The Schwalbe 27.5 SV21 inner tubes I had on the rim are quite flabby; they do not hug the rim by any means, though they have worked out OK with Schwalbe Marathon Cross tires I had. But I wanted to try out a Panaracer GravelKing 650B tire 27.5x1.5 (38-584). I really struggled trying get the tire onto the rim and in the process pinched the tube. Are there skinny presta inner tubes available (in the US) for 650b?

  • 2
    I know for a fact that there are at very least 27.5 x 1.50 tubes. Which is the same ISO as 650B so you may include them in your search as well.
    – Nate W
    Commented Jun 27, 2023 at 22:41
  • Is it the elasticity of the elastomer compound or the amount of it that allows the stretch to accommodate multiple tire width sizes, like a sock that fits sizes 6-12?
    – Tim
    Commented Jun 27, 2023 at 22:59

2 Answers 2


You can also use a tube designed for 26" tires just fine. There are loads of those with Presta valves around.

I actually ride exactly that combo with 42-584 gravelkings and it works just fine.

  • Thanks. Maybe I will try that. I have some Schwalbe tubes marked 16"/18" that worked very well for a folding bike with an 18" rim and a skinny Kojak tire. The tube fit the 18" perfectly with no slop. My tire-mounting technique must need a lot of improvement since I've ruined two tubes now where the excess tube material is getting pinched as I try to get the tire onto the rim.
    – Tim
    Commented Jun 28, 2023 at 12:15
  • 1
    Try inflating the tube a little bit before you put it into the tire (like enough to give it some shape but not enough to make it rigid), it saved me from pinch flats many many times!
    – baks
    Commented Jun 28, 2023 at 13:00
  • Thanks @baks. I inflated to the point that it was a just barely a stiff circle and would hold the shape, but there were about two inches of daylight between the rim and the tube at the 3 o'clock position if I held the tube against the rim at the 9 o'clock position. That was no problem with the Marathon Cross tires (the tube could be tucked inside the tire) but didn't work at all with the GravelKing.
    – Tim
    Commented Jun 28, 2023 at 13:38
  • I found a Conti Tour 26 tube online that specified among other sizes those in the 37-584 > 44-590 range, and the tube fit the rim quite well when inflated a little, with no excess "flab" to get pinched.
    – Tim
    Commented Jun 28, 2023 at 19:13

27.5 x 1.5 is not a particularly uncommon tire size. Every manufacturer I would buy a tube from makes a suitable tube with a Presta valve.

The trick is using the correct search terms - "27.5x1.5 bicycle tube presta" or "650B x 1.5 tube presta". Using "Iso 584\ x1.5 is less useful.

  • The problem I'm running into is that the Schwalbe tube for 27.5 is hugely oversized, whereas the Panaracer tire is extremely difficult to seat on the rim. And the 650b tubes I'm finding online cover a very wide range of tire widths, so I imagine they will have just as much "slop" as the Schwalbe.
    – Tim
    Commented Jun 28, 2023 at 12:10

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