So, I just had my first problem with foss tubes.
A few nights ago I was woken by a sudden “wham” sound and hissing noise. The 36" foss tube had suddenly blown.
At first I thought it was the valve, because the that’s where the air was coming out from. But taking it apart I found this:
The extra layer of the rimtape ends have created a tension point. I really like the foss tubes; they may be puncture resistant, but they are not durable, it seems.
Today I fitted a 29" rubber tube on my 36’er; and a pain it was! But it rides well. I got 24 km/t on a short stretch, so it’s not holding me back. I’m looking forward to see how it holds up, as it only weights a little more than my foss tube.
I have a Foss tube on a 29er. It’s been completely issue free, till I replaced the tyre. I replaced the tyre, inflated, then had a small slow leak. So I repaired the leak. All ok. (I left it overnight to be sure). I put the tyre on again, reassembled the uni and then discovered I have a leak again. So annoying. I havent further repaired it as I find putting this tyre on and off a big effort
However, I’d guess that your tube was a little weak right at that seam at the valve and the pumping wiggled it a bit and it broke through there. I’m rarely successful patching near the valve stem. I use a new tube if I get a leak there. Other places can be patched, but the valve stem area is really troublesome.
And from more reading… you can repair a Foss tube with a cigarette lighter?
From an Ebay description
“Explosion Proof: The tube is made out of a highly polymerized un-vulcanized rubber composite. When punctured, the material forms an air-tight seal around the nail or glass, dramatically slowing or even stopping the leak, giving riders extra time to react. Ultralight Weight: With a density of only 0.88 g/cc,the tube is 30% lighter than standard tubes which can have densities up to 1.3 g/cc. Easily repairable: In the event of a puncture the tube can be easily sealed with a simple cigarette lighter or Foss glue less patch. Removable valve core: Valve extensions can be used. Environmentally Friendly: Made from modified thermoplastic elastomer compounds (TPE), it can be recycled thus minimizing waste and protecting the environment. Free rim tape: Comes with a free rim tape. Size: 26x1.35 - 1.75 Valve: Presta.”
They often fail at the valve, where you can’t do anything to fix them. Often it’s because when you inflate them, and wiggle the valve, it puts stress on it. And as they leak more than regular tubes, you do inflate them more often.
Only the clear ones can be patched with fire/heat, if I remember correctly. And even then, it’s not 100% guaranteed success.
For a 36", there are good butyl 29" alternatives out there. If you really want super light, Tubolito tubes are an option.