So I'm coming to the end of a major (for me) operation where whole bikes' worth of components are getting swapped between frames. Sunday night I finish assembling bike B, bike A is still awaiting a part, so I decide to ride bike B until bike A is finished. "Just a day or two" I think, "I can chance riding light for that short time; no seatbag, no pump, no patch kit, no tools." Note to self, first ride after a frame-up rebuild, the proper attitude is "bring the whole toolkit because you never know what you might have borked up!"
Well on the way to work, I notice my FD is acting funny. It was well-aligned last night on the stand, but now it's rubbing a lot in the small cogs for both the middle and large chainrings. And hey that's weird, now it doesn't even want to drop to the small chainring. I shrug it off, figure I'll readjust when I get home. Although, something doesn't add up: middle/big ring rub on small cogs means FD is not outboard enough; but not dropping to small ring means not inboard enough. (Anybody want to guess the problem before reading on?)
Don't even look at FD all day, even though the bike lives in my cube with me. Riding home, I notice rub is even worse; and it totally doesn't want to drop to small chainring. I help it there manually, ride a while in the small ring, crest the hill, rest of the way home is downhill. I coast down to the stoplight, when it turns green, I pedal through the intersection, approaching a nice descent now, I push up to the middle ring and KAPOW (last chance to guess before I give the answer)
As I was saying, KAPOW I see a tiny flash of light rocket forwards out of the corner of my eye, I think my FD has exploded! I pull over and I see it is just hanging there by its cable; the bolt that used to be holding it onto the clamp is back there in the gutter (fortunately easy to find!); the outermost couple of threads in the FD are never to be seen again.
Obviously (now) in all my loosenings, adjustings, tightenings, testings, I had forgotten the last tightening of that braze-on bolt, and it worked its way loose over a few miles, the FD was hanging crooked (would have been obvious to fix even by hand if I had bothered to look), causing the peculiar shifting behavior, until finally the last few threads were barely holding on, and I went and tried to shift, and KAPOW...
So there I was sitting on the side of the road, with no tools. If I had at least my bike multitool I would have been able to remove the FD from its cable, open the chain with masterlink, take the FD off entirely, and easily make it home with 1x8 (actually 3x8, since it takes only a few seconds to stop, manually move the chain to the desired ring, and proceed).
Strangely I did have the foresight to pack my rarely-turned-on cellphone in my backpack (yes, I had a whole backpack with just a shirt, socks, underwear, lunch, and a cellphone in it -- I could have brought virtually all my tools if I weren't so stupid!), and I had to suck it up and call home for a ride. Or walk about 4mi. With SPD shoes and a bike with 0 flat tires.
So let this be a lesson to you (and to me!!): don't be stupid!