To some this may be common knowledge that DynaSys is DynaSys and they are compatible. There has been some confusion about whether or not Shimano DynaSys is the same actuation ratio for all speeds. Some people claim 10, 11 and 12 speed DynaSys are different, possibly due to a shop hand not wanting to take a risk with a customer, a Shimano rep not wanting to state compatibility, other compatibility non-cable-pull issues, or suboptimal performance when not using matched parts. Other people might point to examples where people said it worked or didn’t work or reference YouTube videos.
The strongest evidence that the cable pull is the same and not merely similar is based on Shimano 2020-2021 compatibility charts. RD-M5120-SGS is shown as equivalent to RD-M6000 in 10 speed and RD-M7000 in 11 speed, both of which are officially DynaSys. That pretty much shows that 10 speed and 11 speed DynaSys are the same. RD-M6100 and RD-M5100 are also very similar and the box for RD-M9100-GS lists 11/12s compatibility and the M9100 shifter has an 11s option.
That isn’t to say you won’t run into issues. Jockey wheel and cage designs are different. Cages with the upper pulley concentric to the pivot tend to perform well with front chainrings. Cages with high offset tend to be for 1x. Cages with medium offset are a compromise. This is because the offset moves the upper pulley depending on the amount of chain wrap. With 1x, this only varies with the cassette, so the offset is repeatable and assists shifting for each gear. With 2x or 3x, the front rings also affect the chain, so the cage will be in a different position in different chainrings on the same cog. It isn’t exactly clear why Shimano uses both a high offset and a slant for 1x except for stubbornness.
On one bike I have a DynaSys 11 speed XT shifter and a 10 speed RD-M786 rear (with clutch low/off because Shimano’s design causes additional drag after shifting to a larger cog and I shift more frequently than it needs to settle in, this is obvious if you’ve ever adjusted gears in a stand, and confirmed by CeramicSpeed), with a Chinese 11 speed 11-36 cassette and SRAM 11 speed chain. It shifts fine. Keep in mind that different generations of Shimano are designed for different ranges of cassettes and with Shadow+, cage length is about chain wrap capacity and the derailer can not dynamically adapt to different cassette sizes except with cage offset (which works for 1x, but not so much for 2x or 3x). Some people also report SRAM 1:1/Exact Actuation works with DynaSys. They may be right for 10 speed but I was unable to get a full 11 speeds out of an older 9/10 speed SRAM X9 (listed as both 1:1 and exact actuation). This setup required losing the smallest cog and required a double shift for the largest cog. Otherwise it indexed fine, so it may very well work fine for 10 speeds. Clearly these are suboptimal combinations, but they still worked, and it shows that cable pull charts can be deceptive and people on the internet often give opinions based on a complete lack of evidence in an effort to come across as knowledgeable.
Kuromori 