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Bicycle chains certainly do stretch!
The more you ride, the more your bike chain will stretch. Chains stretch for a variety of reasons, including excess dirt and grime, and normal wear and tear. It is important to take measurements of your chain regularly, to keep on top of its maintenance.
The cassette will be worn out much more quickly by a chain that has been stretched.
Changing a cassette is more expensive than changing a chain; therefore, if you notice a problem with the chain, it’s best to change it sooner rather than later.
In this post, I’ll take a look at:
- What exactly a ‘chain stretch’ is
- How chain stretching works
- 3 signs of a stretched chain
- 3 causes of chains stretching
- 3 ways to determine your chain’s length
- When you should change your bike chain
- Why you should lubricate your bike chain
What is a Chain Stretch?
While it is true that chains do extend over time due to use, the term “chain stretch” can be a little confusing.
Since it is not true that the chain links themselves are getting longer, the phenomenon is better referred to as chain elongation rather than chain stretch.
Let’s think about roller chains for a moment (you know, the type of standard rolling chain you find on bicycles). In the context of roller chains, the term ‘chain stretch’ refers to the bending of any one or more of the individual links.
The vast majority of chains used in modern bicycles are roller chains. They consist of multiple parts, specifically:
- Inner/Outer plate
The pins of a chain are the weakest links and often break first. To be more specific, the pins are not growing in length but rather experiencing one of several conceivable impacts.
Some top facts about the chain links include:
- They can be twisted, but only so far.
- Their diameter may shift if they shed mass due to friction.
- It’s possible that the pin insertion holes in the plates will be enlarged slightly.
- Parts of a roller chain are susceptible to wear and failure from repeated exposure to the destructive forces of friction, weight, and heat.
Single (simplex), double (duplex), and triple (triplex) roller chains are all distinct varieties. The greater the weight being carried, the more strands will be present in the chain.
Warning – If you don’t regularly oil your chain and sprocket, they’ll wear down quickly.
Chain Stretching Explained
Here is how the whole thing works broken down…
A chain consists of pins that hold inner and outer plates together. These sandwich a roller in the center.
When observing the chain from the side, the plates will appear as flat objects with a number 8 pattern; the pins will sit in one of the number 8’s holes, and the rollers will be kept in place by the pin and plates.
Two opposing forces are acting on the plates when you pedal: the forward mechanical thrust of your legs and the resistance of the road, the gears, the wheel, friction, gravity, etc.
The plates don’t change shape, but the pins at the junctions between them do, becoming squeezed on both sides.
The joints are subjected to stress every time the chain goes around a sprocket, in addition to the compression from the plates.
The plates sever the pin near its joining surface. One may compare this to a knife being held against a spinning apple on a stick, gradually cutting deeper into the fruit as it spun.
Each time you turn the cranks, a tiny amount of metal gets shaved off at each joint in the chain due to the cutting and squeezing of the pins, but it takes thousands of cycles for this progressive wear to become visible.
In this stage, the plates have worn grooves into the joints, reducing the mobility of the joint and increasing the length of the chain.
Recognizing the 3 Signs of a Stretched Chain
The chain’s stretch is not always visible. It takes a variety of high-quality, specialized tools from a variety of suppliers to detect chain stretch.
The tool is called a chain wear measuring tool. There are also some other measuring devices you can get, although these are not as accurate.
The two ends of this instrument are toothed. When the teeth fit through the chain’s openings, it indicates the chain has been stretched and has to be replaced.
There is a risk of the chain breaking, which could cause gears to be damaged if they are not replaced.
Here are some tell-tale signs to look out for:
1. Skipping Links in a Chain Reveals a Torn or Stretched Link
It’s possible that if the chain is excessively long, it will fall off the gear briefly as you pedal more forcefully. It’s as if the pedal suddenly stopped working or the wheel suddenly slipped.
If this is happening, it’s probably because you have a stretched chain.
2. Rear-Gear Wear and Tear
Riding with an extended chain causes the back sprockets to wear out faster, which can lead to chain skipping even with a brand-new chain.
It is not easy to tell how much wear there is on the rear gear just by looking. It is more something you will ‘experience’ through chain skipping.
3. Front Sprockets Show Signs of Wear
The front sprockets will wear out if you cycle for a long time with an extremely long chain.
While sprockets reduce the frequency of chain skips, the worn teeth become beveled, causing the chain to either fly off the sprockets with a bang or get caught and pulled apart at the bottom.
3 Causes of Chain Stretching on Bicycles
There are primarily three causes for chain stretching on bicycles.
1. New Chain for Your Bike
New bike chains tend to stretch because the metal links are stiff and cold.
This is the primary and most prevalent reason why bike chains lengthen. The metal links in a chain will warm up and expand with use.
2. Dirt and Dryness
Aside from use, wear is also a cause of chain stretch on bicycles.
Wear can be accelerated by both grime and a lack of lubrication. In ideal conditions, a well-maintained and oiled chain may carry a heavy weight for more than 20,000 miles before showing any signs of wear.
3. Punctured Chain Links
Pins in a chain are impervious to damage, although they are easily deformed. As a result of frictional material loss, they can twist slightly or experience slight variations in diameter.
When using pins, the holes on the plates may get slightly larger. (Source)
How Do I Determine The Chain’s Elongated Length? 3 Ways
Often the only way to know if your chain has stretched is the old-fashioned one – to measure it!
The elongation of chains can be evaluated in three different ways:
1. Use a Ruler
Not rocket science this one! But this is probably the best method.
Once the ruler is correctly aligned on the straightened chain, you can take an accurate measurement.
The measurements are in inches, not centimeters.
As I previously mentioned, the length of a single link in a chain is exactly 1 inch.
Determine the size of the chain by counting and measuring 12 links. The elongation of the chain is approximately 0.5% if its 12 links are longer than 12 inches by 1/16 of an inch. A 1% chain elongation is present if the chain measures more than 12 inches by 1/8 of an inch.
Here is a table that gives you an indication of just how stretched your chain is:
|Length over 12 inches||Percentage Stretch||Action|
|1/32 of an inch||0.25%||The chain should continue to work well|
|1/16 of an inch||0.5%||Consider changing for optimum performance|
|1/8 of an inch||1%||Change the chain to prevent damage to other parts of the bike|
|1/4 of an inch||2%||Change chain to prevent damage and for safety|
How stretched can a bike chain be? In reality, the maximum amount a chain can stretch is about 1% of its length. Realistically, any chain about 0.5% of its length would need to be replaced for optimum performance.
If you prefer to convert to centimeters, things look a little different. Ten links of the chain are measured.
Given that the zero on the ruler coincides with the center of one pin, we check the location of the pin on the tenth link to see if it is in the correct position. No stretching has occurred if the measured value is exactly 25.4 centimeters.
The chain elongation is 0.5% when aligned to 25.53 cm.
This chain elongation is 1% when aligned with 25.65 cm.
2. Detach the Chain at the Front Sprocket
Pulling the chain forward on the front sprocket is one way to free it from the sprocket. A broken chain is indicated if the entire top of a tooth can be seen when the chain is lifted.
Although this approach lacks precision, it is useful for a speedy assessment!
3. Use a Specialized Instrument for Measuring the Length
This device hangs from the chain by just resting on top.
Warning number 1 – The tool has to be replaced if the teeth on the ends of it are damaging the chain.
Warning number 2 – One potential downside of this strategy is the occurrence of a false alarm. Extensive wear on the rollers is often indicated by a run-in in the chain.
When the tool is dropped into the chain, the elongation may not be 0.5% yet because just the pins’ wear impacts the elongation. Softer roller chains are more prone to this problem. (Source)
So Why Is It So Important To Consider Chain Stretch?
The constant stress on the joints will ultimately lead it to break, and then it may become stuck in the hub and cassette, or in the spokes of your back wheel, around your leg, or in the wheel of the guy behind you!
However, if the chain is too long, it won’t fit properly in the sprocket and will shift poorly or possibly skip.
It is advisable to replace the chain and sprocket simultaneously to avoid having to repair or replace the cassette prematurely due to a worn chain.
When Should I Change My Bike Chain?
Each link in the new chain measures 1 inch in length.
A fresh chain can be used when the old one has grown in length by roughly 0.5%. This is to optimize the performance of the bike.
However, the front and rear sprockets will continue to function normally if you don’t change the chain soon. By extending their time in this manner, their usefulness will increase.
Rear sprockets can be used with two to four chains before they wear out and need to be replaced, provided the chains are changed regularly.
When the rear sprockets wear out to the point where they interfere with the chain’s motion, it’s time to replace the chain.
It is crucial to remember that chain wear does not occur linearly to monitor, so you need to keep monitoring it effectively.
This is because the numerous surface hardening treatments and low friction coatings found on most grade chains will gradually wear away with use, hastening the deterioration of the underlying materials.
More contamination will build up inside the links of the chain as time goes on.
You should certainly change the chain that has stretched to 1% longer, as this could issues for several other parts of your bike.
If you’re not sure what length of chain to get as a replacement, then follow the strategy in this video:
Why is it Important to Lubricate the Bike Chain?
Some cyclists may neglect their chains in favor of more visible parts of their bikes, such as their brakes or tires.
But keep in mind that your bike can’t go anywhere without its chain, and if you don’t take good care of it, it will break and cause further problems for your bicycle.
Maintaining your bike’s chain with grease will keep it riding smoothly throughout the year. I’ve outlined the primary advantages of chain lube and why you should be using it frequently here:
- Increase the lifespan of your chain by preventing the wear and tear that comes from metal-on-metal action.
- Save cash by avoiding frequent chain replacement by maintaining it properly.
- Your chain will not rust or corrode due to the elements, as they cannot get through the protective barrier provided by the lubricant.
- You can lessen the amount of noise your chain makes by lubricating and adjusting it properly if you’ve noticed it getting noisier. Clean, well-oiled chains with the right amount of strain are noticeably less noisy.
- Improved shifting—a dry chain might hinder your bike’s performance by reducing the effectiveness of the gear shifts.
How Frequently Should you Swap Out your Bike’s Cassette and Chain?
If you bike frequently, you should take care to maintain these parts.
Replace your bike chain every 1,500 miles or so as a general rule.
You may need to replace it more often if you bike in muddy or sloppy conditions. When the old chain starts to skip or feels loose, you know it’s time to replace it.
Unlike chains, cassettes don’t break as frequently and can last longer between replacements. You may not have to replace your cassette for another two to three years of riding, depending on how often you ride and where you travel.
But if you hear a slipping or grinding noise from your gears, it’s usually time to get a new one.
Here’s a great video that demonstrates exactly when you should be looking to change your bike chain:
Everyone has an opinion on chain wear, just like they do on which tires to buy or which chamois cream is best.
It’s easy to get caught up in the minute specifics of when a chain is worn and what function each chain checker serves.
The bottom line is that it’s cheaper, in the long run, to replace a stretched chain than to risk more damage to your bike!