# Complete beginner's question: inner tube too big?

My tire wall tells me that my tires are 26 x 1.95. I bought a 26 x 1.75-2.15 inner tube. When I change the inner tube, though, the tube is bigger than the wheel by two inches. How do I determine inner tube size? Or am I just doing this wrong?

• Bigger than the wheel by diameter? How are you measuring? By the way, the size printed on the box can differ from the size printed on the inner tube, the box sometimes lies. Jun 28, 2020 at 14:15

## 1 Answer

That tube should be the right size, based on the numbers.

If you inflate the inner tube outside of a tire it will generally balloon up quite a bit, becoming quite a bit bigger than the tire.

When installing a tire and tube you should generally just inflate the tube to the point that it "fills out" -- not really much more pressure than you could blow into it with your mouth. Then the tube should fit comfortably inside the tire.

If a tube is too big in overall diameter there is a danger that it will "telescope" inside the tire (similar to "intussusception" of your intestines), resulting in a lump and, eventually, a split in the tube. Having the tube inflated too much while installing it is one way you can get this situation. (The other is simply having a tube that's too large.)

• If I put the inner tube around the wheel completely uninflated, should it be snug-ish, then? Apr 10, 2013 at 22:33
• @BernardSoubry - Not necessarily snug, but no significant slack. Different tubes respond differently to being inflated -- some immediately get "longer" while others will at first "shrink" as they "fatten up" a bit. Apr 10, 2013 at 23:45
• The number on your tire is "wheel size" by tire width. The numbers on the tubes should "match". Tube sizes generally indicate wheel size by a range of tire widths they will fit. Oct 1, 2014 at 0:13