How to check for chain wear

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One of the most common drivetrain problems is ‘chain skip’. This is when your chain slips forward while pedaling under pressure. There could be a few problems that are causing this. Sometimes a stiff chainlink is to blame, other times it’s a worn freehub body. However, one of the more common causes is a worn chain.

Over time, the pins and rollers that help hold together the individual links of a chain will wear and as a result the pitch (length) of each link will grow. This is why, despite the metal itself not stretching, such chain wear is commonly called chain ‘stretch’.

The standard pitch of a new chain link sits at half an inch, pin-to-pin. An inner plus an outer (wide and narrow) link of a chain makes an even inch. Chainring and cassette cogs are designed with this pitch in mind, such that the chain rides at the base of the cog/ring when new. As the chain pitch grows, it rolls higher and higher on the tooth, accelerating cog wear until eventually it just skips over the edge.

Once the chain wears, the cassette and chainrings start to wear along with it and become ‘hooked’ from the high-riding chain. It’s commonly argued that if you replace your chain before it starts to wear too badly it will dramatically increase the life of the rest of your drivetrain (cassette and chainrings). A $50 new chain every few months could save you hundreds by preserving your drivetrain.

Even when cost isn’t a factor, the likes of the top WorldTour teams regularly replace chains approximately every 1,000km (a week in a Grand Tour). Some mechanics claim they get up to three full seasons out of cassettes and chainrings this way, but more importantly, there’s far less risk of a broken chain in the heat of the moment. Additionally, a worn chain will exhibit greater twist that leads to slower and sloppier shifting.

There’s also an old mechanic saying: There’s no such thing as a broken chain – only a incorrectly installed chain!

This argument for regular chain replacement is rather clear-cut if you’re riding on Dura-Ace or Super Record components, but the value proposition becomes a tougher debate if you ride on 105 or below where replacement chainrings and cassettes are far more affordable. Additionally, you’ll need to consider the installation cost of a new chain if you’re not confident in doing it yourself. Nevertheless, if you value crisp shifting or swap between wheelsets then regularly replacing chains before significant wear is a smart choice regardless of what your components cost.

Measuring chain wear the free and easy way

So how about measuring that chain wear? Well, the easiest (and cheapest) way is as follows:

1. Shift gears so that your chain is in the big ring and smallest gear on the cassette (e.g. 53-11T)

2. Pull at the chain at the front of the chainring as shown to the right. If the chain starts to lift off the top and/or the bottom of where it sits on the chainring teeth, this means that the chain is starting to wear or is worn. This ‘lift’ is possible because the stretched chain no longer sits properly in the teeth anymore. The photo to the right shows a brand new chain; see the feature image above for a worn chain. Chances are if your chain lifts off more than our worn example, you’ll be needing more than a new chain.

The chain in this photo doesn’t lift from the chainring and so is not worn. Compare to the worn chain in lead photo.

Measuring the Chain precisely

Once you’ve determined that your chain is worn, it’s time to check to see how worn it is. If it starts to ‘lift’ on the chainring as described above, you’ll probably need to change it.

A more accurate way to measure your chain is to do the following: with your chain still on the bike, place a ruler’s zero inch mark directly above the center of one of your chain pins. Now count 12 complete links. A complete link equals one inner and one outer. A rivet on a new chain should line up exactly to 12 inches on the ruler.

A ruler is effective, but it can be fiddly to line up perfectly.

As a general rule, if the rivet is less than 1/16″ past the mark, your chain is ok. If it’s between 1/16″ and 1/8″ past the mark you’ll likely need a new chain, but your sprockets should be ok. If it’s more than 1/8″ past the mark, you’ll probably have to replace both the chain and cassette.

There are purpose-built chain-checkers that make this job even easier. The simple fixed length, drop-in style is all you need and will quickly give you a go or no-go gauge on your chain wear. Many argue the ruler method is more accurate as it’s not affected by roller tolerances, but it can be a fiddle to precisely line it up and so the chain wear gauges do exactly what they need to.

Using the popular Park Tool CC3.2 chain wear checker as an example, the .5 marking is there to give warning of needing a new chain, and the .75 is there to show a new chain is needed. For our own bikes running the good stuff, we’ll replace a chain at the .5 marking to near guarantee against any early wear.

This is the same chain as pictured in the lead photo. The tool agrees it’s worn.

This is the same chain as pictured above where it doesn’t lift from the chainring. The chain checker agrees that it’s not worn.

Worn Chainrings and cassette

This big chainring is only just starting to show signs of hooking, but it’s clear the gaps between the teeth are larger than a new chainring.

While a chain showing obvious wear is likely to need a new cassette if replaced, your front chainrings generally won’t need replacing very often. If worn they are very easy to spot, as they’ll start looking thin and like shark teeth. There are, however, no perfect tools or gauges for determining cog and chainring wear, though fitting a new chain is the surest way to reveal significant wear, since it will skip and rumble on the worn teeth.

  • Chris ONeill

    I have the park tool tool. I’ve often wondered whether to check the chain under a little tension or not as it does seem to make a difference

    • Yes, tension is important. It’s always best to measure any part of the chain that is above the chainstay rather than below it.

      • Superpilot

        Yes tension. The park tool will also have you change a bit earlier than the 1/16th & 1/8th inch rule, but it won’t hurt changing it early. Running a compact FSA Gossamer, I get about 10,000 out of the big ring because even avoiding cross chaining to big big by at least one cog, it thins the tooth width quite a bit on the chainring. The shifting starts to suffer and I know its time for another. Do a chain about every 5000. Winter really hammers them with the grit though.

        • winkybiker

          10,000km from a big chainring is pretty dire. I’m getting at least twice that, generally. Or are you talking miles?

          • Superpilot

            Nah man, kms. I know it’s dire. I changed the way I ride the gears after the first one to minimise cross chaining, not too much diff. The chain shaves the teeth thinner, so they shark tooth more easily, then shifting suffers. I busted a front derailleur when the chain was skipping and jamming on the first one. It’s a cheap groupset on my one main bike, so what can you do about it really.

            • winkybiker

              The metallurgy of the FSA rings might be a bit dodgy. FSA are CNC machined, rather forged like Shimano and Campag perhaps?

              • GoRixter

                Praxis Works, Shimano, and Campy are the only forged rings, I believe. Much higher quality. Chains make a difference too. The Campy, KMC & Shimano (by KMC) are also more precise and wear better

            • jules

              either you’re leaving the chain swap for too long, the cheap groupset is made from soft steel/aluminium, or the weather is taking a heavy toll. I like to clean my drivetrain regularly. by regularly, I mean when I get a chance. by when I … etc

        • winkybiker

          Could be worse, you could be running a 1X. Those funny little chainrings must last, like, 2 weeks.

    • jules

      what you’re checking is chain stretch, which occurs as the connecting pins wear down, allowing the links to stretch apart. if the chain isn’t under tension, then links are not being pulled apart as much. so your measurement will yield a result that suggests your chain isn’t as stretched as it really is and will be as soon as you start pedalling.

  • Andy B

    Don’t skimp on a getting a new chain, its the best BFB upgrade

  • peter

    Does the chain actually stretch or is it the pins wearing down. I prefer using the park tool the measures between the pins . Type of lube is also crucial, I have got 12,000 out of a chain using a product called Squirt without having to change rings or cassette. 10,0000 out of a big rind is shocking , something there is seriously wrong.

    • jules

      I’d guess it’s both that wear down – by chain I assume you mean chain plate.

      I’ve never heard of getting 12k out of a chain. After a ~3-4k mine is past the 0.75mm wear limit. You can keep going for a long time, but drivetrain smoothness and shift quality will suffer.

      • Dave

        And if you let a chain get too stretched, you’ll need to replace the cassette and potentially chain rings too.

      • Dan

        I get >8k from Ultegra chains before they are 0.75% worn. My new bike came with a KMC chain that I got >12k from before it was worn 0.75%. When I looked into replacing with another KMC chain it was ~3x the price of an Ultegra chain so not worth it. I also get 20-30k from cassettes and the only chain rings in have ever replaced across 3 bikes (>100k in total) were FSA chain rings, 1 of those bikes had >60k on Dura Ace 7900 chain rings. I do live in Perth so wet weather riding is limited but I ensure that I lube the chain (Rock n Roll Gold) every 400-800km and make sure no sand/grit is on the cassette and crankset.

        • jules

          that’s a lot more than me. in Melb, wet/grimy riding conditions are a fact of life. I get heaps of life out of cassettes and chainrings as I swap chains as soon as they hit the 0.75 mark, but I swap chains pretty regularly. I do lube regularly, but it’s hard to keep your chain lubed in wet weather as you end up just lubing dirt. obviously cleaning your chain is the ideal solution, but impracticable to keep it clean with the amount of rain we are getting.

          • Dom

            I live in Montreal , Canada and i get about 3-4k(km) off Ultegra and 7k of Ultegra cassette because i decrease completly my chain and drivetrain every five days(i ride everyday). In Montreal, you get all the crazy elements falling on you.

      • peter

        It was definitely 12k ,shifting was still good even under racing conditions. I’ve never had the same results using any other lube or shimano chains , normally I’d get 6 tops. The chain in question was a KMC chain. I do keep my chains pretty clean without being anal about it.

    • Dave

      No parts of the chain actually stretch, you would properly break it before getting to the forces needed to do that.

      All the parts get worn wherever they contact another moving part (e.g. plate-pin interface, pin-roller interface) which creates extra room for movement where a new chain has quite precise tolerances. The slack only gets taken up when the chain is put under tension, hence the technically inaccurate use of ‘stretch’ as a reference to what the chain as a whole is doing.

      • Pete

        How come when you lay an old chain down alongside a new one (of same number links), the old one is longer?

        • Dave

          The individual parts of the chain aren’t any longer, they just have more freedom to move further apart as the contact surfaces (the outside of the pins, and the inside of the holes in the link plates) are worn away.

          A brand new chain has quite a snug fit between the pins and the holes in the plates. Once the pins and plates start to wear, it is just like the result you might expect if you used a bolt that is slightly undersized on some other part of the bike – it would move within the hole rather than being snugly seated.

          This is one of the two primary reasons that you need to clean and lubricate a chain regularly, because old black grease captures dirt and turns into an abrasive grinding paste which accelerates the wear on the chain.

  • Jonno

    Love your bike and it will love you back! I run 2 chains, one gets cleaned while the other is busy!

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