Installing a Campagnolo Chorus 12-speed rear derailleur on your road bike is a precise process that requires a solid understanding of both your bike’s drivetrain and the derailleur itself. This guide will walk you through each step, ensuring that your new derailleur is installed correctly, adjusted for optimal performance, and ready for smooth shifting.
Tools Required
- 5mm Allen wrench
- 3mm Allen wrench
- Torx T25 driver
- Chain tool (if removing the chain)
- 8mm open-end wrench (for adjusting derailleur hanger)
- Torque wrench
- Bicycle grease
- Rags for cleaning
Step 1: Prepare Your Bike
Before you begin, ensure that your bike is securely positioned in a bike stand. This will provide you with the stability needed to perform the installation accurately. Check that the drivetrain components are clean, as dirt and grime can impede the installation process.
Step 2: Remove the Old Derailleur (If Applicable)
If you’re replacing an existing derailleur, you’ll need to remove it first. Use a 5mm Allen wrench to unscrew the derailleur mounting bolt, and carefully slide the derailleur off the hanger. If you’re also replacing the chain, use a chain tool to remove it before moving on to the next step.
Step 3: Install the New Chorus 12-Speed Rear Derailleur
- Position the Chorus 12-speed rear derailleur on the derailleur hanger. Ensure that the derailleur’s mounting hole aligns correctly with the hanger.
- Insert the derailleur mounting bolt and tighten it with a 5mm Allen wrench. Be sure to apply light grease to the bolt threads to prevent seizing over time.
- Use a torque wrench to tighten the bolt to the manufacturer’s specified torque (usually 8-10 Nm). This ensures the derailleur is securely attached without being overtightened.
Step 4: Attach the Derailleur to the Chain
- Thread the chain through the jockey wheels of the rear derailleur. Ensure the chain runs smoothly through the derailleur and that it is properly positioned on the cassette.
- If you are installing a new chain, make sure that it is correctly sized for your bike. Use a chain tool to shorten the chain, if necessary, by removing any extra links.
Step 5: Adjust the Derailleur Hanger
The derailleur hanger must be perfectly aligned to ensure smooth shifting. Use an 8mm open-end wrench to adjust the derailleur hanger if needed. If the hanger is bent, use a derailleur hanger alignment tool to straighten it. A misaligned hanger can result in poor shifting performance, so take the time to ensure it is true.
Step 6: Install the Shifter Cable
- Insert the shifter cable into the derailleur’s cable entry point. Depending on your setup, you may need to use a 3mm Allen wrench to loosen the cable pinch bolt slightly.
- Run the cable along the chainstay, threading it into the rear derailleur. Tighten the pinch bolt to secure the cable in place. Make sure the cable is taut but not overly tight to avoid shifting issues.
Step 7: Set the Limit Screws
The limit screws on your Campagnolo Chorus 12-speed rear derailleur control the range of motion for the derailleur. Adjust the two limit screws as follows:
- High limit screw: Adjust the screw that controls the derailleur’s movement toward the smallest cog. Ensure the derailleur does not shift past the smallest cog.
- Low limit screw: Adjust the screw that controls the derailleur’s movement toward the largest cog. Ensure the derailleur does not shift past the largest cog.
Use a 3mm Allen wrench to make small adjustments to both screws. It’s essential to ensure that the derailleur can move smoothly between all cogs without overshooting.
Step 8: Adjust the B-Screw
The B-screw controls the gap between the derailleur’s jockey wheels and the cassette. To ensure smooth shifting, adjust the B-screw by turning it clockwise or counterclockwise. The ideal gap between the jockey wheels and the largest cog is typically around 5-6mm. Adjust the screw until the gap is consistent throughout the entire gear range.
Step 9: Fine-Tune Shifting
With the derailleur installed and the basic adjustments made, shift through all the gears to ensure smooth operation. Pay close attention to:
- Shifting precision: Ensure the chain shifts smoothly across all cogs without skipping or hesitation.
- Chain tension: Check that the chain tension is correct; it should neither be too loose nor too tight.
- Jockey wheel alignment: Ensure the jockey wheels are tracking the cassette correctly without any binding.
Make any necessary fine-tuning adjustments to the barrel adjuster on the derailleur or shifter, and recheck the shifting after each adjustment.
Step 10: Test Ride and Final Adjustments
Once everything is installed and adjusted, take your bike for a short test ride. Shift through the gears under various loads to verify smooth operation. If the shifting is not crisp or if there’s any hesitation, make additional adjustments to the cable tension or limit screws.
After the test ride, double-check all bolts to ensure they are tightened to the correct torque specifications. The final step is to clean up the area and lubricate any moving parts that require it, such as the jockey wheels and pivot points.
Conclusion
Installing your Campagnolo Chorus 12-speed rear derailleur is a rewarding task that enhances your bike’s performance. By following these steps carefully and paying attention to details such as derailleur alignment, cable tension, and limit screw adjustments, you can achieve smooth, precise shifting. Regular maintenance and attention to detail will ensure your derailleur continues to perform optimally, helping you ride with confidence.