I had a great bike ride with friends on Sunday morning. With the clocks changing in favor of an early start we duly set off at 8am (yes, you crack-pots of dawners, that's early!). After about seven miles I got a flat rear tire. We found the puncture - a single pinprick hole - in the tube, but could not find a corresponding problem inside the tire or the wheel rim. We duly put it down to rubber fatigue, put in the (only) spare tube, pumped up, and headed on. Three miles later I had a flat again, and with the same pinprick hole at the same position in the tire (relative to the valve). This time a group of us all searched for the cause - and could not find anything. We took the tire off completely, turned it inside out and looked at it under the glare of the beautiful fall sunlight. Nothing. Again we searched, and the wheel rim as well. Nothing.
Meanwhile I was also working with my trusty patch kit to repair the hole. We decided to replace the tube and hope for the best ... what was the alternative?
As I reseated the tube inside the tire, when I got to the patch on the tube, I noticed a small bump on the outside of the tire. It looked like a minor imperfection caused by wear, but I tried to rub it off, and in doing so flicked out a very small grain of glass. This was the size of the period at the end of this sentence. It was lodged on the outside of the tire, and must have been impinging through the inner wall onto the tube under pressure. Without the pressure (whether from the tube inflation or the weight on the road) it did not poke into the inside of the tire which is why we could neither see it nor feel it inside.
Happy we had found and solved the problem I finished refitting the tube. We used a $1 bill (thanks Sammy) as shield for extra protection for the patched tube inside the tire where the glass had been "just in case", and went on to enjoy the rest of the ride without incident. Thanks to the early start we arrived home at the normal time, rather than significantly late. As I look back on this ride I have the same warm feelings of enjoyment of the ride, the company, the wind and the sun as I have for most Sunday rides. Puncture? Two punctures? Nooo problem.
There is a lesson here ... probably some pithy version of "be more thorough looking for the cause the first time!" Another lesson is "enjoy". It is not about arriving, it's about travelling hopefully.