Tony and I were having one of those great rides on the Porcupine Rim Trail. Both of us were in the zone, flowing along on the trail as though we were riding down a sidewalk. Drops, step-ups, rock gardens and all of the other challenging features of the trail passed under our wheels like smooth pavement.
I was running 50 psi, front and rear, in my tires, because I had read an article about tire design which stated that the tires I was running would actually hook up better at higher pressure than low. So, I ran them 12 psi higher than normal just to check that theory out, and it was working like a charm.
We hit the flat, sandy stretch of singeltrack, which comes just before the trail drops down into the canyon heading to the Colorado River, and stood up to crank out a few more miles per hour. I was in the big ring, pumping the cranks when I heard the unmistakeable sound of air escaping from a tube.
My front tire got squirrelly, and I almost went down as I stopped. Tony pulled up behind me.
"I must have run over a cactus thorn, or something," I said. "I've got a flat on the front."
I pulled the wheel, and stripped off the tire. After I pulled the tube out, I pumped a bit of air into it, to find the hole. I didn't find a hole, though. I found two...snakebite!
"How the hell did I get a pinch-flat, riding on sand, with 50 psi in my tire?" I asked.
"Wow, that's weird," Tony said, looking back down the trail. "There isn't a rock on the trail for 100 yards."
I patched the tube, and put it in my CamelBack pack, and installed a new one. Then, we took off, again.
I never did figure out how I got that flat.