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Among tools made by reputable brands, I'd assume that a tool that measures 14 or 15 links (7 to 7.5 inches) would be superior to one that measure 7 or 8 links (3.5 to 4 inches) since the tolerance measured will be smaller.

bike chain checker tool

The number of links that checker tools measure is not announced as part of their description when purchasing online. An in-use picture will enable link counting, but such a picture is not always provided.

Do you really care how many links a bike chain checker tool measures?

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    I gave up using chain checkers. Instead, I feel for play between two adjacent links. If there's play, it is worn. Then I wax the chain, and check again after cooldown. If there is still play, its time to replace.
    – Criggie ♦
    Commented Dec 25, 2021 at 10:21
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    @Criggie Okay, that's cool. But you're basically saying that you are capable of determining by hand whether the play at a single pin exceeds 0.5% stretch, or 0.5 * 25.4 * 0.50 / 100 = 0.0635 mm. That is something that can be done only with deep experience. It's not a recipe for the rest of us, no?
    – Sam7919
    Commented Dec 26, 2021 at 4:19
  • Nope - I never laid claim to accuracy claims. "If I can feel play after waxing then the chain is too worn" You do you - just keep riding.
    – Criggie ♦
    Commented Dec 26, 2021 at 6:35

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It doesn't need many. My Shimano TL-CN41 measures 9 links. My Park Tool CC-4 is slightly longer, 13 links. A visual tool (12 inch ruler) needs 24 links to be reliable thanks to poor eyesight of humans but these go/no-go gauges can be shorter. However, what matters is that the chainwear tool must do its measurement on the same side of rollers.

The problems of chainwear tools that do the measurement on the different sides of rollers are explained here. They include both roller clearance and roller wear in addition to pin wear, whereas good chainwear tools (and the ruler method) measure only pin wear.

The tool that you showed in the picture is one of the unreliable ones. Don't use it to measure chains. It can tell a new chain to be worn, or a badly worn chain to be as good as new.

The only chainwear tools known to be good are Shimano TL-CN40, Shimano TL-CN41, Shimano TL-CN42 and Park Tool CC-4.

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  • Ah! Various pundits argue for the "modern" style of tool, but don't say why. Everything is clear once you mention that one style measures on the same side or rollers, and the other style measures on opposite sides.
    – Sam7919
    Commented Dec 25, 2021 at 9:31
  • This of course begs the question: why are tools of the unreliable variety still on the market?
    – Sam7919
    Commented Dec 25, 2021 at 9:35
  • @Sam There are many bad products on the market. Bike tools aren't unique.
    – MaplePanda
    Commented Dec 25, 2021 at 22:45
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You need to define reliable, I argue even the most budget tool on the market is good enough.

Ask yourself what is the chain tool measuring? Hell does not freeze over if a chain the measurement has a large percentage of error. The tool needs to be accurate enough to tell the operator the chain needs replacing or not, and what some argue as 'unreliable' are accurate enough to do the job.

If you made a chain tool more accurate, what extra knowledge do you gain and more importantly what are you going to do with that knowledge? Are you going to measure more often now you have more precise measurements? Time to replace is also not a precisely defined thing - some time between X and Y, where X and Y are much bigger than the tolerance of even the cheapest tool.

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