I'm back into fixing bikes after a many-year hiatus.
One thing I still don't get is indexed front derailleurs. Chain angle changes when you shift in the rear, and you need to tweak the front derailleur. But you can't. Huh?
Also, to get the front derailleur right for one chainring, it's wrong for one or two other chainrings. On my new bike (which I just built with Ultegra 9-speed stuff), the chain rubs the front derailleur on the left side when it's on the smallest (of three) chainring. If I adjust to eliminate that, then it will rub on the outside when it's on the largest chainring. In other words, the distances between the chainrings need tweaking, but I don't believe it's possible.