Per the title, I have a set of Campy Eurus that worked fine with a Dura Ace 12-23 but when I installed an Ultegra 11-28 and then even a 105 11-25 it hops when attempting to engage the 11cog. Doesn't matter large or small front ring. All the other gears work fine. Is there anything special shim wise that I need to look at?
The bike is a 2002 Trek 5200 USPS with recent Ultegra 6700.