I had an experience while riding up to York the other week that made me question the wisdom of tubeless tyres. I came out of a cafe to find my tubeless rear tyre completely flat. I think it had been feeling a little soft before but nothing that indicated imminent flatness. So I had a look at it and there was no obvious puncture nor any sealant leaking anywhere. Pumped it up and it held for about two minutes. Still couldn't see any obvious cause. Pumped it up again and noticed that air seemed to be leaking from where the valve enters the rim, so I tightened the valve lock ring. That seemed to do the trick but I decided to cut short that day's ride just to be safe. Rode about half an hour to campsite, pitched, tea, shower. Then the tyre was going down again. This time, as I undid the valve cap, was when it happened; the valve core had got jammed into the cap. Cue instant deflation and the tyre unseated.
No way I'd be able to reseat it with just a frame-fitting pump, but luckily I had a tube. I removed as much sealant as I could (easy from the rim, more difficult from the tyre) noticing as I did so that it had formed a few solid lumps – presumably this is where it had sealed holes? Perhaps it wasn't necessary to remove the sealant but I wasn't sure how it would behave with a tube. Interestingly, as I inflated the tube it squeezed some of the remaining sealant out of otherwise invisible holes that no sealant had come out of while in tubeless mode.
The following day I had an experience that made me question the wisdom of tubes! I had a puncture while on a track just east of Leeds. It was easy to find the hole and identify and remove the object, a piece of glass. I take out my puncture kit. This particular kit is a few years old but the tube of glue is unopened. I pierce it and... nothing happens. I can't squeeze any glue out. It has somehow set solid inside the tube. I don't know how this is possible in an unopened tube but there it was.
Fortunately I had instant patches too. These have always worked well for me in the past but this time I had trouble getting one to stick. I don't know if this was because of the sealant that inevitably coated the tube or just because of wet sweaty hands (it was a hot humid day and I'd previously put disposable gloves on to take the wheel out – I find it easier to prevent my hands getting covered in chain dirt than to clean them afterwards). Eventually I got one to stick and that got me to York, where it was the Rally and I got two tubes for a fiver. But until then, it was the backup to the backup to the backup that saved me.
