This new generation of Ultegra 6870 Di2 has been refined and improved from the previous generation of Di2 components. The main differences are in the rear derailleur and front derailleur, with only minor changes to the shifters. Let's take a closer look at the old and new Ultegra Di2 RD and FD, and see the differences and similarities.
New Ultegra Di2 6870 FD, 138 grams
Old Ultegra Di2 6770 FD, 167 grams. Heavier by almost 30 grams.
Old FD on the left, new FD on the right. The new FD is much smaller in size!
The difference in size of the servo motor, as seen by the size of the casing
New FD is shorter and more compact
Comparing the size from the rear
Another picture comparing the size of the servo motor. This new Ultegra Di2 FD is similar in size to the Dura-Ace Di2 FD.
Some hollow rivets are used for the new FD as shown on the right side
Wire connection port on the new FD is located at a more hidden location
See the difference in the wire routing. Wire for the new FD exits at the rear, which makes it neater than the old FD.
The major difference for the Ultegra Di2 FD would be the size of the FD. This new generation of Ultegra 6870 Di2 FD is much smaller in size than the previous generation. Now, the Ultegra Di2 FD is similar in size to the Dura-Ace FD, which is great.
Another difference is the wire routing, which is neater on the new FD, as it exits at the rear-bottom, and can be well hidden by the frame. Other than these differences, the other parts of the new FD look similar to the old design.
Next, we will compare the old Ultegra Di2 6770 10 speed RD to the new Ultegra Di2 6870 11 speed RD.
New Ultegra Di2 6870 11 speed RD, 256 grams
Old Ultegra Di2 6770 10 speed RD, 272 grams.
Obvious difference in size between the new RD on the left and the old RD on the right
The servo motor on the old RD is much larger than on the new RD!
The old RD sticks out a lot more than the new RD
The limit screws have been moved from the bottom to the top of the RD
The linkages have been changed, with the crash protection arm located at the bottom of the new RD instead of at the top for the old RD
Close up look at the crash protection arm on the new RD
For the old RD, the limit screws are located at the bottom, together with the stopper plate of the RD.
Similar to the FD, the main difference for the RD would be the size. As seen from the pictures above, the new RD is much smaller in size than the old RD. In fact, it is similar in size to the new Dura-Ace Di2 9070 RD. All other parts look quite similar, and the wire connection port is also located at the same area on top.
In summary, for this new generation of Ultegra Di2 6870 RD and FD, the component sizes have been greatly reduced compared to the previous 6770 generation. The sizes are now very similar to the Dura-Ace Di2 9070 components, which is really good. This makes the Ultegra Di2 components a very good deal, as the performance and size is similar to Dura-Ace, and yet is available at half the price of Dura-Ace.