12-speed Dancing Cassette Wobble/Oscillation
If you ever have a hard time adjusting a 12-speed Di2 rear derailleur, spin the wheel and take a good look at the cassette. Does it appear to dance, wobble, or oscillate?
Don't worry, you're not going crazy. Given the right circumstances, 12-speed Shimano cassettes do indeed have the ability to dance.
That looks something like this:
So what's up with the wobble seen above?
The key is the Adhesive Ring that is stuck to the back of every 12-speed cassette.
Note that in some cases the last two sprockets are not on correctly, and that will cause a wobble at only that end of the cassette. If this is happening to yours, feel free to skip the adhesive ring part of this post and skip to the relevant section.
What does the adhesive ring do?
Twelve-speed adhesive rings are glued onto the back of cassettes, and their main purpose is to eliminate the potential for creaking/squeaking caused by the cassette - freehub body interface.
Does it work? Probably.
Does it also introduce another potential point of bad shifting? Definitely.
What causes the wobble?
When the adhesive ring is on correctly, as shown above, it's all good. However, sometimes these rings get misaligned or even bent and damaged. Here is an example of a misaligned adhesive ring:
And here is an example of a bent or damaged adhesive ring.
Now... I bent my adhesive ring on purpose, to show what that does to a cassette. As you can imagine, this is enough to throw off cassette alignment and shifting.
Why this happens is not clear. It seems to have something to do with the freehub base, and whether or not it has gaps in it as well as the tolerances and how well the adhesive ring is centered.
If your cassette isn't moving around, great! When your shifting goes off all by itself though, you now know what to look for.
Replace or remove the adhesive ring
What can you do if this happens to you? You've got two options:
- Replace the adhesive ring
- Remove the adhesive ring
In their Dealer manuals, Shimano shows how to replace the adhesive ring. Basically, you buy a new one (part number), then remove the old one, clean the surface, and stick a new one on.
Remove the adhesive ring
This is my preferred method. The adhesive ring is supposed to reduce drivetrain noise, and I have never had any problems with that myself. Instead, I have removed the ring on all of my bikes, and it seems people that have had problems with the ring agree.
Removal doesn't hurt, and reduces the risk of a wobbly cassette dramatically. In order to remove the ring, this is what you do:
- Use a knife or your finger nails and pry the ring off
- Throw it in the thrash
Easy, right? Enjoy your ride. Note that you may have to slightly adjust your rear derailleur after removing the ring. Just one or two steps should do.
Also check the last two sprockets/cogs
The smallest two sprockets on 12-speed Shimano cassettes interlock, and it's relatively easy to get those on wrong. Be very careful when installing a cassette and pay close attention to the last (smallest) two sprockets.
If you're wondering whether or not yours are on correctly, spin the rear wheel and take a good look at these sprockets. If they appear to move from left to right, take the cassette lock ring off, and be sure to install the sprockets correctly.
I hope this helps. Did you have problems with the last two sprockets or the adhesive ring? Did removing the ring help? I'd love to hear all about your experiences!