What's going on here then?
Two separate punctures today in the same tube. Specialized tubes and Ground Control tyres, both only one ride old. First puncture was whilst riding steadily uphill, didn't hit any rocks, just a forest road, tube just started hissing and was flat within 10 seconds. Fixed that one which was a split about 2-3mm long on the inner circumference of the tube, i.e. next to the rim tape.
10 mins later, going down rocky singletrack this time, and the same thing happens. Same size split in a different place, but again on the inner circumference of the tube, plus one opposite on the outside.
Tyres were up at about 55psi, but wouldn't a pinch flat be at the side of the tube anyway, not the inside? Can't find anything within the tyre, wheel or rim tape amiss. The tyres fold so I guess they're Kevlar sidewalks - could this be what's making the difference (never had flats like this before), or just a duff inner tube?