Night time fake puncture fairy

[Stradageek]

Hi, apologies if this has been answered before but can anyone tell me the most likely cause of the following:

Check bike on the evening before a ride, all ok, pump tyres up to normal pressure, go to sleep.
Get up in the morning, mount bike to find a tyre has gone soft/flat.
Sigh, remove tyre, change inner tube (carefully checking tyre for cause of puncture - find nothing) enjoy nice ride
Come home inflate offending tube and fail to find anything wrong, even when checking imersed in water
Leave inflated for many days, no loss of pressure.
Post message for help on CTC forum

[Brucey]

some possibilities

- someone (fairies?... ) has tampered with your bike
- the presta valve locknut wasn't tight enough before and/or there was crud on the valve seating, so there was a leak.
- a patch has lifted from the tube and has sort of resealed itself again, having let the air out (this happens quite often BTW)
- the valve stem is coming away from the tube, and is strained differently outside of the tyre such that it seals well enough at low pressures, so that the tube doesn't show a leak right away when tested.

cheers

[thirdcrank]

Does anybody with a sense of humour have access to the bike? That cause is IME more likely at work than at home, of course.

[Gattonero]

Leak on the valve?
Sometimes the stem will bend slightly, if you tighten up the valve cap over it, it will force it straight and cause a very small leak.

Also check for "scars" on the inner tube, often caused by overlapping rim tape, burrs in the rim or valve hole, integrity of the tyre bead, etc.

[Cyril Haearn]

Does anybody with a sense of humour have access to the bike? That cause is IME more likely at work than at home, of course.

There is nothing humorous here, it happened to me once, I heard but did not see the crime
It was the children from next door

Bruceys answers seem plausible but I still believe in the leprechauns

[531colin]

https://forum.cyclinguk.org/viewtopic.php?f=5&t=88368&p=802273&hilit=puncture+puncture+puzzle#p802273

Might not answer the question, but it shows you are not alone!

[horizon]

Yes, I've experienced something similar and failed to find the leak when immersed in water. But we did discuss on here the Presta valve problem (internal washer? or catching the insert slightly at an angle?) and I wonder if that can be variable - sometimes you hit it right and sometimes you don't.

[ambodach]

Not on a bike but on my MGB on Calmac ferry. Down to the car deck and one tyre flat. Delay the ferry and about 60 cars plus countless foot passengers while wheel is changed. Straight to garage for repair who could find no leak and tyre remained up after reinflation. Valve cap was still on so perhaps tampered by a clever fairy.

[Stradageek]

Thanks guys, the valve theory makes most sense, I'll check more carefully next time

Thanks again

Stradageek

[MikeF]

I've had this happen - a tiny piece of wire stuck in the inner tube. It was almost self sealing, but not quite. If you have something like this stuck in the tyre it could be a cause of the problem.

[mjr]

I've had this happen - a tiny piece of wire stuck in the inner tube. It was almost self sealing, but not quite. If you have something like this stuck in the tyre it could be a cause of the problem.IMGP5294.JPG

I've had a bit of wire like that get between the internal puncture strip and external rubber on a tyre. After causing about 7 punctures in short order (within about 5 miles), the tyre had started to visibly delaminate and was junked.

My bet on the OP's problem would be an unusual valve fault, though.

[andrew_s]

The last time I had a similar mystery overnight deflation, it turned out to be the valve stem starting to come away from the tube

If it's a tiny normal puncture, something that leaks fast enough to go flat overnight will also give noticeable overnight deflation if the tube's pumped up to jumbo size outside the tyre (stretching to jumbo size also stretches the hole, offsetting the lower pressure).

[Stradageek]

Yay, cracked it.

Replaced the tube and the next tube did the same. On the second tube I found a tiny leak in the presta valve; the valve assembly wasn't screwed in quite tight enough. I went back to the original tube and found that the valve body was again just short of being screwed in tight.

It seems as if I have a batch of Schwalbe 406 tubes where the valve assemblies are just a fraction loose.

Mystery solved