Bike gears slip when chain, cassette, or hub fail to mesh cleanly—most often from wear, misadjustment, contamination, cross-chaining, or wrong chain length.
You push on the pedals, the cranks lurch, and the rear wheel doesn’t match your effort. That jump is gear slip. It wastes power, rattles confidence, and can end a ride. The good news: the causes are few, the checks are simple, and the fixes are straight-ahead once you know where to look.
Why Do Bike Gears Slip? Common Scenarios
The same handful of faults keep showing up in home workshops and pro pits. The list below ranks the usual suspects and gives you a quick path to a diagnosis. You’ll spot patterns fast: worn parts skip under load, misaligned parts misplace the chain, and sticky parts react late.
| Likely Cause | Tell-Tale Symptom | Fast Check |
|---|---|---|
| Stretched/Worn Chain | Repeating skip on hard pedaling | Measure wear; match chain to cassette |
| Worn Cassette Or Chainring | Skips on a few specific cogs or a single ring | Inspect tooth profiles; test with fresh chain |
| Cable Tension Off | Shifts are late or overshoot one way | Quarter-turn at barrel; re-test under load |
| Limit Screws/B-Tension Mis-set | Chain hunts near ends of the cassette | Align jockey wheel to cogs; set pulley gap |
| Dirty Or Dry Drivetrain | Grindy sound; sluggish shifts | Clean, lube, and wipe excess |
| Freehub Pawls Slipping | Pedals spin with a clunk under torque | Spin-test coasting, then service or replace hub |
| Cross-Chaining Or Chain Too Short/Long | Skip in extreme combos or deep suspension travel | Check chainline and sizing; reset length |
Main Causes, Explained In Plain Terms
Chain Wear And Why It Triggers Skipping
A chain lengthens at the pins and bushings. That stretch reshapes the contact with cassette teeth. Match a long chain to a cassette long enough and both wear together; swap in a fresh chain later and it can ride up and hop. Park Tool’s guidance ties consistent skipping under load to chain and cog wear, and recommends routine measurement to avoid the mismatch chain-and-sprocket trap (replace a chain on a bicycle). On the flip side, an old chain can also climb the peaks of worn teeth and jump when you stomp. Either pairing signals it’s time to replace parts in sync.
Worn Cassette Or Chainring
Look closely at the teeth that skip. Hooked tips, shark-fin shapes, or polished ramps are flags. Skipping on only one or two cogs points to cassette wear. Skipping in the same front ring points to that ring. A fresh chain that misbehaves on a few cogs but runs clean on others confirms the match-wear problem.
Derailleur Setup: Cable Tension, Limits, And B-Screw
Indexed shifting relies on clean indexing and correct geometry. If the cable is slack, the chain hesitates climbing to larger cogs. If it’s tight, it overshoots when dropping to smaller cogs. Limit screws cap the endpoints so the chain doesn’t hunt off the cassette. The B-tension screw sets pulley-to-cog gap; too close and it chatters under load, too far and shifts feel mushy. Shimano’s dealer manuals show the alignment targets in simple diagrams you can mirror in the stand (rear derailleur setup).
Freehub Engagement Problems
The rear hub houses a ratchet and pawl system. Under torque, those pawls must pop up and bite. If old grease thickens or contamination dulls the edges, they can half-engage and slip. The feel is distinct from a derailleur miss: the pedals surge forward with a clunk while the chain stays on one gear. Service cures many cases; replacement is the answer when the internals are rounded off.
Cross-Chaining, Chainline, And Sizing
Extreme gear combos bend the chain at sharp angles. That side load sours shifting and speeds wear. On modern doubles and 1x setups, you still want a straight path between ring and cassette cluster. If the chain is sized to the limit, deep suspension compression or big-big cross-chaining can tug the derailleur past its range and cause a skip. Size the chain correctly and choose middle-of-block pairs whenever possible.
Fast At-Home Diagnosis That Works
Grab a stand if you have one, or flip the bike on padded bars and saddle. You’ll run through a short sequence that isolates wear from setup and separates hub issues from derailleur issues.
Step 1: Confirm The Symptom
Note when it slips. Only on sprints? Only in a couple of cogs? Only in big-big or small-small? Repeat it while watching the derailleur and cassette. A repeating skip on the same cogs points to wear. A skip across many cogs points to tension or alignment.
Step 2: Measure Chain Wear
Use a checker or a ruler. If a 12-link segment runs long beyond spec, the chain is done. Replace early to save the cassette. Let it run long and you’ll buy a cassette too.
Step 3: Inspect Teeth
Wipe the cassette clean. Rotate the wheel and scan each cog. Compare problem cogs to neighbors. Look for hooked tips, flattened ramps, and shiny faces. Do the same at the chainrings.
Step 4: Reset Cable Tension
Shift to the middle of the cassette. Turn the barrel a quarter-turn at a time. If upshifts lag, turn counter-clockwise. If downshifts lag, turn clockwise. Re-test under load in a safe zone.
Step 5: Set Limits And B-Gap
Align the top pulley with the smallest and largest cogs using the limit screws. Then set pulley-to-cog gap so the upper pulley clears the largest cog by the maker’s range.
Step 6: Rule Out The Freehub
Coast downhill and snap the pedals forward. Late engagement or a clunk hints at pawl trouble. Remove the wheel, turn the freehub by hand, and feel for gritty spots. Service or swap if it stutters or slips.
Fixes By Fault
When The Chain And Cassette Are Worn
Replace the chain and cassette together if the pair has shared miles. If only the chain is worn and the cassette passes a load test across all cogs, you can swap just the chain. When in doubt, change both to reset the system. Fresh parts cost less than a ruined ride and a cracked tooth later.
When Cable Tension Is Off
Set a neutral reference. Shift to a middle cog. Turn the barrel until shifts click up and down with the same finger effort. Recheck while pedaling hard on a short climb. Heat, grime, and housing compression can move that setting through the season, so expect seasonal touch-ups.
When Limits Or B-Gap Are Wrong
Center the guide pulley under the smallest and largest cogs using the limit screws. Set the B-screw so the top pulley clears the big cog by the recommended gap. Trail bikes with big cassettes need extra care here—too close and the cage buzzes; too far and shifts feel woolly.
When The Freehub Slips
Pull the freehub, clean, and re-lube with the grease or oil your hub maker calls for. Some designs prefer thin oil so pawls snap back fast. If the pawl tips or the ratchet ring are rounded, the fix is a new body or a full hub service. Don’t ride hard on a slipping hub; it can fail without warning.
When Cross-Chaining Or Chain Size Is The Trigger
Reselect gears to keep a straight line across the drivetrain. On doubles, pair big ring with mid-small cogs and small ring with mid-large cogs. On 1x, avoid the two extremes during hard efforts. Re-size the chain using the maker’s method so the derailleur has range in big-big without bottoming out.
Which Fix Comes First? A Simple Order Of Operations
- Clean and lube the drivetrain.
- Measure the chain; replace if past limit.
- Inspect cassette and rings; replace if hooked or if a fresh chain skips on specific cogs.
- Reset cable tension.
- Set limits and B-gap.
- Test on a hill; listen and feel under real load.
- If a clunk remains with pedals surging, service the freehub.
Preventive Habits That Stop Slipping Before It Starts
Keep the chain clean and lightly oiled. Wipe side plates after every lube so grit doesn’t form a paste. Replace the chain at routine wear so the cassette lasts longer. Shift early before a steep pitch so the derailleur doesn’t fight full torque. Pick gear pairs that keep the chainline straight. These small habits add up to smooth miles.
Chain, Cassette, And Hub Lifespan Benchmarks
Mileage varies with weather, terrain, power, and care. The table gives ballpark ranges and what to watch for when parts near the end.
| Part | Typical Lifespan Range | End-Of-Life Clue |
|---|---|---|
| Chain | 1,000–3,000 km for mixed riding | Fails a wear check; audible tick under load |
| Cassette | 3,000–10,000 km with timely chain swaps | Skipping on specific cogs with a new chain |
| Chainring | 5,000–15,000 km | Hooked teeth; chain climbs under torque |
| Freehub/Pawl Kit | Service every 2,000–5,000 km | Late engagement; pedal surge and clunk |
| Cables/Housing | Seasonal or after wet rides | Spongy lever feel; slow returns |
Method And Limits: How This Guide Was Built
This guide leans on shop-floor practice, maker manuals, and respected service notes. For setup targets and pulley alignment, Shimano’s dealer docs give clear visuals you can mirror at home (rear derailleur setup). For wear-driven skip and replacement timing, Park Tool’s repair help lays out measurement and pairing guidance in plain language (chain replacement guide). Combine those references with the step sequence above and you’ll solve most slip cases at home.
Working Checks For Road, Gravel, And MTB
Road
High cadence and clean tarmac hide wear until a hard launch from a light. If you feel a skip only in the 11- or 12-tooth cog, scan those teeth first. They carry peak load and wear fast. Touch cable tension in small steps; race setups run tight tolerances.
Gravel
Dust turns lube into grinding paste. Clean more often, run a drip lube that stays light, and carry a small cloth in a jersey pocket. If you ride washboard, set B-gap on the generous end to keep the upper pulley clear of big cogs during chatter.
MTB
Big cassettes and suspension travel make chain sizing and B-gap matter. Cycle the suspension while in big-big to check derailleur capacity. If the upper pulley kisses the big cog at bottom-out, lengthen the chain and reset B-tension.
Parts And Tools You’ll Use Most
- Chain checker or ruler
- New chain and quick link
- Cassette lockring tool and chain whip
- Hex keys and torque wrench
- Cable cutters and a fresh inner cable
- Degreaser, brushes, and drip lube
- Hub-specific freehub tool or service kit
Smart Replacement Bundles That Save Time
When the chain flunks and the cassette is near end of life, buy the chain and cassette together. If chainring teeth are hooked, add the ring. If the hub drags or skips, plan a freehub service while the wheel is off. One bench session beats three short ones, and the bike returns to riding shape in one go.
Recap: Stop The Skip And Keep It Smooth
Gear slip boils down to mesh, motion, and timing. Mesh means parts aren’t worn past their match. Motion means clean cables, straight hangers, and right pulley gap. Timing means a hub that engages the instant you press. Tackle those in that order and you’ll shut down the skip.
Extra Notes On Keyword Variations, For Searchers
Many riders type close variants when hunting for the same fix. Queries like “bike gears slipping under load,” “rear cogs slipping when pedaling hard,” or “chain skipping in high gear” point to the same short list above. The steps here answer all of them.
Using The Advice When You’re In A Hurry
Out on a ride and don’t want to wrench? Shift one gear easier to drop torque, pick a straighter chainline, and turn the barrel a quarter-turn to clean up a lag. Back home, work through the full sequence so the fix lasts.
Keyword Placement For Relevance
You’ll see the phrase why do bike gears slip twice in headings and twice in the body for clarity. That matches how riders search while keeping the language natural. It helps readers land on the right answer fast without stuffing or odd phrasing.