Saturday, January 27, 2018

Shimano Road Hydraulic Disc Brake Di2 Shifters: ST-R9170 vs ST-R785

After comparing the mechanical shifting versions, I will now compare the Di2 versions of the road hydraulic shifters. The non series, first generation, Di2 shifter with hydraulic braking is the ST-R785, while the latest second generation is the Dura-Ace ST-R9170.

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.

Another major difference is the pivot location of the brake lever. ST-R785 on the left has a high pivot, while ST-R9170 has a pivot location that is lower and similar to other mechanical or Di2 road shifters. This allows the brake lever ergonomics to be similar to other Dura-Ace shifters.

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.

This new generation ST-R9170 is a significant improvement over the first generation ST-R785, with the major improvements being lower weight, smaller size, and a more conventional braking ergonomics. There is also an additional button on top for extra customization.

2 comments:

  1. Hi, thanks for the detailed comparison. Can you say if there's any difference in reach from where they clamp the bars to the hoods between the two shifters? It's a little hard to make out from the otherwise great photos.

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    1. The R785 is slightly longer in reach by about 5mm or so, so I would run a slightly short stem compared to other road shifters.

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