How to Install, Adjust, and Maintain the RD-6870 Rear Derailleur

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in Rear Derailleur, Shimano, Ultegra

The Shimano RD-6870[paid link] Ultegra Di2 rear derailleur is a crucial component of electronic shifting systems, offering precise, consistent gear changes with minimal effort. Proper installation, adjustment, and maintenance ensure optimal performance and longevity.

This guide covers step-by-step installation, fine-tuning, and maintenance procedures to keep your RD-6870 functioning flawlessly.

Tools Required [paid links]

Understanding the RD-6870 Rear Derailleur

The RD-6870 Ultegra Di2 rear derailleur is an 11-speed electronic derailleur compatible with Shimano’s E-Tube Di2 system. It features:

  • Servo-assisted electronic shifting: Ensures consistent gear changes without cable stretch issues.
  • Low-profile Shadow design: Enhances aerodynamics and reduces crash vulnerability.
  • Automatic crash recovery: The derailleur repositions itself after impact.
  • Compact motor and efficient linkage: Provides rapid and accurate shifting.

Before installation, ensure compatibility with your frame, cassette, and chain.

Step-by-Step Installation of the RD-6870 Rear Derailleur

1. Mounting the Derailleur

  1. Ensure the derailleur hanger is straight using a derailleur alignment gauge.
  2. Apply a small amount of grease to the derailleur mounting bolt threads.
  3. Thread the derailleur onto the hanger using a 5mm Allen key.
  4. Torque to 8-10Nm using a torque wrench[paid link].

2. Connecting the Di2 Wires

  1. Identify the correct E-Tube port for the rear derailleur.
  2. Insert the Di2 cable into the port until it clicks into place. Use a Di2 e-Tube wiring tool for proper insertion.
  3. Route the cable neatly along the chainstay to avoid interference.

3. Installing the Chain

  1. Select an 11-speed compatible chain.
  2. Wrap the chain around the largest cassette cog and chainring, bypassing the derailleur.
  3. Add two extra links before cutting the chain.
  4. Use a quick link or Shimano-specific chain pin for secure connection.

4. Aligning the Derailleur and Setting B-Screw

  1. Shift to the smallest rear cog and check the jockey wheel position.
  2. Adjust the B-screw to set proper clearance between the top jockey wheel and the cassette (approx. 5-6mm).
  3. Use a digital caliper[paid link] for precision if needed.

Adjusting the RD-6870 Rear Derailleur for Optimal Shifting

1. Setting the High and Low Limit Screws

  • High Limit (H-screw): Ensures the chain doesn’t shift past the smallest cog.
  • Low Limit (L-screw): Prevents the chain from overshooting the largest cog.
  1. Shift to the smallest cog and adjust the H-screw until the jockey wheel aligns directly beneath the cog.
  2. Shift to the largest cog and adjust the L-screw similarly.

2. Fine-Tuning the Indexing via Di2 Adjustment Mode

  1. Enter adjustment mode by holding the Di2 shifter button until the LED indicator blinks.
  2. Use the shifters to micro-adjust the derailleur until the chain runs smoothly in each gear.
  3. Exit adjustment mode by pressing the button again.

Maintaining the RD-6870 Rear Derailleur

1. Regular Cleaning and Lubrication

  1. Use a degreaser and brush to clean the jockey wheels.
  2. Wipe down the derailleur body with a microfiber cloth.
  3. Apply a small amount of dry lubricant to the jockey wheels and pivot points.

2. Checking for Wear and Damage

  1. Inspect jockey wheels for excessive wear and replace if necessary.
  2. Check for bent derailleur hangers using an alignment gauge.
  3. Ensure all Di2 connections are secure and free from corrosion.

3. Firmware Updates and Diagnostics

  1. Connect the Di2 system to Shimano E-Tube software.
  2. Check for available firmware updates and install them.
  3. Run a diagnostic test to identify potential electronic issues.

Common Installation Mistakes and Troubleshooting

1. Misaligned Derailleur Hanger

  • Symptoms: Poor shifting performance or skipping gears.
  • Solution: Use a derailleur alignment gauge to check and realign the hanger.

2. Loose or Improperly Connected Di2 Wires

  • Symptoms: Non-responsive shifting or intermittent function.
  • Solution: Reinsert the wires securely and ensure proper routing.

3. Incorrect Chain Length

  • Symptoms: Chain slack or excessive tension in some gears.
  • Solution: Verify the chain length using the large-large method.

RD-6870 Rear Derailleur Compatibility and Upgrade Options

The RD-6870 Ultegra Di2 is compatible with:

  • Shimano Ultegra 6870 Di2 shifters
  • 11-speed Shimano cassettes (11-28T, 11-30T, etc.)
  • Shimano Di2 battery systems (SM-BTR1, BT-DN110, etc.)

For those seeking an upgrade, the RD-R8050[paid link] Ultegra Di2 offers faster shifts and enhanced motor efficiency.

Conclusion

Proper installation, adjustment, and maintenance of the Shimano RD-6870 rear derailleur ensure smooth, reliable electronic shifting. By following these steps and maintaining the system regularly, riders can maximize performance and extend the lifespan of their derailleur.