What follows is another mechanical tale of woe in the category of "don't try this at home" (or anywhere else for that matter).
My Serotta's rear derailer shifting was kind of dodgy. When I got the bike it had bar end shifters and the rear one had died. Somehow I found someone in NEBC who gave me an old set of Campy Ergo shifters. Everything else is Campy who in their wisdom makes their equipment incompatible with everything else (everything else being Shimano, the Microsoft of the bike world). So I was a happy camper, I could keep the Campy drive train and still have the benefits of integrated shifting.
It worked but not very well, it would shift up to a larger cog ok, but on many gears when you tried for a smaller cog, it would just hang. Either that or shift down two cogs. After enduring this dodgy behavior for a while, I decided it was time to fix it. For a fleeting instant, I considered taking it to the bike store but I knew this would be big bucks, since the parts are ancient enough that they couldn't easily be replaced and I would probably have to spring for a whole new Shimano setup. I couldn't in good conscience do this, not when I had a small bike's shop worth of inventory already in my garage. I was sure I could somehow make it work.
So one day I spent about an hour adjusting every which way, but couldn't get it so it would upshift and downshift consistently. Then I noticed the chain was riding high on the chainrings by about 1/8"; a pretty good indication of a mighty worn chain. Not too surprising considering I had never changed the chain in all the time I had the bike. So I figured this would be the solution to my shifting problems.
Rooting around in my parts bin, I came across a Regina chain. For some reason I decided this would be a good match for the rest of the Campy parts, maybe because it was also Italian. So I put this on, which meshed much better with the chainrings. But the cog set was another story. If you leave a chain on too long, it wears the cogs, so that when you put a new chain on, they don't mesh well and you get chain skipping. So conventional wisdom is to always replace the cog set as well if the chain you're replacing is very worn. But I have experimentally determined that if you just tough it out with the new chain and old cog set, after a while the new chain will wear itself into the old cog set. You just have to endure chain skipping for several hundred miles. Skipping is usually worst in the small cogs, since they have fewer teeth to grab onto the chain, or the middle cog which is used the most, hence most worn. When skipping happens, you just need to downshift until you find a cog that doesn't skip.
When I first put the chain on, it was making awful noises, and I realized that I had wrapped the chain the wrong way around the pullies. So I had to break the chain and start over. Amazingly enough, I managed to get the chain on wrong the second time. At this point, I really didn't want to break the chain again, so I fixed the problem by detaching one of the pullies and rerouting the chain.
I took it out for a test ride/chain break-in. I made sure not to stray too far from home lest something go wrong (which turned out to be an excellent decision). I experienced the expected skipping but it seemed worse than normal. It started making awful noises until finally the chain locked up. Seems I hadn't tightened the pulley sufficiently and it worked loose and was now missing in action. For a while I thought I was in for a several mile walk in cleats. But I managed to find one gear where I could get the crank to turn in, and aside from having to walk up a couple of steeper sections, made it home without incident.
Another reason I was having problems was that the Regina chain, despite sharing a common mother country with the rest of the drive train, was actually a tad too wide for the eight speed spacing. It fit, but just barely, and most of the unhappy noises I was hearing was the chain bumping into the cogs. So back to the parts bin, where I found an old Sedisport chain. It was actually new chain, but had been lying fallow for quite a while, as evidenced by the date 2/22/1990 on the box. This time I actually took a pair of calipers and determined that this chain was comfortably narrower than the cog spacing.
The test ride with new chain was much more successful, I was able to push moderately hard in most gears without skipping, but the shifting remained as dodgy as it was before I started. Probably should have just taken it to the bike store in the first place.
Please send corrections, additions, comments and praise to