Do Bike Chains Stretch?

The Short Answer is:

Bike chains do not physically stretch out and become longer, but as they wear, the distance between links increases, which is often referred to as "chain stretch". This can cause serious inefficiency in the drivetrain and even risk a chain failure. It is important to regularly check your bike's chain for wear and replace it when necessary.

Do bike chains stretch? This is a common question among cyclists, especially those who are new to the sport. The answer is yes, bike chains do stretch over time. However, the term “stretch” can be a bit misleading. The side plates of an old chain are not actually pulled out of shape by the repeated stresses of pedaling.

Rather, the pins and bushings wear down, causing the chain to elongate. This elongation can cause the chain to no longer line up perfectly with the teeth of the cassette, leading to poor shifting and premature wear of the cassette and chainrings.

In this article, we will explore the causes of chain elongation, how to measure chain wear, and when to replace your bike chain. We will also discuss the pros and cons of belt drives versus chain drives, as well as the controversy surrounding chain maintenance.

Understanding Bike Chain Stretch

Bike chain stretch is a common term used to describe chain wear, which is the most important type of chain wear. The pitch of the chain grows in length as it wears, and this growth comes from the bushings worn with the chain pins.

The inner diameter of these bushings increases, and the pins groove out. The holes in the inner and outer link plates, through which the pin sits, also enlarge over time. This elongation effectively lengthens the pitch of the chain, and it is this elongation that is commonly referred to as chain stretch.

Chain wear manifests as ‘stretching’, and this is when the chain link touchpoints between its pins and bushings wear away. Due to chain wear, less material means the chain ‘stretches’ in length. And that’s horrible for your drivetrain’s responsiveness because it will start to skip on shifter inputs.

Chances are that you will see signs of chain stretch long before a chain breaks. In fact, breakage is very rare with modern chains. More common is one or more of the following symptoms: excessive rattling, grinding, or other unusual noises coming from the chain drive, wear on the teeth of sprockets, often in a ‘shark tooth’ pattern, and poor shifting performance.

It is important to note that the chain isn’t actually stretching at all; it is the pins holding the links together that wear and elongate, effectively lengthening the pitch of the chain. The holes in the inner and outer link plates, through which this pin sits, also enlarge over time.

To prevent chain stretch, it is important to keep the chain properly lubricated. A chain typically is moved by a sprocket, and both chain and sprocket are prone to rapid wear unless properly lubricated. Regular cleaning and lubrication of the chain can help prevent chain stretch.

In conclusion, understanding bike chain stretch is important for maintaining the longevity of your bike’s chain and drivetrain. Regular cleaning and lubrication of the chain can help prevent chain stretch, and it is important to replace the chain when it reaches one percent growth from the original 0.5in (12.7mm) pitch.

Causes of Chain Stretch

Bike chain stretch is a common problem that can cause issues with gear shifting and lead to costly repairs. Here are some of the causes of bike chain stretch:

1. Wear and Tear: Chain wear is commonly referred to as ‘chain stretch’ because the chain’s pitch grows in length as it wears. This is the most important type of chain wear, and the growth comes from the bushings worn with the chain pins. Over time, the inner diameter of these bushings increases and the pins groove out. A new chain at a 0.5 pitch is designed to sit deep into the cog. As the pitch increases, the chain rolls higher up on the tooth and causes rapidly increased cog wear as the point of contact is reduced. Too much wear and the chain will start skipping over the top of the cog.
2. Lack of Lubrication: The most important factor in preventing chain stretch is lubrication. If roller chains are poorly lubricated, stretching will take place very quickly.
3. Misalignment: Misalignment of the chain can cause it to wear unevenly and lead to chain stretch.
4. Overloading: Riding puts your average chain under all sorts of high loads, particularly mountain biking where the chain may snap and twist around through all sorts of conditions. This type of wear could lead to the chain weakening and potentially snapping under power.
5. Poor Maintenance: A poorly maintained chain can lead to chain stretch. Regular cleaning and lubrication can help prevent chain stretch.

It’s important to check your bike chain regularly for signs of wear and stretch. If you notice any issues, it’s best to replace the chain before it causes further damage to your bike. The average amount a chain can stretch before it is considered too stretched and needs replacing is when it has increased in length by 1%.

Signs of a Stretched Bike Chain

A stretched bike chain can cause serious inefficiency in the drivetrain and even risk chain failure. Here are some signs to look out for:

1. Jumping gears: One of the first signs of chain wear and stretch is jumping gears. The chain links are no longer aligning with the cassette cogs and the chain just never seems to settle in and behave. If gear adjustment fails to fix this, check your chain wear.
2. Smoother running: If your chain is running smoother than usual, it may be a sign that it has stretched.
3. Chain checker: Use a chain measuring tool or a standard metal ruler to check chain stretch and wear. If the chain is worn, the two ends of the tool will fall into the chain links and it will sit flush with the chain. If the chain is okay, the tool will sit above the chain. Chains don’t wear evenly, so for the most accurate result, it’s best to take measurements on at least three different parts of the chain.
4. Slipping chain: If you notice your chain slipping out of gear or catching and sliding when in gear, it may be a sign that your chain is stretched.

If you notice any of these signs, it’s time to replace your bike chain. Remember, chain wear is the result of a blend of mileage, conditions, and maintenance. So, it’s important to regularly check and replace your bike chain to ensure a smooth and efficient ride.

Consequences of Riding with a Stretched Chain

Riding with a stretched chain can have several consequences that can affect the performance of your bike and even lead to accidents. Here are some of the consequences of riding with a stretched chain:

• Increased wear on the cassette and chainring: A stretched chain can cause more wear on the cassette and chainring, which can lead to the need for costly repairs.
• Shifting difficulty: A stretched chain can cause difficulty in shifting gears, which can affect the overall performance of your bike.
• Chain jumping: A stretched chain can cause the chain to jump gears, which can be dangerous, especially when putting power down or climbing.
• Chain lash: A loose chain can cause chain lash, which means that it’s slapping and causing a lot of noise, especially when you start to accelerate or decelerate. This can cause a jerky feeling at virtually every acceleration. If a motorcycle chain is loose, there’s a higher chance that the chain will break. If there’s too much slack in the chain, during an aggressive acceleration the front sprocket can strongly jerk the chain. If the chain is worn out, this force can break its weakest link. In most cases, the broken chain simply drops to the ground and you lose power. However, the chain can also wrap around the rear sprocket causing a jam.
• Reduced suspension travel: A loose chain can reduce suspension travel due to the high amount of tension.
• Power loss: A tight chain can cause power loss due to higher friction, while a loose chain can cause power loss due to the chain slipping.

To avoid these consequences, it’s important to check and replace your chain regularly. One of the first signs of chain wear and stretch is jumping gears. If gear adjustment fails to fix this, check your chain wear.

On a used chain, there will be some stretch. If this is less than 1/16″ (1.6mm), the chain is still fine to use, but keep checking frequently. If the chain growth is greater than this, it’s time to replace the chain.

Measuring Chain Wear and Stretch

Bike chain wear is a common issue that can lead to poor shifting and even damage to your bike’s drivetrain. Here are some methods to measure bike chain wear and stretch:

1. Using a Chain Checker Tool: The easiest and most accurate way to determine chain wear is by using a tool such as the CC-3.2 Chain Checker or the CC-2 Chain Checker. These tools are specifically designed to measure chain wear and will give you an accurate reading of how much your chain has stretched.
2. Using a Ruler: Another ballpark method for checking chain wear is by measuring it with a ruler. Pick a rivet and line it up at the zero mark. Count 24 more rivets and your last rivet should be at the 12″ mark of your ruler. If it is off by more than 1/16″ your chain is stretched to the point of replacement.
3. Using a Tape Measure: Using a ruler, a new chain should measure exactly 12 inches across 12 links, from the middle of a pin to the middle of the pin. The number most commonly agreed on for a worn chain is one percent elongation between links. In reality, though, you should replace the chain before this point.
4. Breaking the Chain: Break the master link and stretch your chain out on a workbench in a straight line. Now count out 100 spaces and mark the first and last pins. If the straight end does not fit down between the rollers and gets stuck on one, it has worn or “stretched” to its wear limit.
5. Using a Chain Wear Tool: You can also use a chain wear tool to measure chain wear. These tools are designed to show you different levels of chain wear, showing if the chain has stretched by 0.5 percent, for instance. Many will be double-sided.

It’s important to note that a worn chain can cause damage to other parts of your bike’s drivetrain, so it’s important to replace your chain before it becomes too worn. A good rule of thumb is to replace your chain every 1,000 to 2,000 miles.

Preventing Chain Stretch

Bike chain stretch is a common problem that can cause shifting issues and reduce the lifespan of your bike’s drivetrain. Here are some tips to prevent bike chain stretch:

1. Lubrication: The most important factor in preventing chain stretch is lubrication. Poorly lubricated chains will stretch quickly. Make sure to lubricate your chain regularly with a high-quality lubricant.
2. Cleaning: Keeping your chain clean is also important. Dirt and grime can cause wear and tear on your chain, leading to stretching. Clean your chain regularly with a degreaser and a brush.
3. Replacement: Once a chain has elongated 3% of its original length, it must be replaced. Replacement is expensive, time-consuming, and necessarily involves production shutdowns, so a business wants to get as much life out of its chains as possible.
4. Check for wear: Use a chain checker tool to check for chain wear. A worn chain can wear the cassette and ultimately any chainrings on your crankset. Cassettes and chainrings are typically more expensive than chains, so costs can escalate.
5. Proper shifting: Avoid shifting under heavy loads, as this can cause extra stress on your chain and lead to stretching.
6. Proper storage: Store your bike in a dry place to avoid rust and corrosion on your chain.

By following these tips, you can prevent bike chain stretch and extend the life of your bike’s drivetrain.

Replacing a Stretched Chain

Replacing a stretched bike chain is an essential maintenance task for any cyclist. The chain stretches over time, and if left unchecked, it can cause damage to other drivetrain parts like the cassette and chainrings. Here are the steps to replace a bike chain:

1. Check the chain for wear using a chain checker tool or an accurate ruler. A new chain should measure exactly 12 inches across 12 links, from the middle of the pin to the middle of the pin. The most commonly agreed-on number for a worn chain is one percent elongation between links. If the chain is worn beyond this point, it’s time to replace it.
2. Remove the old chain using a quick link removal plier if your chain uses a quick link. Discard the old chain in a metal bin or recycle it at your local workshop.
3. Cut the new chain to size to suit your bike and drivetrain combination. Some users like to use the old chain as a reference point to cut the new chain to length.
4. Install the new chain by threading it through the derailleur and cassette, making sure to route it correctly. Use a chain tool to connect the ends of the chain.
5. Finally, check the chain for proper tension and shifting. If the chain is too loose or tight, adjust the derailleur accordingly.

Remember to stay on top of maintenance to slow down drivetrain wear, such as cleaning your chain regularly and checking it for wear using a chain-checker. By replacing your bike chain when necessary, you can extend the life of your drivetrain and enjoy a smoother, more efficient ride.

Conclusion: Do Bike Chains Stretch?

In conclusion, while many cyclists refer to chain wear as “chain stretch,” it is actually the pins holding the links together that wear and elongate over time. As a result, the chain’s pitch grows in length, causing it to no longer align correctly with the rear cassette and chainring’s teeth.

Most experts recommend replacing a chain once it has stretched to 0.75 percent or one percent growth from the original 0.5in (12.7mm) pitch. Different tools are available to measure chain wear, but they may show different levels of wear.

Ultimately, proper chain maintenance, including regular cleaning and lubrication, can help prolong the life of a chain and prevent excessive wear.