that I can't use the ISO code (47-559) for finding a replacement?

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    Usually inner tubes, when sold, are labeled with a range of sizes. I try to avoid inner tubes which are at their upper or lower limit compared to my tire size. – Daniel R Hicks Sep 27 at 14:12
  • Sounds like your old tube is actually too narrow for your tyre's width, though butyl rubber is stretchy. – Criggie Sep 27 at 18:46
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    @Criggie, I don't the history of the bike, since i got this bike from someone else (for free haha). Yeah… but now i think that the inner tube was wrong... although it works well previously (before it's broken). The diameter of the old inner tube really fit the rim, this confuses me. – tetukowski Sep 28 at 7:49
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A 26 * 1.75-2.125, 47/57-559 tube should be fine for a 26 x 1.75, 47-559 tire.

Tubes can appear to be a little floppy and oversized on a rim before inflation. Remember the tube expands radially inwards and well as outwards as its cross-section diameter increases as it is inflated. Try inflating the tube a little before inserting it between tire and rim - this helps prevents folds and twists.

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    Thank you @Argenti Apparatus, I've tried what you suggested. Although the inner tube seems larger than the rim. When i put it inside the tire, it's OK. I still want to check one more time for if there's any fold or twists. The old inner tube diameter really fits the rim, this confused me actually. Thank you for the very fast response! – tetukowski Sep 28 at 7:44

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