For Dura-Ace components, being lightweight is very important. Having the best function is also required. In this case, the shifter was totally redesigned to create the new ST-R9170, as compared to the ST-R785.
New Dura-Ace ST-R9170 weighs only 160 grams per side, giving a total weight of just 320 grams per pair.
Non series ST-R785 weighs 254 grams per side, giving a total of 508 grams per pair, which is significantly heavier.
Rubber hood has a different texture, with the "waffle" pattern used on the new ST-R9170 (right side).
Comparing the side profile, the ST-R9170 is obviously lower in height, which makes it look much more similar in shape and size to the other Dura-Ace road shifters.
Dura-Ace ST-R9170 is lower in height, while the lever shape is also curved outwards to match the other mechanical road shifters.
ST-R9170 on the left looks very similar to other road shifters, while ST-R785 has a large silver cover which gives it a very distinctive look.
ST-R9170 on the left has slightly larger Di2 buttons and a stronger click feeling, for an improved tactile feel.
Rear of the lever is where the mechanism for the buttons are housed. ST-R9170 on the right has a cleaner look as the parts are all black in colour and more concealed.
ST-R785 on the left has a lever stopper on the Bracket, while the wire can also be seen. ST-R9170 improves on these with a reach adjustment bolt at the bottom and hides the wire, while the rubber hood texture has also been changed.
Rear view shows that the new ST-R9170 (right side) has a wider Bracket, and uses a titanium Clamp Band for lighter weight.
Internal profile of the ST-R9170 rubber hood. Due to the multiple protrusions as shown, and the many ribs on the Bracket, it was very difficult to remove and install the rubber hood.
ST-R9170 on the left has many ribs on the resin Bracket for weight savings, while ST-R785 on the right uses an aluminium Bracket.
The Di2 unit is smaller in size on the ST-R9170 (left side), while it is also located more rearwards for easier access. Also note the different wire routing through the Bracket.
The bleeding port for ST-R9170 (left side) is located in the middle of the Bracket (black bolt), while the ST-R785 bleeding port is right at the front of the Bracket. The little bump at the front of the ST-R9170 bracket is the top button which can be programmed.
This side by side picture shows how different the Bracket design is, as well as the different hydraulic design.