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When should the bike chain be replaced?

A few weeks ago we explained how to change the handlebar tape on a road or gravel bike. Well, today we’re going to follow up with another basic maintenance issue that any cyclist, beginner or experienced, should be familiar with: How to tell if the chain is worn and needs to be replaced. Perhaps you haven’t thought about it even once since you bought your bike, but that set of links that resist the power of your pedaling not only requires cleaning and lubrication to function properly, but even with the best and most innovative wax dipping technique, the chain doesn’t last forever. It has a lifespan where it performs at its best but after that, it starts to slow you down and wears out the other drivetrain components it comes in contact with such as cassette, chainrings and rear derailleur pulleys.

How long does a bike chain normally last?

As per usual, our answer is: it depends. The average life of a chain depends not only on the chain itself, but also on the conditions of use as well as on the frequency and quality of maintenance. Although many manufacturers estimate a value of around 3 000 km, deterioration can happen much earlier if the chain is exposed to humid conditions and/or a lot of dirt (dust, mud…) as well as if you subject it to a lot of stress. For example, if you pedal at a low cadence and exert a lot of force, or if you use a gear ratio that stretches the chain too much. Of course, the lack of basic maintenance (cleaning and lubrication) considerably reduces the lifespan of your chain. 

In the end, all of the above increases friction and, therefore, increases the wear of the chain. If you think about it, every time you pedal, the chain moves by bending over the cogs, chainrings and derailleur pulleys. This constant friction between links and teeth leads to wear. As the chain wears, the links are stretched, which affects the distance between the chain pins and ultimately the alignment of the cog and chainring teeth. This also leads to increased wear of the cogs and chainrings. 

Why does a worn chain need to be replaced?

Mainly to avoid damaging the rest of the drivetrain. This is crucial because once the worn chain has damaged the teeth of the cassette cogs and chainrings, you will most likely have to change at least the cassette, since a new chain would just skip or slide between the worn teeth and would not allow you to pedal safely and comfortably.

Safety is another reason. A worn chain increases the risk of breakage, which can lead to a fall and/or serious injury. 

Performance is yet another reason to replace the chain. A worn chain can affect not only the smoothness of the shifting, but also the performance. In other words, it can slow you down and make you less efficient. 

The last thing is money: Although it may seem expensive to replace the chain preventively, you can actually save money in the long run by avoiding excessive wear of the cassette and chainrings. On low-end or mid-range components, you may not notice it as much, but on high-end cogs and chainrings, that can be very costly.

How do I know if the chain is worn?

Let’s get down to what we’re really concerned about. As we have said, we don’t know exactly how long a chain lasts, but we do know what causes and/or increases its wear. There are different methods of checking it, from a simple visual and manual inspection, to a digital measurement with a specific tool, to experiencing problems with the entire drivetrain. Let’s take a look at them:

Problems with the drivetrain: If you experience problems shifting gears smoothly and accurately, especially if you notice the chain skipping or slipping on the cogs, it might be a sign that the chain is worn and needs to be replaced.

Visual and/or manual inspection: If you notice that the chain links are worn, frayed or deformed, it is a sign that the chain needs to be replaced. Surely the chain doesn’t have to reach the condition in the video below for you to realize that it needs to be replaced:

You can also shift to the smallest cog in the rear and the large chainring in the front and try to lift and stretch the chain by hand as in the following video:

You can also use a simple ruler to check the wear of a chain. However, keep in mind that it is a very basic and inaccurate way to check the wear of a chain.

Vernier caliper or King Foot: With a high-precision caliper (digital or analog) you can measure different points of the chain as shown in the picture by Campagnolo. If even one of the measurements is greater than 132.60 mm, it is time to change the chain. 


Chain wear gauge: There are a multitude of models on the market with prices to suit all budgets. Some are more accurate than others, but Adam Kerin from Zero Friction – a real expert on chains – recommends the Shimano chain wear indicator and tells you how to use it:

In this PDF from his website, you can find some of his other recommendations for tools and methods for measuring the chain. Remember to shift to large cog and large chainring and, as Adam Kerin says in the video, keep in mind that wear is not linear. Therefore, the more time or use the chain has, the more regularly the measurement should be taken. Much more so if the chain is exposed to moisture and dirt. 

Finally, remember to check the wear of your chain regularly. It doesn’t matter if you’re using a ruler, a caliper, a simple wear indicator from Decathlon or if you’ve gone all out and got the fancy digital KMC chain checker. If you don’t use it often enough, it makes no sense. The best time to measure your chain is after you have cleaned it and before you put lubricant on it. 

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