Stretching a 29" to fit a 36'er - How Big?

[One Wheel Good]

How big should I inflate the inner tube to stretch it so that it goes into the my 36'er. At the moment it's at about 38".

[SinisterJay]

the wheel size is usually measured by the tire diameter. I'd say if the outside diameter is 36", it should be fine.

[davidp]

Getting the tube/tire mounted is a bit of a chore but I was able to do use a generic 29x2.3" tube without pre-stretching. After getting the tube and tire on the rim I was very careful to work out any places where the tube was caught between the tire and rim while adding air very slowly. Basically I'd do 2-3 pumps then squeeze the tire and try to look between the tire and rim and see if it was clear, massaging out any places where the tube was caught by pressing the sidewalls of the tire together and bouncing the wheel.

[wdmunicyclist]

I tried this - it didn't work for me. The 36er tube is worth buying just to avoid a blowout while you are far from home.

[Nurse Ben]

It's a pita using smaller diameter tubes, way to easy to get a pinch, flatting at speed on 36er could be dangerous, I'd just do the 36er tube for safety.

How about a ghetto tubeless set up using a 29er tube on your 36er?

It's my next project, should be interesting

[redwelly]

As long as it looks about as big as a 36" wheel I wouldn't bother measuring it.

There is a lengthy guide to mounting 29er tubes on 36" rims around somewhere, but all you really need to know is:

• Pre-stretch the tube - over-inflate it to about 36" size (you've done this).
• Put a bit of air in it once it's on the rim (to make sure it ends up *between* the two tyre beads and not trapped flat underneath them).
• Use liquid soap on the inside of the tyre beads (again, to make sure they sit properly down in-between the tube and the rim walls; though it also helps ease the bead on to tight rims)
• Be really careful with your tyre levers - they must only be hooked onto the rim and not be pinching the tube inside.
• Inflate gently - check that the tyre is well seated all around the rim before trying to get to riding pressure.

It's not foolproof, so you may still pinch and need to go for a backup tube which will sometimes be needed.

It seems that 29er tubes in 36" wheels make them more susceptible to blowouts. The higher your pressure, the more risk there is.

Good luck

Sam