Update 7/15: Four minutes and $15 spent at the bike shop and now everything's fine. Except my self-image--it turns out you should check the tire for what caused the flat before putting in a new tube. D'oh! Went for a ride of 8 miles on uneven/hilly, off-road terrain after the repair. Rather wimpy, but about two more miles than I've generally been doing. And I'll be going out again tomorrow! Problem is, laziness has led to bad form, so I'm getting numbness in my hands and arms at this distance. Ugh. I might actually go get some gloves...
Motivated by the exercise discussions, I decided to get more serious about my exercise.
I had gone cycling on Firday, but Sunday I wore myself out with some serious garden work and counted that as my workout. Monday I vowed to take a long bike ride instead of taking a day off as usual... once it cooled off, of course. Being naturally lazy, I pushed it late into the afternoon and finally dragged myself out to the garage about 5:30...
To discover a completely flat rear tire (last filled three days ago--before my last workout).
Of course, all the bike shops (a crosstown drive during rush hour away) closed at six. And besides, I wanted to go cycling tonight So with intrepid spirit, I headed to the nearest big-box sports store and picked up an inner tube along with a few other essentials.
Three hours, two tire changes with inadequate tools, one repair job on the new "puncture proof" inner tube (which had a non-standard valve), and a pair of strained (small) hands later... I still had a flat tire.
Today I'm taking it to the bike shop.