##$%&*^$#!!!!!!!!! Got home from a night ride last night [and requisite beer], decided to put on new chainring bolts and a new rear cog on my SS. "Hmmm. I should probably test ride this to make sure the 8-year old chain will work with the brand new cog. Then again, I'm pretty sleepy..."

Got up this morning, grabbed my bike and rode exactly 4' before having the chain skip on the new cog like a hyperactive kid playing hopscotch. Ran to the garage, grabbed my road bike and tried to switch the pedals over. Holy ****, those things were on tight. Finally got the pedals switched, then remembered why I don't commute on my road bike - full race crouch, rock-hard seat. At least I was faster. Not fast enough to make any of the lights on my way in, of course.

The worst part of it is, I know better than to mate up a chain and cog that aren't of a similar vintage. Dumb-de-dumb-dumb-dumb!