1. I have my fav c34 wheels which are 10 speed, I just got hold of a RD-6770 shifter (10 speed).. I assume I can operate that shiter with my Dura ace 11 speed levers? (ST-7970)

    Or will I run into some firmware issues (I tried to read a bit in the other comment fields, but unfortunately got lost)

    Thanks for a great article here

    1. Author

      Nothing from the first generation (4-conductor / 5-conductor) Dura-Ace Di2 7970 system is compatible with any other newer system. It was replaced by the (2-conductor) E-tube systems. No parts are inter-operable between 7970 and any other Di2 System. The wires are completely different.

      1. My mistake here! I’m mixing up two of my projects.. im trying again!

        Will 11speed levers (ST-9070!) fit an 10speed RD 6770 – they do both run on e-tube.. but not sure if it will work..

        In short i have a fully working 11 speed di2 setup, and I want to replace my 11 speed rear dereailuer with the 10 speed RD-6770, due to my wheels…

        Will that work?

        1. Author

          The levers will work with the 10-speed rear derailleur. However, a 10-speed rear derailleur will not work with a 9070 (11-speed compatible) front derailleur. The front and rear derailleurs must both be 11-speed or must both be 10-speed compatible. This limitation is built into the Shimano firmware.

          1. Great thanks for your answer, do you know if they will work automatically or do I need to program something in the e-tupe app/software?

          2. Author

            It should work automatically. If it does not, you will need to update firmware via the Shimano eTube app (Windows + USB adapter or Mobile + Bluetooth component.)

    2. Some (many?) 10 speed wheels can have 11 sprockets put on them and that might be the easiest solution. In some cases using the wheel as the lathe and a dremel to grind the freehub body works. This does not work well with actual Shimano freehub bodies because the spline slots are not well-formed inside of the original mounting face. In some cases new freehub bodies are available and a bit of redishing the wheel works; this is true for some Shimano 10 speed wheels. In some cases machining the inside of the inner rear sprocket cluster works, noting that the same money to buy a 10 speed electronic system could purchase a harbor freight mini-lathe to do such work. And there are probably still a few commercially available 11 speed casssettes that fit 10 speed rear wheels, for example I believe the Shimano 11-34 mountain 11 speed cassette, and I believe Recon still makes one that may be in a hidden menu somewhere. In the case of Mavic no extra work is needed. And in some cases there is not enough room and there is no easy way to make the room.

      1. Thanks for good comments here, I agree there are some solutions which can make it work-ish… dremel through those beautiful DA hubs is not an option. I have had succes of simply remove a sprocet from the 11speed cassette and space my way out of it…

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