The Shimano FD-6770 [paid link] front derailleur was part of the first-generation Ultegra Di2 groupset, introducing electronic shifting to a wider audience. While it marked a significant leap forward in shifting technology, it has since been succeeded by the FD-6870 [paid link], which brought noticeable refinements in performance and reliability. For riders considering upgrades, replacements, or compatibility questions, understanding the technical differences between the FD-6770 [paid link] and FD-6870 [paid link] is crucial.
Design and Construction
The FD-6770 [paid link] featured a pioneering electronic actuation system that eliminated traditional cable pull. Its construction was robust but carried some of the bulk associated with early electronic designs. The FD-6870 [paid link], on the other hand, benefited from a refined design that reduced weight and bulk while improving the integration with the frame and drivetrain. Shimano updated the linkage and arm geometry in the FD-6870 to deliver faster, more precise movement, especially under load.
Shifting Performance
The FD-6770 delivered smooth, accurate shifts compared to mechanical alternatives of its time, but it showed limitations under high pedaling torque. Riders often experienced minor hesitation or chain rub when cross-chaining, particularly on compact chainrings.
The FD-6870 improved significantly in this area. With redesigned motor control and linkage, it provided quicker shifts and reduced the chance of chain drop. Shimano also integrated automatic trim functionality more effectively, allowing the derailleur to adjust its position in small increments and eliminate chain rub across the cassette.
Compatibility with Drivetrain Components
Compatibility is one of the most critical differences. The FD-6770 was designed specifically for Shimano’s first-generation 10-speed Di2 system. It is not natively compatible with 11-speed drivetrains. Riders attempting to use it with newer systems will encounter indexing and chainline issues, making it unsuitable for mixed setups.
By contrast, the FD-6870 was built for Shimano’s 11-speed Ultegra Di2 system, ensuring smooth operation with modern cassettes and chainrings. It also shares greater cross-compatibility with other Di2 components from Shimano’s Dura-Ace and later Ultegra series, giving riders more flexibility for upgrades.
Installation and Adjustment
The FD-6770 required precise alignment during installation, as its adjustment range was narrower compared to later models. Misalignment often resulted in overshifting or chain rub, and the set-up process demanded careful attention to limit screw settings.
The FD-6870 simplified installation with better adjustment tolerances and improved limit screw design. Its wider compatibility with modern braze-on mounts also made it more user-friendly, reducing the likelihood of installation errors.
Maintenance and Reliability
The FD-6770, being Shimano’s first attempt at a mid-tier electronic derailleur, had some long-term reliability issues. Riders often reported inconsistent motor function after extensive use, especially in wet conditions. Additionally, replacement parts for the FD-6770 are increasingly difficult to source, which complicates long-term maintenance.
The FD-6870 addressed these concerns with better sealing, more durable motor components, and improved firmware integration. This made it not only more reliable but also easier to keep in top working condition with regular cleaning and firmware updates through Shimano’s E-Tube system.
Performance Customization
The FD-6770 offered basic functionality but limited options for customization. Firmware updates were minimal, and shifting speed adjustments were unavailable.
The FD-6870, however, integrated with Shimano’s E-Tube platform, allowing riders to fine-tune shift behavior. Cyclists could customize multi-shift settings, shifting speed, and even update firmware to improve long-term functionality. This feature provided greater adaptability for racing, training, and endurance riding.
Which One Should You Choose?
Cyclists still running a 10-speed Di2 system will find the FD-6770 functional but increasingly limited. It remains serviceable for riders who maintain their older Ultegra Di2 groupset, but it lacks future-proofing.
For anyone considering upgrades or replacements, the FD-6870 is the superior choice. It offers enhanced performance, broader compatibility, and easier maintenance. Riders looking to transition to modern 11-speed or even 12-speed systems will benefit from the FD-6870’s adaptability and long-term support.
Conclusion
The Shimano FD-6770 front derailleur was groundbreaking when introduced, but it shows its age compared to the FD-6870. While the FD-6770 remains serviceable within its original 10-speed Di2 system, the FD-6870 is a clear evolution, delivering faster shifting, broader compatibility, and better long-term reliability. For cyclists evaluating upgrades, the FD-6870 provides a tangible improvement that ensures smoother, more precise front shifting for years to come.