The Shimano FD-6870 [paid link] front derailleur is a precision-engineered component from the Ultegra Di2 electronic shifting series. When installed and adjusted correctly, it provides smooth, reliable, and lightning-fast front shifting. However, even small mistakes during installation or setup can lead to poor performance, noise, or inconsistent shifting. This guide explains the most common reasons why the FD-6870 [paid link] front derailleur might not feel properly set up and provides clear steps to resolve these issues.
Understanding the Shimano FD-6870 Front Derailleur
The FD-6870 [paid link] is an electronic front derailleur designed for Shimano’s Ultegra 11-speed Di2 groupset. Unlike mechanical derailleurs, it relies on electronic actuation for precise movement. Correct alignment, limit setting, and integration with the Di2 system are critical for optimal performance. Riders often assume electronic derailleurs require little adjustment, but accurate mechanical positioning during installation is just as important as with mechanical models.
Tools Required
- 5 mm Allen key
- 2.5 mm Allen key
- Torque wrench [paid link] (recommended)
- Di2 charging cable (for system updates and diagnostics)
- Clean rag and degreaser
Common Setup Mistakes with the FD-6870
Several recurring mistakes lead to poor setup of the FD-6870. These include:
- Incorrect derailleur height relative to the chainrings.
- Misaligned derailleur angle, causing chain rub and noise.
- Poor limit screw adjustments, leading to dropped chains or incomplete shifts.
- Failure to perform the electronic trim adjustment procedure.
- Using incompatible chainrings or cranksets outside Shimano’s recommended range.
- Overlooking firmware updates for the Di2 system.
Each of these issues can prevent the derailleur from operating at its best.
Incorrect Derailleur Height
The FD-6870 must sit 1–3 mm above the tallest tooth of the large chainring. If the derailleur is too high, shifting becomes sluggish. If it is too low, the cage may strike the chainring teeth, producing noise and resistance. Adjusting the height requires loosening the mounting bolt, repositioning the derailleur, and tightening it back at the correct height.
Misaligned Derailleur Angle
The derailleur cage must align parallel to the chainrings. Even a slight angle can cause constant chain rub or difficulty shifting between chainrings. To correct this, loosen the mounting bolt, align the cage carefully, and re-torque to Shimano’s recommended specification. Proper alignment is crucial before moving on to electronic adjustments.
Limit Screw Misadjustments
The FD-6870 uses two limit screws to set the boundaries of derailleur movement. If these screws are too tight, the derailleur cannot shift fully into gear. If too loose, the chain may overshift and drop. To correct this, adjust the low limit screw so the cage just clears the chain in the small ring, then set the high limit screw to allow smooth movement into the large chainring without overshooting.
Skipping Electronic Trim Adjustment
Unlike mechanical derailleurs, the FD-6870 relies on electronic micro-adjustments, known as trimming, to prevent chain rub across the cassette. Skipping this step often results in noisy, inconsistent shifting. Using the Di2 adjustment mode, fine-tune the derailleur position by small increments until the chain runs silently across all gear combinations.
Compatibility Issues
The FD-6870 is optimized for Shimano Ultegra 11-speed drivetrains with specific chainring sizes. Attempting to pair it with non-Shimano cranksets, unusual chainring combinations, or mismatched components can compromise performance. Always verify compatibility before installation to avoid setup problems.
Overlooking Firmware Updates
Because the FD-6870 is an electronic component, outdated firmware can cause shifting delays or inconsistencies. Using the Di2 charger and Shimano E-Tube software, check for updates to ensure your derailleur is running the latest firmware. Regular updates improve performance and compatibility across the drivetrain.
Step-by-Step Correction Procedure
- Check derailleur height and adjust to 1–3 mm above the large chainring teeth.
- Align the cage so it runs parallel to the chainrings.
- Set the low limit screw to prevent chain rub in the small ring.
- Set the high limit screw to prevent overshifting off the large ring.
- Enter Di2 adjustment mode and perform fine-trim corrections.
- Verify shifting performance across all cassette gears.
- Update firmware via Shimano E-Tube if required.
When Setup Still Feels Off
If shifting remains poor after following the above steps, check for worn components such as the chain, chainrings, or bottom bracket bearings. Electronic derailleurs magnify drivetrain wear issues, so ensuring the entire system is in good condition is essential. If problems persist, a professional bike shop with Di2 diagnostic tools can perform more advanced checks.
Conclusion
The Shimano FD-6870 front derailleur is a highly precise component, but it is also sensitive to setup errors. Most performance issues stem from incorrect height, angle, or limit screw adjustment, along with skipped electronic trim calibration. Compatibility and firmware updates also play a vital role. By carefully following the installation and adjustment procedures, you can restore flawless front shifting and prevent future problems with your Ultegra Di2 system.