The Shimano ST-6870 Di2 shifters are an integral part of Shimano’s electronic road bike drivetrain, offering precision and seamless shifting that riders have come to expect from Di2 systems. Whether you are a professional cyclist or a weekend warrior, proper installation, adjustment, and maintenance are crucial to ensure your shifting system operates flawlessly.
This comprehensive guide will take you through the process of installing, adjusting, and maintaining your Shimano ST-6870 Di2 shifters.
Tools Required
Before beginning the installation and maintenance process, make sure you have the following tools:
- 2.5mm, 3mm, 4mm, and 5mm Allen wrenches [paid link]
- Di2 cable tool (Shimano recommended)
- Di2-specific wire crimps
- Torque wrench [paid link] (for precise tightening)
- Wire management clips
- Phillips head screwdriver
- Di2 cable junction box (SM-JC41 [paid link] or equivalent)
- A computer or tablet with Shimano E-Tube software for Di2 adjustments
- A clean, flat surface for your bike
- Chain checker tool (optional but helpful for maintenance)
Installation of Shimano ST-6870 Di2 Shifters
Installing your Shimano ST-6870 Di2 shifters correctly is essential to achieve smooth shifting performance and system longevity. The process involves both mechanical and electrical steps, but the entire installation can be completed with careful attention.
Step 1: Install the Handlebars and Brake Levers
Start by mounting the handlebars and ensuring they are properly positioned on the stem. Next, install the brake levers onto the handlebars. You can install the Shimano ST-6870 Di2 shifters directly onto the brake lever mounts. Make sure the shift levers are securely attached and the brake lever is positioned in a comfortable, ergonomic position for your riding style.
Step 2: Route the Di2 Cables
The Di2 system requires a precise and clean routing of cables. The ST-6870 shifters come with internal wiring, so the cables should be routed through the handlebars. The most common setup uses the SM-JC41 [paid link] junction box for connecting cables between the shifters, front and rear derailleurs, and the battery.
- Front and Rear Derailleur Cables: Route the cables from the shifters to the respective derailleurs, ensuring they do not rub against any moving parts.
- Junction Box and Battery Placement: The junction box can be positioned on the bike frame or near the bottom bracket, depending on your bike frame’s design. Connect the battery, junction box, and derailleurs using the provided wiring.
Step 3: Electrical Connections
Shimano Di2 systems rely on a series of electrical connections that control shifting. The connections need to be clean and secure to avoid any malfunction. Insert the cable ends into their respective slots on the shifters and derailleurs, making sure the Di2 connectors are pushed in fully until they click into place.
Step 4: Final Tightening and Torque Specifications
Once all the components are connected and positioned, tighten all bolts to Shimano’s recommended torque values. Over-tightening or under-tightening the bolts can lead to shifting issues or damage to the components.
Adjusting Shimano ST-6870 Di2 Shifters
Proper adjustment ensures smooth and responsive shifting. Although Di2 systems are known for their automatic trimming and fine-tuning, some manual adjustments are still required to fine-tune the system to your preferences.
Step 1: Basic Shifting Test
Turn on your Di2 system and begin by checking the functionality of the shifters. Ensure that the front and rear derailleurs shift smoothly across all gears. If you notice any hesitation or inaccurate shifting, you may need to adjust the cable tension or the limit screws.
Step 2: Set Derailleur Limit Screws
The limit screws control the movement of the derailleur, preventing the chain from dropping off the cog or chainring. To set the limit screws:
- Rear Derailleur: Set the high and low limit screws to prevent the derailleur from shifting past the smallest and largest cogs.
- Front Derailleur: Adjust the high and low limit screws to ensure the derailleur does not overshift or rub the chain.
Step 3: Fine-Tuning Di2 with E-Tube Software
Shimano’s E-Tube software provides a more advanced method for tuning Di2 systems. The software allows you to adjust settings such as:
- Shifting Speed: Fine-tune the speed at which the derailleur moves across the gears.
- Trim Adjustments: Even though the Di2 system automatically trims the front derailleur, you may want to tweak this for better performance in certain gear combinations.
- Cables and Connections: Ensure that the cables are functioning correctly and detect any issues with the wiring.
Connect your bike to the E-Tube software via USB or Bluetooth (if using a tablet or smartphone) and follow the instructions to make adjustments. This software helps keep your Di2 system up-to-date with firmware updates and ensures smooth operation.
Step 4: Test Ride
After making the adjustments, take your bike for a test ride to check the performance. Pay attention to the smoothness of the shifting, ensuring there are no delays, skips, or missed shifts. If necessary, return to the adjustment process to fine-tune the settings.
Maintaining Shimano ST-6870 Di2 Shifters
Regular maintenance is key to extending the lifespan of your Shimano ST-6870 Di2 shifters and maintaining optimal performance. Although the Di2 system is designed to be low-maintenance, periodic checks and proper care can prevent issues from arising.
Step 1: Clean and Inspect Regularly
Regularly clean the shifters, cables, and derailleur to prevent dirt and grime from accumulating. Use a soft cloth to wipe down the shifters and cables. Avoid using excessive water around the electrical components, as this can cause damage.
Step 2: Battery Check
The Di2 system operates on a rechargeable battery. Make sure to regularly check the battery level [paid link], as low voltage can lead to poor shifting performance. Shimano recommends charging the Di2 battery every 300-400 miles or when the system indicates low power.
Step 3: Lubricate Moving Parts
Although the Di2 system uses electronic shifting, the mechanical components such as the derailleurs still require lubrication. Ensure that the derailleurs, pivot points, and chain are well-lubricated to avoid wear and tear. Use a high-quality chain lubricant that is suited for road conditions.
Step 4: Check for Firmware Updates
Shimano releases firmware updates periodically to improve Di2 system performance. Regularly check for firmware updates using Shimano’s E-Tube software. These updates can resolve issues, enhance shifting performance, and provide new features.
Troubleshooting Shimano ST-6870 Di2 Shifters
If you encounter shifting problems with your Shimano ST-6870 Di2 shifters, there are several common issues you can troubleshoot:
1. Shifting Hesitation or Sluggishness
If the shifting feels sluggish, the first step is to check the battery charge. A low battery can affect shifting performance. Additionally, ensure that the cables are properly connected, and there is no dirt or corrosion affecting the wiring.
2. Chain Drops or Missed Shifts
If the chain is dropping off the cogs or chainring, it could indicate incorrect limit screw adjustments on the front or rear derailleur. Check the limit screws and ensure that the derailleur is positioned correctly.
3. No Shifting Response
If the shifters do not respond at all, check the electrical connections and make sure that the Di2 system is powered on. A loose wire or damaged cable could be the culprit. Use the E-Tube software to check for any system errors.
Conclusion
The Shimano ST-6870 Di2 shifters offer exceptional performance and reliability, but like any high-end component, they require careful installation, regular maintenance, and occasional fine-tuning to ensure smooth operation. By following the steps outlined in this guide, you can keep your ST-6870 shifters in top condition and experience flawless gear changes on every ride.