Hi Lewis,
So sorry you're experiencing such trouble; frustrating! A lot of work and concern, too, I am sure.
I agree with the others; first index the tire to the valve and rim, as suggested. I do it by placing the tire so the label is dead-center on the valve.. Once indexed, it should become clear where repeated puncture are occurring.
I also agree it is most likely a small piece of glass or sharp stone is the culprit. If it has not fully penetrated the casing or only gone partway through, it won't cause an immediate flat until the tube has been inflated awhile. I went through this on one seemingly endless commute that turned into one long tire changing session years ago; always indexed the tire, tube and rim thereafter. In my case, it was a tiny, sand-grain sized piece of sharpened gravel after an icy winter's day of road-sanding by the street maintenance crews. Like a tiny knife, it was. Another time, the nearly-invisible cause was a small piece of wire, part of the belt of a blown truck tire. This one was nearly invisible and really hard to locate. I had the hardest time removing it with pliers.
Here's a little laundry list of things to check:
- Inner tire casing (most likely cause, meaning the sharp piece has penetrated the tread and worked through; check the sidewall also). It helps to partially turn the tire wrongside-out when looking so the inner stands proud and any foreign objects are more visible. Careful running your fingers around; they can be easily cut like the tube.
- Rim tape (spoke end can be the cause here, as can the overlapping seam of the tape) A rim burr may not always be covered by the tape.
- Valve hole (a rim burr or sharp edge here can cause the valve to part when pumping)
- Bad valve seal in the tube (either a damaged presta bobble/nut or loose Schrader valve core)
- Tire liner (if present; these all seem to cause flats eventually as they wear the tube thin)
- Bad batch of tubes (porosity) or faulty patches (typically bad or dried glue)
Age can have something to do with it. New tires are generally more puncture-resistant due to the rubber being more "live". Tires of any type are more prone to puncture in wet conditions. I still recall science class in junior high...we used razor blades to cut and size tubing for the Bunsen burners. One could saw away all day with a dry razor blade, but add a drop of water and it went through in a single slice. Road hazards are more likely to do the same on a wet tire.
Hope this helps!
Best of luck,
Dan.
