Nor had I, until just now, as I was just riding along (well, heaving myself up a singletrack climb just on the edge of Reading)

The air didn’t stay in there for long.

Yep,

Happened to me in exactly the same way last year. Bimbling up a gentle climb and then sudden deflation, no impacts rock strikes etc. Spent a while trying to find the puncture before i suddenly noticed the valve.

I was as confused as you are now, can’t fathom how on earth it happens?

It went down so fast I thought I must have put a seriously big flint through the tyre. In fact that was the first thing I went looking for.

i had this happen.. turned out the tyre was slightly too big compared to the rim and slipped round when riding along.. which pulled the innertube with it..

the resulting leverage on the valve from the hole in the rim snapped the valve..

I can see how that’d happen… but in this case the valve was seated straight and still had the little collar bolt on it, screwed down firmishly to the rim. (ETA – and the snap was half a centimetre above)

Mine was like that too, almost looked as if the valve had been neatly hacksawed in half, with the collar bolt still fixed firmly to the valve.
Weird.

So where do you guys get your inner tubes from?

this happened to me yesterday with a brand new tyre and tube, thats why i’ve been searching the net wondering how this could happen. i was coming down a really steep rocky descent when all of a sudden psssst and it was flat, thought a rock must have snapped the valve but there was no damage to the spokes. mmm puzzled me

Tube slipping inside tyre, you need better/new gripper rim tape

…was seated straight and still had the little collar bolt on it, screwed down firmishly to the rim.

FWIW, generally a bad idea as any inner tube creep can rip the valve out. Use the lock nut to lock the valve cap on instead.

Tube slipping inside tyre, you need better/new gripper rim tape

Mine broke well above the rim

Tube slipping inside tyre, you need better/new gripper rim tape tubeless

Broke one the other week. Something pinged up into the wheel and then whoosh as the air came out.