Shifting Problems Map: Symptom to Fix
Match your symptom to the most likely cause and the specific fix. Most rear derailleur issues come down to cable tension or limit screws; most chain noise comes down to lubrication or wear. In 80% of cases, a 1/4 turn of the barrel adjuster resolves the problem.
| Symptom | Most Likely Cause | Fix |
|---|
| Chain skips 1-2 gears | Cable tension off | Barrel adjuster 1/4 turn CCW |
| Chain skips under load only | Worn chain + cassette | Replace chain (+ cassette if 0.75%+) |
| Clicking in specific gears | Indexing slightly off | Barrel adjuster 1/4 turn |
| Won't reach biggest cog | Low limit screw too tight | L screw 1/4 turn CCW |
| Won't reach smallest cog | High limit screw too tight | H screw 1/4 turn CCW |
| Ghost shifting under load | Bent derailleur hanger | Straighten or replace hanger |
| Slow / delayed shifting | Contaminated cables | Replace inner cables + housing |
| Chain drops off cassette | Limit screws wrong | Tighten appropriate limit screw |
| Noise in all gears | Dry or worn chain | Clean, lube, or replace chain |
| Front chain rub | FD height / angle / trim | Adjust FD or use trim position |
The Barrel Adjuster: The Most Useful Tool on Your Bike
The barrel adjuster is a small threaded cylinder where the cable enters the rear derailleur (or at the shifter). Turning it counterclockwise increases cable tension, pulling the derailleur toward bigger cogs. Clockwise decreases tension, allowing the spring to pull toward smaller cogs. A 1/4 turn at a time is enough. This single adjustment fixes 80% of all shifting problems. Learn to use it mid-ride without tools, so you can keep riding while sorting out a noisy gear.
When to Replace Chain vs Cassette vs Both
Chain at 0.5% wear (chain checker shows 0.5): replace chain only (15 to 30 USD). Chain at 0.75% or more: replace chain AND cassette (chain 15 to 30 USD + cassette 30 to 80 USD), because they have worn together. If you put a new chain on a worn cassette, it will skip under load. Chainrings last 2 to 3 times longer than cassettes. Replace chainrings only when teeth are visibly hooked or shark-fin shaped.
Mechanical vs Electronic Shifting Problems
Mechanical (cable-actuated): most problems come from cable stretch, contamination, or a bent hanger. Fix with the barrel adjuster, cable replacement, or hanger alignment. Electronic (Shimano Di2, SRAM AXS, Campagnolo EPS): no cables to stretch. Problems come from firmware, battery, or a crashed derailleur. Reset and re-pair first. If that fails, micro-adjust in the app (Shimano E-Tube, SRAM AXS app). Electronic rarely needs physical adjustment, but a bent hanger affects electronic shifting too.
The B-Tension Screw: The Forgotten Adjustment
The B-tension screw controls the gap between the upper jockey wheel and the cassette. Correct gap: 5 to 6 mm when in the biggest cog. Too close: noise, chain jam risk. Too far: slow, hesitant shifting especially in bigger cogs. Check after changing cassette size (for example, from 11-28 to 11-34), because a bigger cassette needs more B-tension. The screw is at the back of the derailleur where it meets the hanger.
Hanger Alignment: The Most Overlooked Fix
A bent derailleur hanger is responsible for an estimated 30 to 40 percent of all rear shifting complaints, yet most riders never check it. The hanger is the small aluminum bracket that the rear derailleur bolts onto. It is intentionally weaker than the frame so that it deforms instead of cracking the frame in a crash. Even leaning the bike against a wall, dropping it on the drive side, or hitting a rock can bend the hanger 1 to 3 mm. View the derailleur from directly behind the bike: the parallelogram body should be perfectly parallel to the cassette cogs. If the lower jockey wheel angles inward or outward relative to the upper jockey wheel, the hanger is bent. A derailleur alignment gauge (DAG, around 60 to 100 USD) screws into the derailleur mount and rotates around the wheel, letting you measure and correct the bend in three planes. A bike shop alignment service costs 10 to 25 USD and takes 10 minutes.
Cable and Housing Replacement: Step-by-Step
Inner cables stretch and fray; outer housing accumulates grit and bends inside. Both cause slow, sticky, or unpredictable shifting after about 12 to 18 months of regular riding. Replacement: (1) Shift to the smallest cog so cable tension is lowest. (2) Loosen the cable clamp bolt on the derailleur with a 4 or 5 mm Allen key. (3) Pull the cable out at the shifter end (look inside the shifter for the cable head). (4) Cut new housing to match old lengths, file the ends square, install ferrules at each end. (5) Route new inner cable through housing, clamp at the derailleur. (6) Set tension with the barrel adjuster and pull cable taut with pliers before final clamp tightening. (7) Trim excess cable, install end cap. Quality replacement cost: 15 to 30 USD parts. Use Shimano Optislick or Jagwire Pro Slick for the smoothest action. Wax-impregnated housings (Jagwire LEX) reduce friction by 20 to 30 percent compared with stock housings.
Drivetrain Compatibility: Mixing Components
Mixing components across brands and generations is risky but sometimes works. Shimano 10-speed: cassette, chain, shifter and derailleur must match (Shimano 10-speed road and MTB are NOT compatible due to different cable pull ratios). Shimano 11-speed road and 11-speed MTB are also not interchangeable. SRAM 1x11 and 1x12 each use different cable pull (Exact Actuation vs X-Actuation), so derailleurs and shifters must be from the same family. SRAM 12-speed Eagle MTB uses yet another ratio. Campagnolo is its own ecosystem and cross-compatibility with Shimano or SRAM is generally not possible. Chains are partially cross-compatible: Shimano 11-speed road chains work on SRAM 11-speed cassettes. KMC chains often match multiple brands. When in doubt, check the manufacturer's compatibility chart. The wrong combination causes constant ghost shifting, skipping, or shifters that simply do not work with the derailleur.
Common Drivetrain Tools to Own
For home shifting maintenance, a basic kit costs around 60 to 120 USD: (1) chain checker (Park Tool CC-3.2, 12 USD): measures chain wear. (2) chain breaker (Park Tool CT-3.3, 25 USD): removes and installs chains. (3) cassette lockring tool and chain whip (Park Tool FR-5G + SR-12.2, 30 USD): removes the cassette. (4) Allen keys, 3 to 8 mm (10 USD): every derailleur adjustment. (5) cable cutters (Park Tool CN-10, 30 USD): cuts inner cables and housing cleanly without crushing or fraying. Optional but useful: derailleur alignment gauge (60 to 100 USD) and a torque wrench (40 USD) for accurate clamp bolt tightening.
Diagnosis by Sound: What Is the Bike Telling You?
A rhythmic tick-tick once per pedal stroke (one per revolution): something on the crank is loose. Check chainring bolts, pedal threads, crank arm bolts. A tick-tick-tick faster than crank revolution (multiple times per second when pedaling): chain touching the front derailleur or adjacent cog. Adjust the FD or barrel adjuster. A grinding or scraping noise: dry or worn chain. Lube first, replace second. A chattering or buzzing in only some gears: indexing is off in those gears specifically. 1/4 turn of the barrel adjuster. A click from the seat post or saddle area that LOOKS like a drivetrain issue: tighten the seat clamp and saddle rails. Many drivetrain noises are actually somewhere else on the bike entirely.
Wet Weather Shifting Care
Rain and grit are the fastest way to ruin a drivetrain. After every wet ride: rinse the chain, cassette and derailleur with clean water (low pressure, no pressure washer). Dry with a rag. Re-lube the chain with a wet-conditions lube (Squirt Wet, Muc-Off Wet). Pay attention to the cable entry at the rear derailleur: water and grit collect there and accelerate cable friction. Replace cables every 6 to 9 months instead of 12 to 18 if you ride in rain regularly. A drivetrain cover for transport (12 to 20 USD) prevents road salt from car-rack rides during winter. Storing the bike with a lubed chain prevents rust from forming overnight in humid garages.
Long Cage vs Short Cage Derailleurs
The derailleur cage is the arm holding the jockey wheels. Short cage: smaller capacity, lighter, snappier shifts. Designed for road bikes with smaller cassette ranges (11-28 or smaller). Long cage: larger capacity, slower shifts, can handle 11-34, 11-36 or wider cassettes plus front double or triple chainrings. Putting a short-cage road derailleur on a wide-range cassette (11-34 with a short cage Ultegra) causes the cage to bottom out and snap. Always check the maximum cassette size and total capacity of your derailleur against your gearing. Shimano and SRAM publish max sprocket and total capacity numbers for every derailleur model.
Chain Length: Why It Matters for Shifting
A chain that is too long sags in the small-small combination and slaps the chainstay. A chain that is too short cannot reach the biggest cog with the big chainring (big-big), and can snap the rear derailleur cage. Setting chain length: shift to big chainring and biggest cog WITHOUT routing through the derailleur. Add 2 full links (one inner pair plus one outer pair). Route through the derailleur and join with a quick link. Verify by shifting through extreme gears: small-small should not sag and should not let the cage flip forward of vertical. Big-big should not over-tension. Replace the chain every 1500 to 3000 km (road) or 500 to 1500 km (MTB). When installing a quick link, mount it on the bottom of the chain run so the lever points away from rotation; some quick links are directional (KMC arrows, Shimano dots).
Indexing Step-by-Step: Setting Up a New Derailleur
Setting up a new mechanical rear derailleur from scratch: (1) Bolt the derailleur to the hanger, 8 to 10 Nm. (2) Set the H limit: shift to smallest cog, turn H screw until the upper jockey wheel sits directly under the smallest cog when viewed from behind. (3) Run the cable through housing, route through the cable stops on the frame, clamp at the derailleur with no slack but no tension. Pull cable taut with pliers as you tighten the clamp to 5 to 7 Nm. (4) Set the L limit: with the chain off, push the derailleur inward until the upper jockey wheel sits directly under the biggest cog. Turn L screw to set this position. (5) Install the chain, sized correctly. (6) Set B-tension: in the biggest cog, adjust the B screw until there is 5 to 6 mm of gap between the top of the cog and the upper jockey wheel. (7) Fine-tune with the barrel adjuster: pedal and shift one click at a time; if shifting to bigger cogs is sluggish, increase tension (CCW); if it overshoots, decrease (CW). Verify across all 11 or 12 cogs without skipping or hesitating.
Internal Cable Routing: Modern Bike Challenges
Modern road and gravel bikes route cables internally through the frame. Internal routing looks clean but creates two problems: cable replacement is harder, and friction is higher because the cable has more bends. For replacement, look for cable guides at the cable entry ports; some frames have a guide tube already installed (Trek). If not, fish a thin nylon string or magnet through the frame. Many modern brands ship bikes with magnetic cable insertion tools. Keep the old housing in place during inner cable replacement so you can pull the new cable through. For full housing replacement, consider taking the bike to a shop unless you have done it before; pulling housing out of internal routing can leave you with no way to get it back in. Cable replacement on internally routed bikes takes 30 to 60 minutes vs 15 minutes for external routing.
Electronic Shifting Troubleshooting
Shimano Di2, SRAM AXS, and Campagnolo EPS eliminate cable problems but introduce new ones. Common electronic issues: (1) Battery dead or low: the front derailleur usually fails first, then the rear, as a safety hint to charge. (2) Firmware out of date: the app (E-Tube Project, AXS App, MyCampy) will prompt updates. (3) Lost pairing between shifters and derailleurs: re-pair using the function button on the rear derailleur (Shimano) or the AXS button (SRAM). (4) Micro-adjust drift: even electronic groupsets need micro-adjustment after a wheel change or hanger straightening. Tap the micro-adjust button on the shifter to shift the derailleur half a cog at a time without changing gear. (5) Crash damage: electronic derailleurs are tougher than mechanical but still need hanger alignment after a crash. None of the electronic systems can compensate for a bent hanger; alignment is still the first thing to check.
Related Bike Tools
Frequently asked questions
Why is my bike chain skipping gears?
In 80% of cases, cable tension is slightly off. Turn the barrel adjuster on the rear derailleur 1/4 turn counterclockwise (increases tension). If skipping continues, check chain wear with a chain checker. At 0.5% or more, replace the chain. If skipping only under hard pedaling, both chain and cassette are likely worn.
How do I adjust my rear derailleur?
Three adjustments: (1) Barrel adjuster for cable tension (1/4 turns, most common fix). (2) H and L limit screws for range of movement (prevent chain dropping). (3) B-tension screw for jockey wheel gap (5 to 6 mm from biggest cog). Start with barrel adjuster. Only touch limit screws if the chain cannot reach the biggest or smallest cog.
What causes ghost shifting on a bike?
A bent derailleur hanger (especially after a crash) is the most common cause. The hanger bends 1 to 2 mm, shifting the indexing under load. Other causes: sticky cable housing, loose cable clamp, or worn chain. Hanger alignment costs 10 to 20 USD at a bike shop and fixes most ghost shifting immediately.
How often should I replace my bike chain?
Every 1500 to 3000 km for road bikes, 500 to 1500 km for mountain bikes (mud and grit wear chains faster). Use a chain checker monthly. Replace at 0.5% wear. This 15 to 30 USD replacement prevents an 80+ USD cassette replacement. A well-maintained chain that is replaced on time extends cassette life by 2 to 3 times.
Why does my front derailleur rub?
Chain rub on the front derailleur is normal in extreme gear combinations (big-big, small-small). Use the trim function on your shifter (half-click) to adjust. If rub occurs in normal gears, check front derailleur height (1 to 3 mm above big chainring) and angle (parallel to chainrings from above).
Last updated: May 2026. Based on Shimano, SRAM and Campagnolo derailleur service guides.