Coldest morning ride so far this season. 19F when I left. Good ride; I dressed properly so I wasn't too hot or too cold. I noticed my rear tire getting soft about 2 miles from work. Got off and checked it and it was down to 20psi. Pumped it up to 40 just to get the last bit in to work and it was almost flat when I got there. I'm currently trying to find the leak. There were a few bits of glass and gravel stuck in the tire, but none seem to have punctured the tube. I'll have to dip it in a toilet and look for bubbles.

I've said it before and I'll say it again: do NOT buy Gatorskin tires. This makes 4 flat tires in under a year on mostly clean suburban roads.