Ok, let’s simplify this a little. Until Shimano launched the new Dura-Ace R9120 and R9170 groupsets, the Japanese giants had actually refrained from uniting a disc brake system with a specific groupset. Until that launch, the BR-RS805 calipers were the highest-spec system it made, and tended to come packaged with either Dura-Ace or Ultegra drivetrains.
With the launch of the R9120 and R9170 Dura-Ace systems, the industry has naturally shifted the BR-RS805 system to Ultegra’s level, instead of a Dura-Ace/Ultegra crossover.
That’s fine by us, because as we’ve seen in various bike tests over the past year or so, it’s an excellent system and has generally kept Shimano current with higher-end disc brake bikes. As an aside, we also like the hint with the new Dura-Ace that Shimano are looking to tidy up their disc brake offering by giving spec-level names to their rotor stoppers too.