How to Install, Adjust, and Maintain the Shimano RD-3400 Rear Derailleur

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in Rear Derailleur, Shimano, Sora

The Shimano RD-3400 [paid link] is a rear derailleur designed for Shimano’s Sora groupset, commonly found on entry-level [paid link] road bikes. Proper installation and adjustment are essential for achieving crisp, accurate shifts.

In this guide, we’ll walk through the step-by-step process of installing, adjusting, and maintaining your Shimano RD-3400 [paid link] to keep your drivetrain running smoothly.

Tools Required [paid links]

Step-by-Step Installation of the Shimano RD-3400 Rear Derailleur

1. Preparing the Bike for Installation

Before installing the derailleur, shift the chain onto the smallest chainring and smallest rear cog. This relieves tension and makes installation easier.

  • Inspect the derailleur hanger for alignment. If it’s bent, use a derailleur hanger alignment tool to straighten it.
  • Clean the derailleur mounting area on the frame to remove dirt and debris.

2. Mounting the Rear Derailleur

  • Position the derailleur’s B-knuckle onto the derailleur hanger.
  • Use a 5mm Allen wrench [paid link] to tighten the mounting bolt to Shimano’s recommended torque (usually 8–10 Nm).
  • Ensure the derailleur is securely attached and moves freely.

3. Installing the Chain

  • Thread the chain through the jockey wheels (guide pulley at the top, tension pulley at the bottom).
  • Use a chain tool to connect the chain with the appropriate length.
  • Shift through the gears to confirm the chain runs smoothly.

4. Connecting the Shift Cable

  • Insert the shift cable into the derailleur’s cable anchor bolt and pull it taut.
  • Secure the cable by tightening the bolt with a 5mm Allen wrench [paid link].
  • Trim excess cable and use a cable end cap to prevent fraying.

Adjusting the Shimano RD-3400 for Smooth Shifting

1. Setting the High Limit Screw (H-Screw)

The H-limit screw prevents the derailleur from shifting the chain past the smallest cog.

  • Locate the H-screw (usually marked with an “H”).
  • Turn it clockwise to move the derailleur inward or counterclockwise to move it outward.
  • Ensure the jockey wheel aligns with the smallest cog when in the highest gear.

2. Setting the Low Limit Screw (L-Screw)

The L-limit screw prevents the chain from overshooting the largest cog.

  • Shift to the largest cog and observe the derailleur’s alignment.
  • Turn the L-screw clockwise to move the derailleur outward or counterclockwise to move it inward.
  • The jockey wheel should align precisely with the largest cog.

3. Adjusting B-Screw for Proper Chain Tension

The B-tension screw controls the distance between the top jockey wheel and the cassette.

  • Shift into the largest cog and observe the gap between the upper jockey wheel and the cassette.
  • Turn the B-screw clockwise to increase the gap or counterclockwise to reduce it.
  • Maintain a gap of 5–6mm for optimal shifting performance.

4. Fine-Tuning Indexing with Barrel Adjuster

  • Shift through the gears to check for any hesitation or skipping.
  • Use the barrel adjuster near the shifter to make micro-adjustments:
    • Turn it counterclockwise if the derailleur is not shifting up smoothly.
    • Turn it clockwise if the derailleur hesitates to shift down.

Routine Maintenance for the Shimano RD-3400

1. Cleaning the Rear Derailleur

  • Use a degreaser and a clean rag to wipe down the derailleur.
  • Remove any built-up grime from the jockey wheels.
  • Avoid using high-pressure water, as it can force dirt into the pivots.

2. Lubricating the Moving Parts

  • Apply a small amount of light lubricant to the pivot points.
  • Spin the derailleur through the gears to distribute the lubricant.
  • Wipe off excess oil to prevent dirt buildup.

3. Inspecting for Wear and Damage

  • Check the jockey wheels for excessive wear and replace if needed.
  • Inspect the shift cable for fraying or corrosion.
  • Ensure the derailleur hanger remains straight, as a misalignment affects shifting quality.

Common Shimano RD-3400 Rear Derailleur Problems and Solutions

1. Shifting Feels Sluggish or Delayed

Cause: Dirty cables or lack of lubrication.
Solution: Clean and lubricate the cables, ensuring smooth movement.

2. Chain Skips Over Gears

Cause: Incorrect indexing or worn cassette.
Solution: Adjust the barrel adjuster and check for cassette wear.

3. Chain Drops When Shifting to Largest Cog

Cause: L-limit screw not properly set.
Solution: Adjust the L-screw so the jockey wheel aligns with the largest cog.

4. Noisy Shifting Between Gears

Cause: Misaligned derailleur hanger.
Solution: Use a derailleur hanger alignment tool to correct alignment.

Conclusion

The Shimano RD-3400 [paid link] rear derailleur is an essential component of the Sora groupset, providing reliable shifting performance when properly installed and maintained. By following this guide, you can ensure smooth, consistent shifting while extending the lifespan of your derailleur.