Review: Performance and Durability of GRX RD-RX820 (12-speed 2x) Rear Derailleurs

Posted on
in Uncategorized

The Shimano GRX RD-RX820 [paid link] is a crucial component in the Shimano GRX series, designed specifically for gravel and adventure riders. As part of Shimano’s 12-speed 2x drivetrain system, it offers superior shifting performance, smooth gear transitions, and enhanced durability for off-road and gravel cycling. This guide will provide an in-depth review of the GRX RD-RX820 rear derailleur, covering its installation, adjustment, maintenance, troubleshooting, customization, and performance optimization.

Installation of the GRX RD-RX820 (12-speed 2x) Rear Derailleur

Installing the GRX RD-RX820 requires a few essential steps to ensure optimal performance. This derailleur is designed for 12-speed drivetrains with a 2x front setup, making it compatible with a wide range of gravel bikes and adventure setups.

Tools Required:

  • 5mm Allen wrench
  • 4mm Allen wrench
  • Shimano chain tool
  • Torx T25 wrench
  • Shimano B-screw tool (if needed)
  • A clean rag or bike maintenance stand

Step-by-step Installation:

  1. Remove the old derailleur (if applicable):
    • Use a 5mm Allen wrench to detach the derailleur hanger from the frame.
    • Remove the existing derailleur and ensure the rear derailleur hanger is free from damage or misalignment.
  2. Install the new derailleur:
    • Attach the GRX RD-RX820 to the derailleur hanger using the appropriate fasteners and a 5mm Allen wrench.
    • Ensure the derailleur is securely mounted and parallel to the wheel.
  3. Install the chain:
    • Thread the chain through the jockey wheels of the derailleur, ensuring it runs smoothly without any twists.
    • Use a Shimano chain tool to properly size and connect the chain.
  4. Adjust the B-tension:
    • Use the Shimano B-screw tool to adjust the B-tension screw. This controls the distance between the derailleur’s jockey wheels and the cassette. For the GRX RD-RX820, this screw ensures smooth shifting and prevents the chain from dragging on the cassette.
  5. Final checks:
    • Double-check that all fasteners are tightened properly.
    • Ensure the derailleur is aligned with the cassette and moves freely through the entire gear range.

Adjusting the GRX RD-RX820 (12-speed 2x) Rear Derailleur

Proper adjustment of the GRX RD-RX820 is crucial for achieving smooth and reliable shifting. The derailleur features Shimano’s Shadow RD technology, ensuring a quiet and stable ride, even on rough terrain.

Step-by-step Adjustment:

  1. Set the high and low limit screws:
    • Using a 4mm Allen wrench, adjust the high and low limit screws to ensure the derailleur doesn’t shift beyond the smallest or largest cogs. This prevents the chain from dropping off the cassette.
  2. Adjust the barrel adjuster:
    • Fine-tune the cable tension by turning the barrel adjuster located at the rear derailleur or the shifter.
    • Turning the barrel adjuster counterclockwise increases cable tension, while turning it clockwise decreases tension.
  3. Check shifting across the entire range:
    • Shift through the gears while spinning the rear wheel. Listen for any hesitation or skipping in the shifting process.
    • If the derailleur is slow to respond or if shifting feels sluggish, fine-tune the barrel adjuster until you achieve smooth transitions.
  4. Test the front derailleur interaction:
    • Ensure that the front derailleur is shifting properly between chainrings. The GRX RD-RX820 is designed to work in harmony with Shimano’s 2x front drivetrains, but occasional adjustment may be needed.

Maintenance of the GRX RD-RX820 (12-speed 2x) Rear Derailleur

Maintaining the GRX RD-RX820 ensures it continues to deliver top-notch performance, especially in demanding gravel and off-road conditions. Regular maintenance involves checking for wear and tear, cleaning the derailleur, and lubricating moving parts.

Routine Maintenance:

  1. Clean the derailleur:
    • Wipe down the derailleur with a clean rag after each ride, especially after riding in muddy or wet conditions. Use a degreaser to remove any built-up grime and dirt that could impair the performance.
  2. Inspect the jockey wheels:
    • Check the jockey wheels for wear. Over time, the teeth on the jockey wheels can become worn, which may lead to poor shifting. If necessary, replace the jockey wheels.
  3. Check for derailleur hanger alignment:
    • Ensure that the derailleur hanger is not bent or misaligned. A bent hanger can cause poor shifting and even damage the derailleur. Use a derailleur hanger alignment tool to make adjustments as needed.
  4. Lubricate moving parts:
    • Apply lubricant to the pivot points of the derailleur to keep the moving parts running smoothly. Avoid over-lubricating, as excess lubricant can attract dirt and grime.

Troubleshooting Common Issues with the GRX RD-RX820

While the GRX RD-RX820 is designed for reliability, issues can sometimes arise during use. Here are some common problems and how to troubleshoot them.

1. Skipping Gears or Hesitant Shifting:

  • Cause: This could be due to improper cable tension or a worn-out chain.
  • Solution: First, adjust the barrel adjuster to fine-tune cable tension. If the issue persists, check the chain for wear and replace it if necessary.

2. Derailleur Failing to Shift to Larger Cogs:

  • Cause: Insufficient B-tension or incorrectly set limit screws.
  • Solution: Adjust the B-screw to ensure the derailleur has the correct clearance from the cassette. Also, check the high limit screw to ensure the derailleur can shift into the largest cog.

3. Chain Dropping or Skipping When Shifting:

  • Cause: Misaligned derailleur hanger or incorrect derailleur installation.
  • Solution: Check the derailleur hanger alignment and ensure the derailleur is installed properly. Reinstall or adjust as needed.

Customization and Optimization for Better Performance

The GRX RD-RX820 can be customized to improve performance, especially for gravel and adventure riding. A few adjustments and upgrades can take your ride to the next level.

1. Upgrade to a Wider Cassette:

  • For riders looking for more range on steep climbs or rough terrain, consider upgrading to a wider cassette compatible with the RD-RX820. Shimano offers cassettes ranging from 11-34T to 11-40T, providing a better gear range.

2. Optimize Chain Length:

  • Customizing the chain length ensures smooth shifting and prevents the chain from dragging in larger gears. Adjust the chain to the ideal length for your drivetrain to maximize shifting performance.

3. Use High-Quality Chains and Cables:

  • The quality of the chain and cables can significantly affect shifting performance. For the best results, use Shimano’s 12-speed chains and high-quality cables that are designed to work seamlessly with the GRX RD-RX820.

Comparing the GRX RD-RX820 with Other Shimano Rear Derailleurs

When choosing a rear derailleur for your gravel bike or adventure setup, it’s essential to understand the differences between models. Here, we compare the GRX RD-RX820 with Shimano’s RD-M8000 (Deore XT) and RD-RX810 (GRX) rear derailleurs.

GRX RD-RX820 vs. RD-M8000 (Deore XT):

  • Target Audience: RD-RX820 is designed for gravel and adventure cyclists, while RD-M8000 is better suited for mountain bikers.
  • Shifting Performance: The RD-RX820 offers a more refined shifting experience under load, thanks to its specifically tuned design for gravel riding.
  • Durability: RD-RX820 features a more rugged build, ideal for rougher terrain, while the RD-M8000 is designed for mountain biking.

GRX RD-RX820 vs. GRX RD-RX810:

  • Weight: The RD-RX820 is slightly heavier due to its larger cassette capacity (up to 42T), making it better for extended gravel climbs.
  • Shifting Technology: The RD-RX810 is lighter and more streamlined, ideal for fast-paced gravel racing, while the RD-RX820 is more geared toward mixed-terrain and touring rides.

Compatibility with Other Drivetrain Components

The Shimano GRX RD-RX820 is designed to work seamlessly with Shimano’s 12-speed 2x drivetrains. It is fully compatible with Shimano’s GRX shifters, cassette, and chain. However, it’s important to note that compatibility with other drivetrain components, such as SRAM or Campagnolo, may require special adapters or adjustments.

Key Compatibility Notes:

  • Shimano 12-speed cassette: The GRX RD-RX820 is designed to work with Shimano’s 12-speed cassettes, ensuring precise gear shifting.
  • Shimano GRX 2x shifters: Best performance is achieved when paired with Shimano GRX 2x shifters, although it may be compatible with other Shimano 12-speed shifters.
  • Chain: Use Shimano 12-speed chains for optimal shifting accuracy and durability.

In conclusion, the Shimano GRX RD-RX820 rear derailleur is an excellent choice for gravel and adventure riders looking for performance, durability, and smooth shifting under rough conditions. With proper installation, regular maintenance, and careful adjustments, the RD-RX820 will provide reliable service for many rides to come.