Good advice from all, thank you - and the more I think about it, I think I agree that it's a flexibility issue/biting off more than I was ready to chew issue. My rides this year have been either MTB'ing (where I seem to be able to coast as much as pedal) and road biking w/hills under 6 miles. This rail trail is 100% pedaling - it's so flat that there's rarely an opportunity to coast. I have had a bike fit (when I purchased the bike about 3 years ago) - I think I really did just overlook the fact that it's been a crappy summer and I haven't been out nearly enough to tackle that ride (the heart was willing, just not the one knee!). That being said, I'll rest that knee up, take the bike in for another check for fit and have the shoes looked at and try not to let my pride get in the way of common sense next time!