We were coming home today from our usual ride. We were all feeling good and had just chased a tandem for about 6 miles of downhill. We were pacelining the usual stop sign - to - stop sign flat, and as I moved up to take my turn at the front, I got what I thought was a noisey flat. Turned out I had a screw in my tire. It had entered the "tread" sideways, but didn't get to the tube. I backed it out and finished the last 5 miles without incident.