Well, the first foray back into mountain biking was less than glorious. Chris Pyzer and I met at the trail-head of the Don for a ride, but I got a flat tire just before arriving.

Of course I didn't have a pump, patch or tube with me. But thanks to the amazing Doug, a random cyclist by who went home and got a tube and returned with it, I got back on the trail. It's people like Doug who restore my faith in human nature.

However, shortly afterwards I got another flat. This is surely a sign from the Great Magnet that I am not to go mountain biking today. After arriving home I discovered the culprit, which is what I had suspected. I used these rims for touring and had put a brass insert into the rim to convert from Schrader to Presta valves. At the lower pressure of the mountain bike tire, the tube sheared along the insert, cutting the valve as it inserts into the tube. So it's back to Schrader valves for me. An inauspicious end to what has been a pretty good day.