Hit the halfway point this morning - 10 miles in, 10 to go, and Pssssshhhh! A rear flat. Happily it was at a point with streetlights, so I pulled the gear off the bike, flipped it over, and pulled the tire. No sign of whatever caused the flat - the tire was intact, nothing stuck in the tire - nada. Pumped the tube up a bit to find the leak, patched the tube, put it all back together, checked for pinch flats, aired it up and Psssssshhh! Flatted again. Composed a sonnet. (Well, uttered words anyway.) Took the tire apart again, looked for anything that might be causing a flat again...nothing. Out of paranoia (and to save patching time) I got the brand new spare tube out and put it in instead. Put everything together being doubly sure the tube wasn't pinched and...it held air. *Whew* Put the tire back on the bike, trying to seat it well. Flipped the bike over, and the wheel was just off enough that the rear brakes rubbed. *Sigh* Flip the bike, re-reseat the wheel, all better.
8 miles later the rear tire went flat. Again. Recited Shakespeare. Then I pushed the bike the last two miles to work.
I have since pulled the wheel again. I looked at the spokes. I looked at the rim tape (it's a new rear wheel.) I went over every inch of the tire, both inside and out. I cleaned everything. When I pumped up the new tube, it has an odd constriction right where the hole was. (All of the holes were in different spots, by the way.) I patched it up, patched the original tube, put everything back together carefully, etc and the tire is holding air. For the moment. Here's hoping the ride home is uneventful.
Man am I glad I have a road morph pump. At least pumping up tires repeatedly is easy...