The Shimano GRX RD-RX820 [paid link] rear derailleur is designed specifically for gravel and adventure cyclists. Part of Shimano’s GRX series, this model brings a blend of smooth shifting performance and durable construction, ideal for handling rough terrains. In this review, we’ll cover the key aspects of the GRX RD-RX820, including installation, maintenance, troubleshooting, and optimization tips.
Installation and Setup
Tools Required
- 5mm Allen wrench
- 3mm Allen wrench
- Torque wrench
- Screwdriver (for B-limit screw adjustments)
- Chain tool
- Shimano GRX RD-RX820 derailleur hanger (if needed)
Step-by-Step Installation
- Remove the Old Derailleur:
If you’re replacing an existing derailleur, start by removing it with a 5mm Allen wrench. Detach the derailleur from the derailleur hanger and unhook the chain from the derailleur. - Install the GRX RD-RX820 Derailleur:
Position the derailleur on the derailleur hanger and secure it using the 5mm Allen wrench. Make sure it’s tightly fitted but avoid over-tightening. - Install the Chain:
Loop the chain through the derailleur jockey wheels and ensure it’s properly threaded through the cassette. You may need to adjust the chain length based on your gear setup. - Adjust the B-Limit Screw:
Using a screwdriver, adjust the B-limit screw on the derailleur to ensure the jockey wheels clear the cassette teeth when the chain is on the smallest cog. - Set Up the Gear Cable:
Attach the gear cable to the derailleur and adjust its tension using the barrel adjuster. This will help ensure smooth shifting across all gears. - Test Shifting:
After installation, shift through all the gears to ensure smooth transitions. Make adjustments to the derailleur hanger alignment if necessary.
Adjustment and Maintenance
Fine-Tuning Shifting Performance
To ensure smooth and precise shifting, the Shimano GRX RD-RX820 needs to be properly adjusted. Begin by checking the alignment of the derailleur hanger. A misaligned hanger can lead to poor shifting performance or even damage to the derailleur.
- Rear Derailleur Alignment:
Use a derailleur hanger alignment tool to ensure that the hanger is straight. If the derailleur is not aligned properly, the shifting will be sluggish and inconsistent. - Cable Tension:
The cable tension plays a key role in achieving smooth shifting. Too much tension can cause the derailleur to overshoot or shift roughly, while too little tension can result in skipped gears. Adjust the barrel adjuster on the shifter or derailleur to fine-tune the cable tension. - Limit Screw Adjustment:
The GRX RD-RX820 comes with two limit screws (H and L) that control the movement of the derailleur. Adjust the high (H) and low (L) limit screws to ensure the derailleur moves correctly across the cassette and prevents the chain from falling off the gears.
Maintenance Tips for Longevity
- Cleaning and Lubing:
Regularly clean the derailleur and jockey wheels to remove dirt, debris, and grit [paid link], which can affect shifting performance. Lubricate the jockey wheels and pivot points with a light oil or bike-specific lubricant. - Inspect for Wear:
Over time, the jockey wheels, derailleur body, and other moving parts can wear out. Check for cracks, excessive wear, or bent parts. Replacing these components as necessary will prolong the life of the derailleur. - Chain Maintenance:
A clean and properly lubricated chain ensures the derailleur operates smoothly. Check for chain wear and replace it if needed. A worn chain can cause poor shifting and may even damage the derailleur.
Troubleshooting Common Set-Up Issues
Shifting Is Sluggish or Inconsistent
- Check Cable Tension: If shifting feels sluggish or inconsistent, the most common culprit is incorrect cable tension. Adjust the barrel adjusters to fine-tune the tension for smooth gear transitions.
- Misaligned Derailleur Hanger: A misaligned derailleur hanger can cause poor shifting performance, particularly when the derailleur is moving across the cassette. Use a derailleur hanger alignment tool to check and straighten it.
- Dirty Components: Dirt and debris can clog the derailleur mechanism. Clean the derailleur and jockey wheels regularly to maintain smooth operation.
Chain Dropping or Skipping
- Limit Screws Adjustment: If the chain is dropping or skipping, check the limit screws to ensure the derailleur is properly positioned within the gear range. Incorrect adjustment can lead to the chain falling off the cassette.
- Chain Wear: A worn chain can cause skipping, as it may not mesh well with the teeth of the cassette. Measure the chain wear and replace it if necessary.
Customization and Optimization for Better Performance
The GRX RD-RX820 is designed to deliver reliable shifting performance on gravel and mixed-terrain rides. However, there are several ways to optimize its performance for different riding styles:
Upgrade Your Chainring
Switching to a more gravel-specific chainring can enhance shifting under load and improve overall drivetrain performance. The GRX RD-RX820 works well with a variety of 10-51t or 11-40t cassettes, but experimenting with different chainring sizes can optimize your ride based on your terrain.
Adjust for More Precise Shifting
Fine-tuning the B-limit screw can make the derailleur work more efficiently when navigating rougher terrain. By ensuring a closer fit between the jockey wheels and the cassette, you can reduce noise and improve shifting precision.
Consider a Shorter Cage
If you’re using a smaller cassette and are looking for quicker shifts, consider switching to a short cage version of the GRX RD-RX820. This modification reduces the derailleur’s total capacity and can make for faster, snappier shifting, especially in competitive settings.
Comparison with Similar Models
The Shimano GRX RD-RX820 rear derailleur competes with several models designed for gravel and adventure bikes. Here’s a quick comparison with the RD-RX810 and RD-RX400:
- Shimano GRX RD-RX810 [paid link]: The RD-RX810 is a more affordable option with slightly less emphasis on weight savings and durability under extreme conditions. While it offers reliable performance for gravel riding, the RD-RX820 is a more refined, durable option that handles rougher, off-road conditions better.
- Shimano GRX RD-RX400: The RD-RX400 is Shimano’s entry-level gravel derailleur, offering decent performance at a lower price point. It lacks the high-end features of the RD-RX820, such as the advanced clutch mechanism for chain stability, making the RX820 the preferred choice for serious gravel riders.
Understanding Compatibility with Other Drivetrain Components
The Shimano GRX RD-RX820 is compatible with 11-speed Shimano road and gravel drivetrains. When setting up a complete drivetrain, it’s important to ensure compatibility with the cassette, chain, and shifters.
- Cassette Compatibility: The RD-RX820 supports 11-speed cassettes in the 11-34t to 11-40t range. It is essential to pair this derailleur with a cassette within this range for smooth shifting performance.
- Shifter Compatibility: This derailleur works best with Shimano’s GRX series shifters. However, it is also compatible with Shimano 105 and Ultegra 11-speed shifters, provided the correct gear ratios are used.
By ensuring proper component compatibility, you can achieve seamless performance across all gear ranges, especially when riding on uneven, gravelly surfaces.
Conclusion
The Shimano GRX RD-RX820 rear derailleur is an excellent choice for gravel and adventure cyclists looking for a durable, smooth-shifting option. Its solid construction, precision, and adaptability make it ideal for demanding conditions. Whether you’re installing it for the first time or maintaining an existing setup, proper adjustment and maintenance are crucial to ensuring optimal performance. By taking advantage of its customization options and understanding its compatibility with other components, you can maximize the lifespan and effectiveness of your drivetrain.