Video summary

How to Adjust a Rear Derailleur – Limit Screws & Indexing

Main summary

Key takeaways

Product Review

Product/Topic Reviewed

A mechanical rear derailleur adjustment procedure (Park Tool Company video) covering:

  • Limit screws (H & L)
  • Indexing using the barrel adjuster
  • B-screw (body angle) adjustment

The goal is to restore proper shifting.

Key Features / What the Video Covers

Rear Derailleur Function

The rear derailleur shifts the chain across rear cogs using a cable from an index shifter. The shifter’s clicks move the cable in predetermined increments.

Limit Screws (H and L)

  • Prevent the chain from moving too far inward/outward
  • Specifically avoids the chain entering spokes or the frame
  • H and L are set to control the derailleur’s travel limits

Indexing (Guide Pulley Alignment)

  • Uses the barrel adjuster (at the derailleur or shifter) so each shift click aligns with the correct cog.
  • There may be a range of acceptable barrel adjuster positions, not just one “perfect” setting.

B-Screw (B Screw / Body Angle)

  • Adjusts the spacing between the guide pulley (G pulley) and the cogs.
  • Checked with:
    • Chain on smallest front sprocket
    • And largest rear cog
  • Many road/MTB derailleurs target approximately ~5–6 mm gap, but the video recommends following manufacturer specifications.

Practical Test Method (Using Noise)

  • Excess noise indicates misadjustment—such as the chain rubbing or striking the next inboard cog.
  • Adjustments are made in small increments, typically:
    • Quarter-turn and half-turn steps depending on the screw/process.

Pros (Implied Benefits / Strengths)

  • A systematic process that works across “regardless of make or model” for mechanical rear derailleur adjustment.
  • Strong safety/protection logic:
    • Set H and L screws “too tight first,” then back out until correct—explicitly to prevent the derailleur from pushing the chain too far.
  • Noise-based diagnosis helps guide adjustments efficiently.
  • Clear emphasis on not confusing:
    • Shifter position vs limit screw position
    • (Resolved by adjusting/adding slack with the barrel adjuster.)
  • Includes verification steps beyond alignment, such as:
    • Checking cage movement under extra shifter pressure
    • Recommending a test ride

Cons / Limitations (Based on the Content)

  • Requires a repair stand and tools (e.g., screwdriver/hex keys) to pedal and verify shifting under load.
  • Some variability/uncertainty may exist:
    • Limit screws may be unmarked, requiring trial to identify H vs L
    • Some shifters may click multiple times per lever push, requiring you to listen for the correct single click
  • Mentions possible advanced troubleshooting if basic steps don’t resolve the issue (e.g., hanger issues).

User Experience / How It Feels to Follow

  • Step-by-step tuning with frequent checks:
    • Pedal while turning screws/adjusters
    • Shift one click at a time and listen/observe
  • Workflow improvements:
    • Adjust barrel slack before setting limits to avoid misinterpreting shift problems
    • Repeat across gears; correct by about ~quarter-turn when rubbing/noise appears
  • Ends with:
    • A test ride recommendation, since stand adjustments may differ under real drivetrain load

Comparisons Mentioned

  • No direct product-to-product comparisons.
  • Refers to “advanced troubleshooting and rear derailleur adjustment” as the next step if this guide doesn’t fix symptoms.
  • Notes variation by derailleur type/spec:
    • Road and mountain bikes generally target 5–6 mm, but exceptions exist per manufacturer.

All Unique Points Mentioned (Consolidated)

Common Symptoms

  • Shifting issues like:
    • Not reaching all gears
    • Making noises

Rear Derailleur / Shifter Relationship

  • Cable + housing link the shifter to the derailleur.
  • Index shifter clicks correspond to preset cable movement increments.
  • A spring pulls the derailleur outward, while the cable holds it in position.

Limit Screw Logic

  • Limit screws stop the derailleur from traveling too far inward/outward.
  • This protects against the chain entering spokes/frame.
  • The order emphasized is:
    • Set H first
    • Then set L after indexing

H Screw Notes & Procedure

  • Before adjusting H:
    • Shift to the front largest chainring (if applicable)
    • Shift rear to the smallest cog, continue clicking until no more clicks
  • If H is not allowing smallest-cog shifting:
    • Turn H counterclockwise a few turns, then adjust barrel adjuster clockwise as needed
  • To avoid confusion between shifter position and limit screw:
    • Add slack by turning the barrel adjuster clockwise
  • If H is unmarked:
    • Identify it by testing which screw causes derailleur movement in the expected direction
  • “Too tight then back out” method:
    • Tighten H by half-turn, listen for noise/rubbing
    • If noise occurs (chain rubbing the next inboard cog), loosen in small steps (quarter-turn) until noise disappears
    • If two settings are equally quiet, choose the tighter one
  • Note: overly tight limit screw can cause shifting to the next cog, but (per the video) it doesn’t damage the drivetrain

Indexing (Barrel Adjuster) Notes & Procedure

  • The barrel adjuster changes cable slack/alignment so each click matches a cog.
  • Use a normal cadence and shift only one index click at a time.
  • If one click shifts “too far” (e.g., two sprockets):
    • Correct it afterward with fine-tuning using the barrel adjuster.
  • Outside-range then back in method using noise:
    • Turn barrel adjuster CCW until excessive noise appears
    • Then turn CW by quarter-turn steps until noise is gone
  • Repeat across rear cogs one-by-one.
  • The largest cog shift is done later.
  • If outward shifting is slow, improve with another quarter-turn CW.

L Screw Notes & Procedure

  • Similar “too-tight-then-back-out” protection from chain traveling past the largest cog into spokes.
  • Steps:
    1. Shift to the next-to-largest front chainring (if applicable), then rear second-largest cog
    2. Shift to largest rear cog to determine if L is too tight/too loose/just right
    3. If the chain doesn’t shift: L is already too tight for this stage
    4. If shifting is slow or noisy: symptoms of too tight L
    5. If acceptable: tighten L half-turn, then loosen incrementally (quarter-turn) until it shifts quickly with no excessive noise

B-Screw Adjustment Notes

  • Check with chain on:
    • smallest front sprocket + largest rear cog
  • Target gap:
    • 5–6 mm for many road/MTB derailleurs
    • Follow manufacturer specs when available
  • If the B gap must increase: tighten B
  • If the B gap must decrease: loosen B
  • Significant B changes require re-checking indexing afterward.

Final Checks

  • With extra shifter pressure, the derailleur cage should not move inward.
  • Test ride recommended.
  • If problems remain:
    • adjust barrel or limit screws by another quarter turn
  • If still not correct:
    • consult advanced troubleshooting

Hanger Issues (Important Note)

  • If the hanger is bent, shifting won’t work well.
  • The video suggests watching a hanger alignment-specific video.

Speakers / Contributions

  • Calvin Jones (Park Tool Company): the main narrator/instructor.

Concise Verdict / Recommendation

If your mechanical rear shifting is off or noisy, follow this guide. It’s a practical, methodical approach:

  1. Set H
  2. Index with the barrel adjuster
  3. Set L
  4. Check B screw

Use noise and small incremental adjustments as the diagnostic signals. It’s recommended as a reliable baseline before moving on to advanced troubleshooting.

Original video