Fixing Chain Drops on Gravel Bikes with Apex XPLR Rear Derailleurs

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Chain drops are a common issue that gravel bike riders face, particularly during rough terrain or high-intensity efforts. For riders using the SRAM Apex XPLR [paid link] rear derailleur, addressing this problem involves understanding its unique features and making specific adjustments. In this article, we’ll explore how to fix chain drops on gravel bikes equipped with the Apex XPLR rear derailleur, providing step-by-step guidance on installation, adjustments, troubleshooting, and optimization.

Overview of the SRAM Apex XPLR Rear Derailleur

The SRAM Apex XPLR rear derailleur is specifically designed for gravel and adventure bikes. It features a long cage for extended gear ranges, allowing for smooth shifting over variable terrain. Its architecture includes SRAM’s Exact Actuation technology, which delivers precise, responsive shifts with minimal effort. Despite its durable construction and gravel-ready features, it’s important to properly adjust and maintain the derailleur to prevent chain drops and ensure consistent performance.

Tools Required

  • 5mm Allen wrench
  • 4mm Allen wrench
  • Screwdriver (for limit screws)
  • Torque wrench
  • Chain checker tool
  • Chain lube
  • Cable cutter
  • Lubricant for derailleur pivot points
  • Clean rag

Installation of the SRAM Apex XPLR Rear Derailleur

Correct installation of the SRAM Apex XPLR rear derailleur is essential for smooth operation and preventing chain drops. Follow these steps for proper installation:

  1. Mount the derailleur hanger: Ensure that the derailleur hanger is straight and aligned. If it’s bent or misaligned, it can cause the derailleur to shift incorrectly, increasing the risk of chain drops.
  2. Attach the derailleur: Use a 5mm Allen wrench to attach the derailleur to the derailleur hanger. Tighten the bolt securely, but be cautious not to over-tighten and damage the hanger.
  3. Install the chain: Thread the chain through the derailleur and make sure it runs smoothly across the jockey wheels. Check the chain’s condition and length to ensure it’s not too long or too short.
  4. Set the derailleur cable: Route the shift cable through the appropriate housing and attach it to the derailleur using the anchor bolt. Make sure the cable is properly tensioned before securing it.
  5. Check the derailleur alignment: After installation, manually shift through the gears to verify that the derailleur moves freely and that the chain engages properly with each cog.

Adjusting the Apex XPLR Derailleur to Prevent Chain Drops

Once installed, it’s important to fine-tune the Apex XPLR rear derailleur to avoid chain drops, especially when riding on rough terrain.

Limit Screw Adjustment

  1. Adjust the high-limit screw: Use a 2.5mm Allen wrench to fine-tune the high-limit screw. This screw prevents the chain from overshooting the smallest cog. Set the screw so that the derailleur stops just before the chain reaches the smallest cog.
  2. Adjust the low-limit screw: Similarly, adjust the low-limit screw to prevent the chain from falling off the largest cog. Set the screw so that the derailleur stops just before the chain could drop.

B-Tension Screw Adjustment

The B-tension screw controls the distance between the derailleur’s jockey wheels and the cassette cogs. If this distance is too large, it can cause chain misalignment and lead to drops.

  1. Check the gap: Shift the chain to the largest cog and measure the gap between the derailleur’s upper jockey wheel and the largest cog. Ideally, the gap should be around 6-8mm.
  2. Adjust the B-tension screw: Use a 4mm Allen wrench to adjust the B-tension screw. Tighten or loosen it to achieve the proper gap. This will ensure smoother shifting and reduce the risk of chain drops.

Cable Tension Adjustment

Proper cable tension is crucial for ensuring that the derailleur shifts accurately. If the cable is too loose, it can cause delayed shifts, which increases the likelihood of a chain drop.

  1. Shift to the smallest cog: Shift to the smallest cog on the rear cassette and check for smooth shifting.
  2. Adjust the barrel adjuster: Use the barrel adjuster on the rear derailleur or shifter to fine-tune the cable tension. Tighten the barrel adjuster if the derailleur is not shifting up to larger cogs. Loosen it if the derailleur is overshooting the larger cogs.

Chain Length and Compatibility

A common cause of chain drops is improper chain length. Ensure that the chain is long enough to accommodate the full range of gears, but not so long that it allows excessive slack.

  1. Check chain length: Shift the bike to the largest chainring and the largest cog. The rear derailleur should be able to accommodate this gear combination without overstretching. If the derailleur appears overstretched, it may indicate that the chain is too short.
  2. Adjust chain length: If necessary, remove links from the chain to shorten it or add links if it’s too short. This will ensure the derailleur can handle the full range of gears without risking chain drops.

Troubleshooting Common Chain Drop Issues with the Apex XPLR Rear Derailleur

Even with proper adjustments, issues can sometimes arise that lead to chain drops. Below are common problems and how to fix them:

1. Skipping or Dropping the Chain on Rough Terrain

  • Cause: This often occurs if the derailleur is not properly adjusted, especially the B-tension screw. If the jockey wheel is too far from the cassette, the chain can derail.
  • Fix: Recheck and adjust the B-tension screw, ensuring the jockey wheel is correctly positioned.

2. Chain Drops When Shifting to the Smallest Cog

  • Cause: If the high-limit screw is not properly adjusted, the chain can overshoot the smallest cog.
  • Fix: Adjust the high-limit screw to prevent the derailleur from moving too far inward.

3. Chain Drops When Shifting to the Largest Cog

  • Cause: A misadjusted low-limit screw can cause the chain to fall off the largest cog.
  • Fix: Adjust the low-limit screw to stop the derailleur at the correct point and prevent the chain from dropping.

4. Chain Rub or Poor Shifting Performance

  • Cause: This could be due to poor cable tension, a misaligned derailleur hanger, or a worn-out chain.
  • Fix: Check the derailleur hanger alignment, adjust cable tension, and replace the chain if it shows signs of wear.

Optimizing the Apex XPLR Rear Derailleur for Better Performance

For enhanced performance, consider these adjustments and maintenance practices:

Regular Lubrication

Lubricating the derailleur pivots will help reduce friction and improve shifting performance. Use a light oil or specific bicycle lubricant to ensure smooth movement.

Cleanliness

Keep the derailleur and the entire drivetrain clean by regularly wiping down the derailleur and chain after rides, especially after riding in muddy or wet conditions. This prevents dirt and debris from causing friction or damaging components.

Upgrade to a Better Chain

If you frequently experience chain issues despite proper derailleur setup, consider upgrading to a higher-quality chain that’s more resistant to wear and stretch.

Comparison with Similar Models

When comparing the SRAM Apex XPLR to other gravel-specific rear derailleurs, such as the Shimano GRX or the SRAM Rival XPLR, the Apex XPLR stands out due to its relatively lightweight design and excellent compatibility with wide-range cassettes. While the GRX features a clutch system to reduce chain slap, the Apex XPLR achieves smooth, quiet shifting through its unique design and precise actuation. Riders looking for a durable and low-maintenance system for gravel riding often find the Apex XPLR a great value.

Compatibility with Other Drivetrain Components

The SRAM Apex XPLR rear derailleur is designed to work seamlessly with other SRAM 1x drivetrains, especially when paired with SRAM’s XG cassettes and Rival or Force shifters. It’s important to ensure that all components in the drivetrain are compatible with the 1x system to prevent any issues with chain drop or poor shifting performance.