Jon and I went to Joe Pool Lake today so I could practice on the mountain bike trails. It was easy to find the park, but it took some looking to find the trails. And before I rode 15 minutes, I got a flat tire. I didn't see anything wrong with it, so I pumped it up, and it went flat again in about 5 feet. Gggrrr. At that exact moment Jon walked up (he was hiking the trails while I rode), so we walked out together, and went to the bike shop for some new tubes.

The nuts on the back tire were very stubborn, and needed some coaxing with WD-40 and a mallet. There was a tiny hole in the tube. Cursed thing. We replaced the tube, and I went for a ride, and everything seems to be working now.