Rear tire that is. I was just exiting a turn at the Burnaby Velodrome when FFFSSSSSSTTT! my back tire goes flat. My first instinct was to grab for the brakes. That didn't work for obvious reasons. So I did my best to control the bike but the back wheel just slid out from under me and I went down on my right side then slid down the track head first on my back very ungracefully. I came out unscathed except a small spot of road (track) rash on my knee. The bike needed a new tube of course and handle bar tape.
The cause of the flat is a mystery. It doesn't look like a pinch flat, there were no burs, sharp edges, debris, or anything that might have caused a puncture. Just a big gaping hole in the tube that let all the air out.
Before any one tells me I would go tubeless if there were not so expensive!