What skipping looks and sounds like
Gear problems usually show up in a few ways. The chain may jump suddenly over the teeth when you pedal hard, which feels like a lurch or a sudden loss of resistance. The gears may refuse to settle into one position and rattle or hesitate. Or the chain may rub against a neighbouring gear and make a continuous scraping or clicking noise.
A skipping chain under load is more than annoying. A sudden slip can throw your foot off the pedal or make you lose balance, so treat it seriously, especially when climbing or sprinting. This article is general information. Bikes, components and gear systems differ, so follow the maker’s instructions and see a bike shop if you are not comfortable with an adjustment.
A quick note on how gears work
On a bike with a derailleur, a cable pulls the derailleur to move the chain from one gear to the next. The system relies on exact positioning: the derailleur must line up with each gear, and the chain, cassette and chainrings must fit each other well. A small change in any of these can upset shifting. If you want to understand the mechanics, the basics of how bike gears work are worth a read, and good shifting technique helps too.
Common causes, from simple to serious
A dirty or dry drivetrain
Grit and old lubricant on the chain and gears make shifting sticky and noisy. Clean and lubricate the chain, following the lube maker’s directions, and wipe off the excess. This is the simplest check and often improves matters.
Cable tension and adjustment
Over time, gear cables can stretch slightly and settle, and housings can get dirty or dry. The result is that shifting becomes slow, the chain will not reach the next gear, or it rubs in between. Many derailleurs have a small barrel adjuster where the cable enters, which allows small tension changes. Turning it by tiny amounts can improve the shifting, and many riders learn to do this. Make small changes, test after each, and follow the instructions for your system. If one adjustment does not help, stop and ask a shop.
A worn chain or cassette
If the chain has stretched, it no longer fits the gear teeth properly and can jump under load. If the gears themselves are worn, a new chain may skip too. A skipping chain that is clean and well lubricated is a classic sign of wear. Shops check this with a dedicated tool, so if you suspect it, have the chain measured rather than guessing. Chain wear is often the reason a drivetrain that once worked well now skips only in the gears you use most.
A stiff or damaged link
A single stiff link makes the chain jump each time it passes over the gears or derailleur. You may see it as a regular skip or hear a click once per rotation. Sometimes a little lubricant and flexing frees a stiff link, but a bent or damaged link usually needs a new chain section or a new chain.
Bent or damaged derailleur hanger or derailleur
The derailleur attaches to the frame through a small replaceable part called the hanger. If the bike has fallen on the drive side or been knocked, the hanger or derailleur can bend slightly, which moves the derailleur out of line. The symptoms are shifting that cannot be tuned out, a chain that rubs or jumps in particular gears and a derailleur that looks crooked from behind. Checking and correcting alignment needs a special tool and experience, so this is a shop job. A post-crash bike check should include it.
Worn or sticky cables and housings
Rusty cables, frayed ends or cracked housings add friction. If shifting feels heavy or the lever returns slowly, it may be the cable. Replacing cables and housings is a standard shop service.
A bent or worn chainring or cassette
Bent teeth, a warped chainring or worn sprockets can cause skipping or rubbing. Visual damage, hooked or pointed teeth and wobble in the chainring are all signs for a mechanic to inspect.
Wheel not seated properly
If the rear wheel is not fully in the dropouts, the gears sit out of line. Check that the wheel is fitted correctly, and do a wheel retention check if you are not sure. This is a simple but important thing to rule out, especially after fixing a flat.
Cross-chaining and riding habits
Running the chain at a steep angle, for example from the largest chainring to the largest rear sprocket, often causes noise and extra wear. Avoiding that kind of cross-chaining, and moving through gears before a climb rather than under heavy load, helps the drivetrain last. Among common gear shifting mistakes are changing gear while pedalling very hard.
Differences between systems
Not every bike uses a derailleur. Hub gears, belt drives and single-speed bikes have different fault patterns, and some derailleurs have clutch mechanisms that affect chain tension. If you have an unusual setup, consult the maker’s instructions.
A simple order of checks
- Look and listen. Which gears skip? Only the small ones, only under load, or all of them?
- Check the basics. Is the wheel fitted properly, and is the chain clean, lubricated and free of stiff links? A chain and gear check is a good routine.
- Look at the hanger and derailleur. Look from behind to see whether the derailleur seems to sit straight. Do not bend it back yourself.
- Try a very small barrel adjuster tweak, if you are comfortable, and test the result.
- Think about wear. If the bike is older, well used or has done a lot of miles, ask a shop to measure the chain and check the cassette.
If any step reveals damage, or the problem persists, stop troubleshooting and see a mechanic. Continuing to ride with a chain that jumps under load can be unsafe.
What to expect from a shop
A mechanic will usually check the chain wear, inspect the cassette and chainrings, align the derailleur hanger if needed, replace cables if they are the cause and fine-tune the shifting. Describe when the problem started, whether it follows a crash or a wash, and which gears are affected. Good information makes it easier to fix quickly.
Gears that shift well are a pleasure to ride, and most problems turn out to be simple. Because the cost of ignoring wear grows over time, early attention is usually the cheaper route.