How do you stretch a 29" tube?

Unicycles and Equipment
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I cannot set my Alchemist Rim + Vee tire using a 29er tube. I go on exploding it due to tire pinching the tube…
Before trashing another tube I need to know:
Can I inflate a Schwalbe SV19 inside the 36er tire without using the wheel? Will it inflate enlarging to a 36er size or will it just increase in air volume reducing its ID versus increasing its OD?

Last question… does anyone tried to CUT 2 TPU tubes and join them together? I’m in love with my rope spokes, but I need Revoloop tubes for every uni and they are not willing to help me building a 36er tube… so I’m considering doin it myself

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Can you describe how you are putting the tyre onto the rim, step by step process.
I had the same problem but with a nextie rim. I pinched 2 tubes whilst doing this

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Just inflate it?

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I think @bouin-bouin did some tests and the only one which really sustains stretching is the Michelin Butyl series.

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I’m using a stretched Schwalbe SV19 on a Nextie rim without issues. I used some flour (talcum powder might be better) to make the rubber slippery. I belive this makes the tube able to move and stretch more evenly inside the tire.
I think (it was a year ago…) that I just stretched the tube around the rim and made sure it was fairly evently stretched before I inflated it a bit (as I would do with any regular tube/tire mounting) to give it a bit of shape and then I mounted it inside the t-monster tire.

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I did stretch my SVB19 tube pretty easily on my Alchemist rim + Nightrider Lite tire. Put the bead of the tire inside the rim then insert the valve of the tube inside the hole of the rim as you would do on an usual set-up. Pump the tube outside the rim to let it stretch. Once it has the diameter of the rim, try to put it inside. Then deflate the tube so that it fits the rim. Then put the second bead in the rim. If it is hard, remember to put both beads into the center well.
Last but not least, when the tire is fully inside the rim, check the tube is not between the rim and the tire. If that’s the case, no worries! Use a plastic, non-sharped, lever to make the tire rest on the rim, not the tube. If it is hard, you can inflate a bit your tube. Voilà!

By the way, make sure the center wall is not fully covered by a too large rim tape. Otherwise, it will be really hard to set up.

I thought so before trying the SV19 tube. It is quite bigger than Michelin Butyl but it stretches pretty well… So good alternative if no Michelin tube available.

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You wrote that the tube outside the rim will reach the rim diameter… I will test it within a week! Thank you!

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I agree with Maxence, except that I don’t deflate the tube to avoid the risk of pinching it. But I only know the michelin butyl inner tubes. I prefer to say that I “inflate” the 29" tube, that to say I “stretch” it.

Here’s how I install a 29" tube in a 36" tire:

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Great video! You solved everything!

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Has anyone ever tried stretching a latex tube…?

I have a 29x 1.7-2.3” and a 700x29-38mm latex tube.

Considering giving it a shot after I build up my 36er.

It is supposed to be lower resistance than butyl and tpu tubes.

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I’ve never given it a try. Nevertheless, what I’ve read on the web leads me to think it should work better than butyl tubes.

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I don’t think people have had success stretching any latex tube to 36”. They tend to be glued together in a less robust way than the way butyl tubes are joined.

I stretch my butyl tube in the 36 tire off the rim overnight before mounting whenever possible. It relaxes back to a smaller diameter, but closer than when it started. If you’re struggling with pinching, as you start putting the air in you’ll want to carefully go around the wheel working the tube into position. Just put enough air to give the tube shape, too much and the tension will “lock in” the pinched tube