Halfway home, my rear tube exploded, for the 2nd time in a week, and I'm trying to work out what's causing it. Some history:
- Fri 26 Oct - less than halfway home from work, I get a puncture (not the exploding kind), and find that my rear tyre has 2 very deep holes in it, with bits of glass embedded, so I replace the tube and continue riding home;
- Mon 29 Oct - I replace the rear tyre with a spare one I'd bought previously;
- Sat 3 Nov - while still 100km from home on my long Lake Mountain ride, my rear tube literally explodes, and the tyre comes right off the rim, so again I replace the tube and continue riding home. I found no deep cuts in the tyre, so can't explain how the tube ended up with its roughly 15cm longitudinal split.
- Today - tube explodes again while I'm halfway home from work. Oddly enough, this time I heard a rattling noise for a few seconds prior to the loud bang the tube made when bursting, almost as if the tyre had actually unseated before the tube burst. I found one cut in the tyre (the same tyre I installed on Mon 29th Oct), but as far as I could tell, it only went down to the blue inner lining and no further. Also, the inside of the tyre opposite the cut was unmarked and appeared whole. This time, as well as inspecting every cm of the tyre, I also very carefully checked the rim tape and rim inner surfaces, and found no irregularities in either. I replace the tube and continue home.
So why 2 exploding tubes in a week? Some possibilities occurred to me:
- I've been inflating the tyre to its maximum rated pressure of 100psi, and no issues previously, but I'm wondering if perhaps it doesn't stay properly seated (at that pressure) on my current rims, which are the Dirtworks DT Swiss TK540 that I had installed almost exactly 3 months ago. Perhaps I need to consider running the rear tyre at about 90psi and the front at 95psi, or something like that? The shape of the rim isn't quite the same as the Velocity Dyads I had previously; hard to explain, but the rim edge, against which the bead of the tyre rests, appears a bit more curved.
- Could I have a dud tyre, with a bead that is too loose, and thus causes the tyre to easily unseat from a rim?
- Or perhaps I've been using dud tubes? The ones I've been using recently are the Tioga brand. I normally use 700x28C Presta, with threaded valve stem. In both exploding tube cases, the tube had a fairly long longitudinal split (i.e. along its circumference). However, if the tyre had actually unseated before the tube burst, then this would cause any tube to burst pretty quickly, wouldn't it? If it's any help: today's burst tube had the split along the inside seam that would run exactly along the centre of the rim tape, but it wasn't anywhere near the valve. Also, as I mentioned, the rim tape is in perfect condition, with no folds or other irregularities.
- Another possibility that occurred to me was overheating of the rim, but I really can't see that occurring on my commute, because, as hilly as it is, I don't do enough braking to heat the rim up. I did check it anyway, but neither brake pad was touching the rim (I'm always very careful when adjusting the pads), and the rim was cool to the touch.