I am upgrading my bike and bought a used Ultegra front derailleur, not considering the size issue. Turns out the derailleur is for 31.8 mm tubing (1 1/4") while mine is 28.6 mm (1 1/8"). I saw an ebay add mentioning shims that can be used to adapt the 31.8 mm derailleur for the smaller frame tubing. Here's the link:
Ebay item number : 380128833518
Is this actually a viable option? It'd save me a heap if it was, but I don't want to Mickey Mouse this either! Thanks in advance for any input!