I've been using a chain checker tool (similar to the one in the image below) to determine when I need to change my chain. Right now my tool is telling me the chain is at 50% life/wear.

Yet when I do a search online re: when to replace a change, I'm getting mileage/distance recommendations. Frequently in the 2,000 to 3,000mi range (https://www.bicycling.com/repair/a20...ur-bike-chain/). This seems kind of young/early to me.

So I'm torn. What's best practices? Replace the chain by distance or when the chain checker tool says the chain is at 75% life?

Two years, 857 posts, and you've never seen a chain checker thread?

Chain Checkers are known for showing more wear than you actually have.
I finally got a worn enough chain to use my PARK tool.
It barely fit at .5%.
I took the chain off and measured a 3' section with my scale.
3/32" or .25%.
Is your CC "calibrated"?

...best practice is to measure chain wear with a steel ruler between the pin centers for 12 double links. Should be 12 inches. Chains ought to be replaced before they start to wear the teeth on chainrings and cogs, which are more expensive than chains to replace (mostly).

If the chain is worn, or "stretched" to it's limit, then "distance" is irrelevant, it's just an average amount of life a chain will have. How hard you ride, and how clean or dirty you keep the chain, will affect its period of service. If the chain is still ok, then how far it's ridden isn't necessarily a hard-fast rule, it just puts you in the ballpark.
And, as stated above, I'd go with measuring it, versus using a chain checker. 12" on a ruler or a tape measure is going to be 100% consistent, unlike the various models of chain checkers.

Absolutely use a ruler, my opinion is that chain checkers exist to help sell more chains.

Steel ruler.

Case in point for YMMV == Your Mileage May Vary
Inspect chain and measure !

Digital calipers.

https://www.sheldonbrown.com/chain-wear.html

Scroll down to the section titled Measuring Chain Wear to find all you’d ever want to know about when a chain is bad and how to gage it based on what you’re measuring with the tape measure. Keep in mind you’ll need a tape/ruler longer than 12” to be able to measure the wear.

Steel ruler it is! [MENTION=209177]3alarmer[/MENTION] thanks for the detailed explanation

[MENTION=78399]Bill Kapaun[/MENTION] There isn't much to calibrate on my chain checker. It's just a metal 'ruler' that slots in to the spaces of the chain links.

+1 on the steel ruler. Replace at 12-1/16" per 12 full links, or 12-3/64" if you've got a week-long ride coming up.

I replace chains at 12 - 1/6". But I do not throw them away. I put them in a plastic bag and label them with that length. When new chains no longer run smoothly, I use those 12 - 1/16" chains, replacing them at 12 - 3/32" with other 12 - 1/16" chains until shifting deteriorates. Then it's time for all new cogs and rings. That takes many thousands of miles. And it's probably high time to upgrade to the next number of cogs.

My TiCycles was set up 9-speed in '08. 3 cassettes for two wheels. 12,000 miles. New chains go on just fine.

Steel tape measures work really well. (I typically start at 10" so a stretched chain might be showing 22 - 3/32") Measure front of pin to front of pin.

Ben

My point was to calibrate your checker from experience.I now know that IF my checker "just fits", that my chain is worn .25%. NOT .5%.
Some day I'll learn what the .75% mark really means. Maybe .5%?

There are only three chain checkers that are reliable. Two from shimano and one from Pedro's. https://www.amazon.com/Pedros-Chain-...ateway&sr=8-10
I have the Pedro's because of the price. It is as reliable as a ruler.

https://www.ebay.com/itm/302818236459

https://www.ebay.com/itm/283533481109

Info on the rest. https://www.pardo.net/bike/pic/fail-0...easuring-tools

FWIW, calibration only tells you how accurate (closeness to the truth) and precise (repeatable) a measuring device is. Calibration in and of itself doesn't actually change how any tool measures.

One can also repair or service a tool so that it is more accurate and precise but that isn't really part of calibration. Service often goes along with calibration but it isn't part of what calibration is.


-Tim-

That is correct, though I've noticed that dictionaries will often include the second step of adjusting or rectifying as part of the definition. It seems that as our language evolves it becomes less precise.

Most chain checkers add roller wear to actual elongation, so they exaggerate the wear. When a precision steel rule costs so little, why use anything else? One thing I first found out with campy 10 chains is they can have severe roller and side clearance wear, but show little elongation. I have ridden enough on the 11 or 12 speed chains to know if that's still the case.

If you really want maximum chain and cassette life, alternate the use of 3 to 4 chains, so you're never putting a new chain on worn sprockets. I plan to resume that technique with 2 bikes that have the new Chorus 12 components. All it takes is few hundred miles on a chain to a avoid new-chain skip. I'll also be trying chains from sram, KMC and campy. The new axs chain works.

I'm an outlier because the cheap Park tool is good enough for me. I'm easy on my gear and don't obsess over getting a couple of thousand more miles from a chain. All those little numbers on a ruler....

I don't know if there is a "best practice." If you replace prematurely, you're wasting money and resources. If you replace too late, you're wearing out your cassette and possibly pedaling harder than you need to. The trick is to find a decent balance between the two. I like to err on the side of wastefulness. But I don't usually use a checker, so I can't say at what metric I replace a chain. Take a guess. You don't have much choice.

Yep, and vernier calipers work just fine too, mine measures to .1mm. In fact, I think calipers are more accurate measure of the chain wear. I always measure the new chain right after I've installed it and the variances in different chain brands chains can be up to .3mm over the legnth of chain that I measure. So I calculate the wear limit based on the actual legnth of the chain, not theoretically what its supposed to be.

If digital calipers are used between rollers, you are adding roller wear to true elongation and roller wear can be quite large.

Use a precision machinist's rule and place one end at the edge of a pin. When the pin at the other end is half exposed, you have reached .5 percent elongation.

Why does the ruler have to be steel?

Anything else is cheap crap that won't last. You want a thin machinist's rule. Starret brand is the best.

Neither. Pffft