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I have a park chain checker CC-3.2 which has two sides to indicate when a chain reaches .5% and .75% wear.

However, since I often have some filthy chains due to off-road riding and daily commuting and multiple bikes, I lose track of which ones are worn a little and which ones are worn a lot, Especially after a winter of commuting in salty east coast slush, fine sandy spray from the rainy season, and dirt/sandy stuff flying off my tires from rail trails and singletrack. I've definitely had chains worn well over 1%.

So, Other than performance issues, when neither the .5% and .75% sides of the chain checker fit, how can I tell whether a chain is relatively new (and not well worn) or whether it's really worn (probably past 1%) just using my super basic chain checker?

Does it fit differently or is there anything specific to look for while it's sitting on the chain?

To rephrase: If I have two chains, one with say 0.25% wear and one with 1.25% wear and neither chain allows the indicators on the Park CC-3.2 tool to drop between links, how do I tell the difference? Can I do that by just looking at the park chain checker?

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  • First, make a token effort to clean the chain. Then use the Park tool to check it. If the 0.75 side clears, replace the chain.
    – Daniel R Hicks
    Apr 6, 2018 at 20:51
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    @DanielRHicks the 0.75 percent change interval no longer universal. 11 speed tolerances are tighter, with replacement suggested at 0.5 percent.
    – Rider_X
    Apr 7, 2018 at 6:54
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    The other way to check chain wear is to pull the chain forward, away from the front chainring. The distance that the chain can be pulled away from the ring is a measure of chain wear + ring wear.
    – Daniel R Hicks
    Apr 7, 2018 at 12:12
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    The CC-3.2 will fit into place on both sides if the stretch was 1.25%. It would have to be extremely worn not to fit into place at all.
    – Rider_X
    Apr 9, 2018 at 19:59

3 Answers 3

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As Argenti Apparatus indicated the "go" / "no go" wear gauge such as the CC-3.2 indicates that the elongation has not yet reached 0.5%. If you want some sort of measurement below that (i.e., 0% to 0.5%) you will need to use a different gauge such as the CC-2, measure the inter rivet difference via a ruler, or use a pair of Vernier calipers to measure the roller to roller difference then convert it to a percent stretch.

Using Vernier Calipers

My preference is for the Vernier caliper approach as I could it to give very reliable and repeatable measurements if done right. Methodology can be found in this answer.

inner measurement Example of an inner link measurement (10 links apart)

I use the lookup table below to convert an inter-roller distance 10 links apart to percent stretch (calibration methods can be found here)

chain stretch reference table

Predicting Service Date

I then periodically take a few measurements to predict service dates using a regression approach, such as the example below for a KMC X11-SL chain. As you can see wear rate is fairly linear so extrapolating outside observed data range isn't too problematic (assuming we use the chain under similar conditions). In this case, the regression model predicts it will be time to change the chain at about 3,250 km. If you want to get even more complicated it is fairly straight forward to add confidence intervals to the prediction, then check again at the lower confidence bound.

predicting service dates

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    Loverly graph. I'd be highly curious to know when you rode in the rain, and whether that correlates with periods of accelerated wear (like 550-800 km and 1100-1400 km ) or whether 1600-2100 km was purely in the dry.
    – Criggie ♦
    Apr 6, 2018 at 21:37
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    @Criggie That chain was never ridden in the rain. The deviations from the regression line are likely measurement errors (wear is never perfectly even across a chain). This would simply get captured by the models residual error term.
    – Rider_X
    Apr 6, 2018 at 21:42
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    @Criggie In terms of rain, I never found a huge impact of rain, relative to dusty conditions. If you go back to the answer with the detailed methods the final figures compares three chains, the all have roughly the same wear rates (by duration - average speeds differed so comparison by distance isn't apples to apples), the Tiagra and Ultegra was run in dry conditions only while the XT was run in a mix of dry to rain. If there is an effect is there, it is likely small. If you don't consistently lube in the rain, then maybe.
    – Rider_X
    Apr 6, 2018 at 21:44
  • +1 for very geeky use of Ggogle docs.
    – Argenti Apparatus
    Apr 6, 2018 at 21:48
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If neither size of the chain checker tool will fit between the rollers, the chain is less than 0.5% worn. The Park Tool is not supposed to have more resolution than that.

I personally keep a ride log (relatively easy with Strava and Wahoo) so I know how many miles my bikes have done.

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    It is 0.5% not 5% stretch. If a chain elongated by 5% you probably wouldn’t have any teeth left on your cassette or chainring(s).
    – Rider_X
    Apr 6, 2018 at 20:30
  • @Rider_X Typo fixed!
    – Argenti Apparatus
    Apr 6, 2018 at 20:50
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    Though you do have to pay attention to it. I have seen chains that are worn to the point that the chain checker does not fit. Normally this is easy to tell because the chain is hitting on the inside of the tool rather than the outside, but it's important to be aware of.
    – itfuwub
    Apr 7, 2018 at 16:59
  • @Itfuwub, you should post that as an answer, that was exactly what I was looking for!
    – Benzo
    Apr 8, 2018 at 15:04
  • @Benzo, you should probably update your question to clarify that you have chains that have gone past the 0.5% wear point.
    – Argenti Apparatus
    Apr 8, 2018 at 15:13
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How to identify extreme chain wear on a Park CC-3.2 (or similar tool) with only 0.75 side:

  • Chain is < 0.75% wear, it will hit on the outer edge of the tool and the indicator will not drop between rollers.
  • Chain is >= 0.75% wear and probably chain is < %1, it will drop between the rollers.
  • Chain is probably > 1% wear and worn more than a few percent, likely > 1% wear, it will hit the inner edge of the tool and the indicator will not drop between the rollers.

If a chain is very worn and the measurement gauge hits chain links on the inside edge of the gauge as opposed to the outside edge of the gauge, this can indicate that the chain is well past the .75% wear. This technique can be used to identify whether a chain is heavily worn when you only have a "GO / NO GO" chain checker.

You can see an example of a heavily worn chain showing this condition below (See inner edge contact instead of outer edge contact).

Worn Chain

Image Source: Dalemorrison66 on Instagram

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  • Of course, if your chain looks like the photo, you should probably replace the chain, cassette, and maybe chainrings too... Or just leave it alone until you can change all of it at once, because otherwise, you'll probably have terrible shifting.
    – Benzo
    Apr 8, 2018 at 18:24
  • In an extreme case (if your derailleur somehow manages to maintain chain tension in all gears) you could count the amount of links that fit under the tool in a good chain and compare that to the same on your chain.
    – HAEM
    Apr 10, 2018 at 18:33
  • If this answers your question you should accept it.
    – Rider_X
    Apr 10, 2018 at 22:29

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