So how worn is your chain? Is it so far cooked you’ll need a new cassette? Or is it simply an old chainring telling you lies with the method described in the previous article?
You’ll need a tool to know for sure.
What is there to measure?
During each articulation around a chainring, cassette or pulley wheel, the eight pieces that make a full chain link are experiencing an enormous amount of friction. It’s easy to see how and why chain lubrication can play such an important role in efficiency and durability.
With each articulation, the riveted pin remains static, with the same surface repeatedly seeing friction. Similarly, the roller is held static when in contact with a cog – it doesn’t roll. As a result, it’s the inner link plates that are articulating around the static pin.
As the inner plates articulate around the pin, the pin is worn thinner, and the inside bores of the inner links expand. This wear leads to play between the pieces, and when the chain is pulled under tension, its length grows. This is elongation wear (aka, stretch).
Wearing of the inner and outer plates, known as lateral wear, is also a key factor to consider. This will see the side-to-side play in your chain increase, and with it, you’ll experience slower shifting as the derailleurs and shifting ramps work harder to pull the floppier chain onto the desired cog. It won’t lead to the wear of other components, but it will stop your shifting from working at its best.
How to measure the chain wear?
There are quite a few methods to measure the chain wear. Starting with simply pulling the chain of the chainring, through drop in checker tools, ending at digital checkers or calipers, or even measuring chain elongation off the bike.
Most of them can be an overkill both costwise and hasslewise, so as per Adam Kerin of Zero Friction Cycling suggestion:
“As a general rule, I prefer a quality drop-in chain wear checker. For those playing at home, checking wear via measuring elongation with calipers, a ruler, or hanging the entire chain is fraught with some challenges. Chain wear checking needs to be something simple and quick, so that users stay on top of and replace chains before they become too worn and start eating into expensive cassettes and chainrings.”
Therefore, we will focus this article on the simple fixed-length, drop-in style tool that will quickly give you a go or no-go gauge on your chain wear.
Get to know your tool.
Drop in tools attempt to measure the distance from one pin to another, however, as it sits against the front of one roller and the backside of another, its reading can be thrown off by the rollers.
This shouldn’t be an issue, but not all rollers are created equal, and it’s common to find some chains that have rollers that are looser-fitting, faster-wearing or simply different diameters than others.
Because of this, some chain wear checkers seek to isolate the roller wear from the measurement and do this by measuring from equal, and not opposing, sides of the rollers.
These should provide a more consistent reading across a greater variety of chains, even if they’re still impacted by roller wear and roller variances (just to a far lesser degree).
Replacement points.
If a chain is worn, the tool will drop into the link and sit flush along the chain. Or if it’s not worn, the tool will sit above the link, as shown in the photo above.
The .5% marking is a recommended replacement point for 11 and 12-speed drivetrains, or as a warning for those on 10-speed or lower setups. The .75% reading is the suggested replacement point for 10-speed and lower. Some tools offer a 1% wear point, too, something best kept for eight-speed chains or lower.
This .5% recommended replacement point is fairly new and comes from an increased understanding of how the narrower cogs of modern drivetrains offer less surface area and are therefore more prone to material wear.
Because of this, many older chain wear checkers on the markets are outdated, and will simply show chain wear on newer drivetrains at a point that’s too late.
Using the tool.
It’s important to know that chains rarely wear evenly across their entire length. And so, however you choose to measure your chain wear, you should do it across three to seven separate sections and use the highest measurement or average across the readings.
And avoid including the quick link or similar joining link in your measurement, as these often have slower wear rates.
The amount of tension applied to the chain, and how dirty it is, will impact the reading with any tool used. A dirty chain will likely always read as being less worn than what it really is, likewise for a chain doused in a thick lubricant. While the more tension you put on the chain, the more worn it’ll read. And this is where things can get tricky.
It doesn’t make a whole lot of sense to clean a chain prior to replacing it, but just know that the grittier, greasier and grosser your chain looks, the likelier it’s more worn than what the tool tells.
Chains are never ridden without tension. After all, that’s how it interfaces with a cog in use, so with most checker options you will need to create the load separately.
Here’s an easy technique. With the rear wheel held in place (easiest if it’s on the ground), pull on the crank until any easily discernible slack in the chain is taken up. With the chain wear tool in the top-span of the chain (above the chainstay), check whether the tool drops into its wear mark. It’s far from scientific, but it’s quick and relatively repeatable.
Most tools will simply drop into place if the chain is worn, and so only ever apply a light load to the tool, and never force it. If you’re having to push down on the tool with any level of effort, the chain is not worn. Chain and tool tension can greatly impact the effectiveness of any chain wear indicator. With that said, we do find that if you push hard enough the tool can and will flex, effectively forcing it into an otherwise new or not-yet-worn chain.
Summary
According to Adam Kerin of ZFC, if you keep up on your chain maintenance, use a good lubricant, and replace your chain before it shows significant wear, then you could get as much as 50,000 km from your chainrings, so...
1. Get yourself a trusted chain checker tool and use it often.
2. Know what is your tool measuring — equal or opposing rollers? Adjust respectively.
3. Establish your chain’s replacement point, basing on the drivetrain set-up.
4. Apply load to the chain for the measurement.
5. Measure across 3-7 different chain sections and average or pick the largest measure.
6. Know that a dirty or over-lubed chain will read less worn as it really is.
7. Do not force your tool to fall into the link.
8. Don’t be afraid to replace your chain when you think it’s time. Your drivetrain will thank you.
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Know How Division
To explore related topics such as how different riding conditions affect chain wear, tips for chain cleaning, and comparisons of chain lubricants, check out other articles in our blog. These posts dive deeper into maintaining your bike chain in varying environments and offer advice on prolonging the life of your drivetrain.