OK, this is a follow up from my post yesterday about going from 12x25 to a 11x25 10sp cassette.
So I took the brand new bike back to the shop, who agreed to swap out my cassette to an 11x25. I just took the rear wheel, and they put it on for me, no problem. I get it home, and put it up on the trainer to check it out. All the gears run smooth...except for the damn 11T. The chain is jumping like crazy, sitting up on the very tops of the cog teeth. It's not trying to jump to the 12, it's just trying to stay on the tops of the teeth. I played with the barrel adjuster, and the limit screw, and I can tell it's not that.
The only thing I can think of is that the dude at the shop put back the 12T lockring. Which brings me to my question. Is the lockring the same on an 11x25 and 12x25 Ultegra 6700 cassette, or are they different? The lockring appears to be a hair larger in diameter than the bottom of the groove in the 11T cog teeth.
What else could be the problem? Chain, bike, and cassette are all brand spanking new. ANNOYING!