I got a rear-tyre blowout recently using Conti GP5000S TR - near-slick tyre. Whilst I typically use these tubeless I had recently had a puncture and had to insert an inner-tube temporarily which I hadn't got around to replacing. After the blowout the tyre was irreparable as it had a 5mm tear on the tread, but when checking the inner tube my friend noticed that there was a sizeable stone inside the inner tube. I've tried to figure out how the hell the stone got in there!! The hole in the tyre was too small for the stone to pass through from the road. Even if it had, then it would've had to puncture the tyre, then the tube, and then insert itself into the tube fully within a split second.

I don't understand the physics of how that could be possible on a rotating wheel. Nothing stacks up for me. The best I can think of is that the stone was in there from manufacturing; but how the hell didn't I notice it when inserting the inner tube? I guess it's possible.

(The stone is shown in the photo)

Any ideas?

enter image description here

  • 5
    Any chance your friend could have secretly inserted the stone while checking the tube to play a trick on you?
    – TooTea
    Commented Aug 16, 2023 at 9:49

2 Answers 2


If the stone was inside a tube, it got there through a hole. You would have noticed it when installing the tube originally if it came pre-installed. Tubes come deflated, it would have been clearly noticeable like a snake after eating a large meal.

Rubber tubes are extremely stretchy, especially if the stone was the cause of the puncture in the first place. You'll have a similar hole in the tyre in the same place.

The other possible option is that if the tube had a latex sealant inside which has aged and balled up producing a lump, but that wouldn't look much like your example.


That stone looks fairly sharp-edged. Potentially sharp enough to perferate a thin (possibly worn?) tyre and tube if it chanced to contact the tyre edge-upwards. Possibly it perferated the tyre and tube (causing the blow-out) and ended up right inside the tube.

I once had a sudden puncture in a tubed road-bike tyre (tyre pressure about 100 psi before puncture). I found a hole in the tube but there was no obvious damage to the tyre. I had no spare, so I patched the tube, and was half-way through re-installiing it in the tyre when I felt something rattling about inside the tube. There was a 3" (75 mm) nail completely inside the tube. I had to re-puncture the tube to extrtact the nail and re-repair it in order to get home. Not quite the same as your experience, but proof that a large sharp object can end up completely inside a tube.

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