I had another set of pedals ready to install, so this morning I went to do the swap. Oops. Not really turning. I managed to get the drive side pedal off, and noticed some corrosion on the pedal threads. Good old bimetallic electrochemistry at work, aided and abetted by the God of Salt. On the non-drive side, I could barely get the pedal to budge. I shot it with a bit of Liquid Wrench, greased the drive side pedal, reinstalled it, then rode to work.
On the NDS, the shoulder that normally butts up against the crank arm is now moved back just a skosh from the face of the crank arm. Under normal circumstances, much (most? all?) of the force is transmitted between the pedal and the crank through that interface. I hope the Liquid Wrench and easy pedaling will free up the threads a bit so I can remove the pedal this evening without applying heat. Still, you should take advantage of my mistake (I should have been checking all steel/aluminum interfaces periodically, especially on a bike that sees winter's road salt - shame on me), and check your pedals, seatpost, and stem before they become permanent fixtures on your bike.
