I have an Ultegra 6800 11-28 cassette too. What puzzled me though is something I ran into recently. I have DA cassettes on my 2 Parlee's (one is otherwise DA, the other Ultegra). I bought a direct-drive trainer, the Tacx Neo, that comes without a cassette. I put the unused Ultegra on the trainer and could not get it to be silent. I got plenty of chain noise in the middle cogs. I re-mounted, re-torqued, micro-adjusted the Di2 derailleur, futzed for over an hour, maybe 2, getting frustrated, but could not get the noise to go again. I pulled a DA cassette off a spare wheel, and it was silent. The DA and Ultegra cassettes should be totally interchangable, totally the same spacing, but I couldn't get the Ultegra one to be silent. Perhaps someone more skilled than I at rear derailleur adjustment could get it to work quietly. I could not.
I am going to put the Ultegra on the spare wheel and see if it's quiet on the road.
Missed this earlier.
This is a known issue with Ultegra cassettes, especially 11-28. Basically Ultegra cassettes do not run quietly with Shimano chains. I had exactly the same issues as you when I moved away from Dura-Ace cassettes.
The solution is to use a KMC X11-SL chain. Runs completely quiet again.
Ahh, thank you for the reply. Yes, I'm running an 11-28 cassette -- the quiet Dura-Ace one and the two noisy (new) Ultegra ones. I'll have to give the KMC chain a try.
I am going to try the Ultegra cassette on a wheel (C24) and see if it's noisy there. One would think so, and not just on the Edco freehub on the Neo, but worth a try.
I put the bike on a Kickr trainer yesterday at my local bike shop, which has an indoory Kickr cycling studio, and it was quiet. I should find out what cassette they are using.
Unlikely it's a DA -- you wouldn't put ordinarily put a DA cassette on a trainer, but rather a much less expensive one.
Probably a 105, they are quiet as well. It's just the Ultegra that's really noisy. Typically the KMC chain is better than a Shimano no matter what cassette as I'm pretty sure it's marginally thinner than the Shimano chains.