The gashes don’t look like much:
Not even from the side:
When they happened, I knew where to look, because the Kevlar-belted Primo Comet had two conspicuous bulges surrounding debris jammed between the tread and the carcass along the sidewall: the gashes were wide open!
Much to my astonishment, the tire hadn’t gone instantly flat.
Some screwdriver probing in the leftmost gash produced this nasty glass chip:
AFAICT, the smooth side slid over the internal Kevlar belt as the edge sliced between the rubber tread and the carcass. I think the top entered first, with the somewhat crushed end hitting the pavement on each revolution:
The other gash emitted a somewhat smaller chip.
I rode over something crunchy, most likely the remains of a beer bottle, in a shaded section along Rt 376, and we stopped a few driveways later to diagnose a once-per-revolution thump from the front tire. The tube still wasn’t losing pressure, even after extracting the glass, so I continued the mission; it was a fine day for a ride!
I later filled those gashes (plus a few others) with silicone rubber to keep grit out. It’s surely a feel-good gesture, but maybe it’ll help the tire reach the end of its tread life.
You can judge our “riding environment” by the tire’s condition …