I recently had a flat and replaced the inner tube. It pumps up just fine, but then when I leave it and come back it's completely flat. I replaced the tube twice more, with the same result each time.
The the punctures were
- Just to the right of the valve on the rim-side, not a clean cut but a small hole as if the material had been stretched or twisted too far.
- Roughly opposite the valve, a 6 or 7 inch gash, not straight. I couldn't tell whether this was rim-side or tyre-side.
- Just to the left of the valve, rim-side, a clean hole about 5mm long.
- edit: replaced rim tape, put in new inner tube. 2 minutes later I hear it go pssshhh, same result as number 3.
- edit: added second new rimtape on top of first, new tube, 2 minutes, pssshhh, same result as number 4.
I'm using the process described in this video, except that I don't use a tyre lever to put the tyre back on after inserting the new tube (because I've previously made the mistake of pinching the inner tube and making a hole), instead I just use my thumbs to push the bead over the rim.
I've examined the inside of the tyre and the rim, I haven't found any aberrations (no spokes sticking through rim tape, no holes or foreign objects anywhere). Edit: chap in repair shop had a look at the tyre and confirmed it seems fine.
Could these different failures all be caused by the same thing?