I have changed one chain already. This photo is the second chain. This is wear indicator. I’m using a 9 speed system and the chain don’t bite well with cassette sometimes when changing to large cog. Do I need to change the cassette and chain? Or just chain solely? In every of my ride i do launch control. enter image description here

  • 5
    Measure again without the quick link in the section measured.
    – mattnz
    Nov 27, 2021 at 5:01
  • Also: measure at different spots, 3 to 4 times along the chain. I change if two out of 4 show .75%.
    – Carel
    Nov 27, 2021 at 10:58

2 Answers 2


You mention this is your second chain. I assume that means you’ve worn down the first one and replaced it once the 0.75% wear indicator slipped through.

Usually cassettes will need replacement after 3 or 4 chains. A lot of it depends on which sprockets you use most. The bigger sprockets have more teeth, therefore more surface area and wear down slower.

If you have trouble with your drivetrain on the second chain already it’s more likely to be an issue with the rear derailleur. It could be bent, the cables and/or cable housing could be worn or most likely it just needs adjustment. I would also check the chain for stiff links.

  • Yes, I often have to lube derailleur cable if not it won't shift properly, however sometime if i pedal 1000watt down it will just slip between gear jumps
    – Ygovec loh
    Nov 28, 2021 at 4:29
  • 1
    Does something slip (is it actually the chain?) or does it start climbing to the next sprocket under load? Lubing cables is more a quick&dirty short term solution. You should probably replace the whole cable+housing.
    – Michael
    Nov 28, 2021 at 7:13
  • 2
    Agreed but a minor point: if something is bent, it's a lot more likely to be the RD hangar rather than the RD itself. And the hangar can be bent back or replaced, whereas if you managed to bend the RD pulley cage, that's very hard to bend back, and replacement cages are pricier than hangars.
    – Weiwen Ng
    Nov 28, 2021 at 15:29
  • 2
    @WeiwenNg is probably right for higher-end derailleurs with lightweight (i.e. brittle) pulley cages, but I've unbent many cheap derailleurs with steel cages using just a crescent wrench and sometimes a vice. Kids will habitually drop their bikes on the rear derailleur.
    – Rich Moss
    Dec 2, 2021 at 19:41
  • @RichMoss Good to know.
    – Weiwen Ng
    Dec 2, 2021 at 19:48

Not so fast!

There are only two tool series that measure chain wear accurately. They are Shimano TL-CN series (TL-CN40, TL-CN41, TL-CN42) and Park Tool CC-4 (warning: other Park Tool CC tools like CC-3 are crap). Your tool does not look like it's from either of the two series.

Chain needs to be discarded when it's past 0.5% limit. This means the chain length is 0.5% longer than it was when it was installed. The chain length must be measured from pin to pin, or from roller to roller at the same side of the rollers. I suspect your tool belongs to the bad 99% of the tools category that measures at different sides of rollers, and not to the good 1% of the tools category that measures at same sides of rollers.

If you measure at different sides of rollers, then you are measuring both roller clearance and chain wear at the same time, and the measurement is sensitive to roller diameter.

If you measure at same side of rollers, then neither roller clearance nor roller diameter enters into the equation. All of Shimano TL-CN40, TL-CN41, TL-CN42 and Park Tool CC-4 measure at the same side of the rollers.

Only Shimano TL-CN40, TL-CN41, TL-CN42 and Park Tool CC-4 measure pure chain wear instead of measuring a combination of chain wear, roller diameter and roller clearance.

Thus, only Shimano TL-CN40, TL-CN41, TL-CN42 and Park Tool CC-4 give accurate wear results. The Shimano tools don't say what is the wear limit measured by the tool but I suspect it's 0.5%. The Park Tool CC-4 measure 0.5% and 0.75% wear, and out of those two, you should be using 0.5%.

All other tools can tell a massively worn chain to be good if you're unlucky, or they can also tell a completely new chain to be past the wear limit if you're unlucky.

Your tool also has the flaw that it seems to have only 0.75% and 1.0% measurement points and no 0.5% measurement point. The 0.75% and 1.0% measurement points are not what the tool suggests they are, because they are not measuring only chain wear, but a combination of chain wear, roller clearance and roller diameter.

If you don't have any of these tools, you can use an inch ruler at least 12+1/16 inches long. In practice this means much longer than 12 inches. 12 inches is not enough unless you "extrapolate" the location of the 12+1/16" mark. A ruler also requires good light and good eyesight.

Source: http://pardo.net/bike/pic/fail-004/000.html

  • .5% is the limit for 11s and higher systems. For 10s and lower, it is .75%. parktool.com/blog/repair-help/…
    – Weiwen Ng
    Nov 27, 2021 at 12:42
  • The contention that roller diameter matters is correct, and SRAM’s 11s and especially 12s chains use larger diameter rollers than others. The thing is that the OP is on 9s and it looks like a Shimano chain. Their gauge is likely to be adequate.
    – Weiwen Ng
    Nov 27, 2021 at 13:39
  • @WeiwenNg The point is that roller diameter and clearance are not as tightly toleranced, and the variance could lead to measurement errors. Some chains are also just looser than others in general, again adding confounding variables.
    – MaplePanda
    Nov 27, 2021 at 18:28
  • 1
    Perfection is the enemy of good. Most people don't know what a chain measuring tools is, let alone use one. Using one that in theory si not as good as the best does not make its use bad.
    – mattnz
    Nov 28, 2021 at 3:03

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