The new 26" MTB inner tube is much bigger than my 26" wheel (and old 26" MTB inner tube). I don't understand why. How to shopcorrectly for new tube?

The bike is 1990s Raleigh mountain bike.

Edit: the new tube is very loose both deflated and inflated. The new tube specs are 26 x 1.5 / 1.75 / 2.125 F/V according to the box and tyre

The old tube was 26 x 1.50 / 2.25 according to its box.

enter image description here

  • It's not clear -- how much have you inflated the tube? With it uninflated (laying limp) is should fit inside the tire without "bunching up" -- it's normal for it to expand a bit when inflated, and the tire prevents that. (The image above looks close to "normal" for a tube that's been a bit over-inflated.) But as Mike suggests there are (at least) two different standards for so-called 26" tires. Commented Jan 7, 2013 at 22:30
  • What numbers are on the side of the tire? Commented Jan 7, 2013 at 22:57
  • (And understand, as Mike says, that 26 x 1.5 is NOT the same as 26 x 1-1/2.) Commented Jan 7, 2013 at 22:58

3 Answers 3


Check the label on the tube - does it say '26 x 1 3/8' by any chance? If so, this is actually a completely different size than the standard MTB 26". Get a tube that says something like 26x2.1 or 26x1.9 - the point is, the tire width should be expressed as a decimal, not a fraction. See Sheldon Brown's tire size chart.

Yeah, I know, it's stupid - I didn't come up with this system.

  • 1
    +1 I've been buying tubes for 15 years and I did not know that.
    – cmannett85
    Commented Jan 8, 2013 at 9:18
  • the ISO size of a real MTB tyre is 559mm andthe one in the picture is the old touring size of 26 x 1 1/2 is 584mm (which is making a comeback as a 650b mtb size) Commented Jan 8, 2013 at 12:46

You can essentially inflate the tube out as much as you want until it pops. If you over inflate it before mounting it, it wont fit. Try using less air. Generally, also, tubes are marked for a certain size of tires, so try to match that too (if the tube is too big of a size, you may have it fold over itself, while if its too small the tube may be effectively a bit thinner than you like, but there is some tolerance in this - one or two sizes either way from the tire probably won't make a difference provided you're using the right diameter and both the tire and tube are sold as fractions or decimals).


You might be better of if you compare ERTO-measures for your tires.

A 26 × 1 1/2 (= 26x1.5) is a 40 - 584 in ERTO, which is 40mm wide and 584mm in diameter. A 26 x 1,75 is ERTO 47 - 559 which is wider an has a smaller diameter.

Modern tubes tend to cover a wider range of tire sizes. Not everyone appreciates this. If the tube fits without folds it will do the job.


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