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Bike Chain Skipping – Why Chains Skip And How To Fix It

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Picture this: You’re cruising along on your trusty bike, enjoying the thrill of the ride, when suddenly, your bike chain starts misbehaving.

It skips between gears without your command, leaving you in the wrong gear or even worse, compromising your safety and confidence on the road.

We’ve all been there.

A skipping bike chain is no fun.

But fear not! In this article, we delve into the frustrating phenomenon of bike chain skipping and uncover effective strategies to put an end to it once and for all.

Reasons Why Bike Chains Skip

A skipping bike chain is distinct from a skating chain.

In the case of the latter, the chain slides across the top of the sprocket, usually because of worn sprocket teeth.

If you talk about a bike chain slipping, you may need to explain yourself further.

“Slipping” is a more ambiguous term.

There are several possible reasons for a bike chain skipping gears.

Poorly Indexed Gears (Rear)

If your gears are indexed correctly, the derailleur will move your chain flawlessly between sprockets on the rear cassette (or freewheel) every time you change gears.

On a properly indexed bike, the derailleur aligns with each sprocket as you move up and down the gears using your shifter.

A bike with poorly indexed gears makes gear changes unpredictable.

This is because the rear derailleur does not sit directly above the sprockets when you shift gears.

A skipping chain will often result.

Jumping gears are often gears that haven’t immediately switched because of poor indexing.

You can index your gears at home, preferably with the bike mounted on a bike stand, or you can ask your local bike shop to do it for you.

We’re focusing mainly on the rear derailleur here, as the front derailleur is less likely to cause skipping issues.

The remedy described below can also be applied to the front derailleur to fix problems like chain rub or a chain coming off one of the chainrings.

The right barrel adjuster for the front derailleur often sits on the down tube of the bike, which lets you make adjustments while you ride.

You can often silence a noisy drivetrain this way. Using the trim feature on many bikes should fix chain-rub issues.

How To Fix

Before indexing your gears with a derailleur adjustment, note the limiting screws, or limiter screws that are sited on the derailleur.

There are two: an outward limiting screw and an inward limiting screw.

You shouldn’t normally need to touch the limiting screws, but if you’ve had problems with your bike chain sliding off the edge of the cassette and into the spokes or frame, they’ll need adjusting ASAP.

Simply put, you adjust the H-limit screw (highest gear) so that the chain is aligned with the smallest sprocket at the rear without allowing the derailleur to travel beyond it.

You adjust the L-limit screw (lowest gear) to do the same with the largest rear sprocket.

To index the rear derailleur, you first need to locate the small dial on the derailleur known as the barrel adjuster.

The barrel adjuster alters the position of the derailleur slightly by tightening or loosening the gear cable in small increments.

First, shift your gears into the smallest ring at the front (easiest) and the smallest sprocket at the rear (hardest).

Try shifting up a gear to the next largest sprocket at the rear.

If the gear change is made silently and smoothly, the gears are likely to be already indexed.

Try all the gears to check this.

If, after shifting, you hear a lot of noise and the chain doesn’t easily move, you need to index the gears.

You index the gears by gradually turning the barrel adjuster until the chain moves across the sprockets smoothly and quietly.

Turn the adjuster counter-clockwise (matching the direction of chain travel) to adjust gear shifts from small to large sprockets or cogs.

Check all of your gears using the above indexing process.

If some gear changes are quieter and smoother than others, you may have a problem elsewhere.

Bent Or Wonky Rear Derailleur Hanger

Another way you might fix a skipping bike is to look for a bent or misaligned derailleur hanger.

This is the plate that holds the rear derailleur in place.

A bent hanger is always something to look for if you’ve either crashed your bike or it’s fallen on its drive side.

This is also one of the main reasons you should always lay your bike down onto its non-drive side (i.e., opposite side to the chain).

This problem can cause some very odd bike chain skips.

For instance, you may not be able to reach certain gears at all, so the chain will jump over one gear onto the next.

Or you might only make a specific gear if you’re shifting upward or downward.

How To Fix

First, you have to confirm that the hanger is misaligned.

You do this by simply looking at the rear derailleur and chain to see if it lines up with the cassette sprockets on the rear cassette.

It will usually be obvious if it’s wonky.

Typically, the hanger will be bent inwards towards the wheel, so you need to bend it outwards.

There is a dedicated tool for aligning a bent hanger, but it’s expensive.

Thus, you can either bite the bullet and buy one or take your bike to the local mechanic or bike builder for fixing.

You can also use an adjustable wrench to straighten a bent hanger, though this method is less accurate.

It will make your gears work again if you do the job carefully.

The jaws of the wrench should extend past the derailleur mounting hole when performing the task.

Note: Do not attempt to bend the whole derailleur into place (it must be removed before straightening the hanger).

Video: Fixing Bent Derailleur Hangers

Cable Tension & Loose Cables

On bikes with mechanical derailleur gears, efficient gear shifting depends to a large degree on shifter cable tension.

Normally, a loose cable is responsible for skipping gears, so you need to tighten it.

Note that tension in the cable is affected by various things.

On a new bike, “cable stretch” may cause the cable to become loose over the first few rides.

Opinions vary as to how much cables stretch on a bike, but they do effectively elongate as new cable housings and ferrules begin to seat.

Some cables are sold “pre-stretched”, which implies that a degree of stretching is possible in regular bike cables.

Cable tension is usually the cause of front derailleur chain skips, especially on bikes with three chainrings (the middle ring is often skipped).

How To Fix

You can add tension to gear shift cables in small increments by using the barrel adjusters mentioned above.

However, there may be times when you need to unscrew the cable anchor bolt on the derailleur if you want to add more tension.

Problems with cable tension can also be caused by dirty or kinked cables.

Dirty cable housings will also affect gear shifting because they create friction with the cable.

Replacing all your cables and housings at regular intervals helps to avoid a skipping bike chain.

Chain & Cassette Wear (& Chain Skating)

Although chain and cassette wear is often given as a cause of skipping, in truth, it is more likely to cause “skating” or “slipping”.

This is where the chain rides over the top of a cassette through sprocket wear, causing a loss in pedaling/drive power.

It’s usually a new bike chain on a badly worn cassette sprocket that causes chain skating when pedaling hard (e.g., uphill).

This is a linear problem, as opposed to the lateral problem of a skipping chain.

A worn chain does not ordinarily affect gear shifting.

A worn chain may also cause skating on a new chainring.

This scenario rarely arises, because most people install a new bike chain with a new chainring.

Video: A Chain Skating Or Slipping Over Sprocket Teeth

How To Fix

The best way to prevent the problem of skating is to monitor wear and fit a new chain before the old one becomes overly worn.

A worn-out chain wears down pricier components like the cassette and chainrings.

The opposite is not true.

You’ll usually save money by installing a new chain when necessary.

There are various ways to determine when to replace a bike chain and why your bike chain keeps falling off, and how to fix it.

How To Tell If The Chain Is Skipping

A skipping chain is a gear adjustment issue on a bike with multiple gears.

The problem will usually occur at the rear wheel, where most gear changes take place.

If the chain is going to skip gears, you’ll often hear a lot of noise while it struggles to find its place on the cassette.

Usually, this place will be the sprocket adjacent to the one it’s on.

You may experience unexpected or delayed gear changes, which can occur with a jolt if you’re climbing a hill or sprinting at the time.

Final Words

With a little care and basic bicycle maintenance, you can avoid most of the issues that cause skipping chains.

Performing your own gear indexing and replacing cables regularly will go a long way!

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Glenn Harper
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When Glenn isn't writing for BikePush, he can often be found cycling on his local rural roads. If he can help you benefit from bicycling in some small way, He’ll consider it a win.

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