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I have had a few tubes fail flat in the middle of a ride, even when they were fully inflated at the beginning. When that happens, and the tube isn't punctured, I re-inflate them, but change to new ones as soon as I get home.

Is that a sensible approach? When I inflate them outside of the wheel, there is no sign of damage, or bulge. How much should I trust a tube that has failed me? Right now, they are in the purgatory box for emergencies.

It has happened with both Presta and Schrader valves.

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  • A leaky valve might hold the pressure when testing for a puncture as it is on a couple of PSI. Mount the tube and inflate to tires maximum PSA then check valve.
    – mattnz
    Nov 4, 2022 at 0:29

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If the tube looses air, then its coming out somehow.

Check your tube for a hole by inflating it to about 2~5 PSI outside of the tyre, and if the hissing of air isn't heard then submerge it in a tub/sink of water. The air bubbles show where you need to patch.

If the tubes all have holes in the same place relative to the valve, then look at your rim/tyre and find the cause.

It is not uncommon for a small fragment of glass or wire to hide inside the rubber of the tyre and repeatedly puncture the tube, and then retreat into the rubber when you're not riding. Inverting the tyre can help, and work under bright light.

If you can't find a hole, check the valve. They can sometimes leak slowly, but the water-test will show that.


If you're disposing of tubes, then that's wasteful. A patch costs somewhere between 20c and $1 (roughly) and a tube costs $4 to $20.

Patch a $10 tube twice and you have saved yourself about $18.

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    That is what I meant that I tested them. Re-inflating them on the field, and back at home they seem fine. It has never happened on the same wheel twice. Weird thing is, the deflating seems rather sudden, for example once it went from fully inflated when starting, to flat after a rough patch, in about half an hour.
    – Davidmh
    Nov 3, 2022 at 12:25
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    @Davidmh there are odd flats where there is a puncture but it doesn't show up easily. I've had a few that need unusually generous inflation to show bubbles, for example
    – Chris H
    Nov 3, 2022 at 16:29

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