Chain wear indicator tool for "screening"?
 

There's probably a million threads on this very question, but I couldn't figure out how to search for it.

Short version: Is a chain wear tool a valid screening tool - does it err on the side of falsely indicating excessive wear (good for screening) or the opposite - tricking you into thinking the chain is OK when really it's worn (bad for screening)?

Long version: I totally understand that it is cheap and easy to measure chain wear using a steel ruler and the 1/16" elongation criterion. I can do that. But I also understand that it's best if the chain is under at least a little tension (i.e. hanging from a nail or manually stretched out.

I also understand that using a tool is dead simple but might not accurately measure real chain wear (I can't explain to you why but when i read explanations, it makes sense, so there).

Finally, I also think it's a hassle with poor lighting and only two hands to do a truly accurate measurement with a ruler while a chain is on the bike - pulling the chain in tension, holding the ruler precisely and sighting a 1/16 measurement. Not impossible mind you, but more of a hassle than just using the chain wear indicator tool ... again, while the chain is on the bike.

In my family of fairly active riders, I have about a dozen chains I need to keep track of, mostly on bikes but also a couple of spares I rotate in. I have a Park chain wear tool and a steel ruler. Yesterday I did a spot check of a couple of chains on the bikes with the Park tool and also the spare using the tool and a ruler (which has similar wear).

I did 2-3 checks on each of the chains I checked with the tool on the bikes. A couple of chains were totally "OK" with the tool at every test site. A couple were OK at two sites, but showed ".75%" wear on a third. In other words, those chains could have shown "OK" if I'd only checked once.

This is where the question comes in. If the indicator tool shows wear, I'm thinking then I'd take the chain off and do a ruler test to confirm. But, if the indicator tool doesn't show at least "75%" wear, I'll just lube up the chain and we're good to go.

What do you think?

Thanks.

I remove my chains to clean them. I check them then.
. I have a Rohloff chain gauge that I use until it shows a worn out chain. I then use the ruler method until the chain is actually gone. I bought the gauge before I knew that it is not accurate because it measure the rollers and the chain. Not the best way.

Sounds like a good plan to me.

I do find myself wondering why a chain would wear differently in different spots, but it could be a difference because of the manufacturing tolerances that allows one portion of the chain to be flagged as worn earlier than other parts of the chain in some cases. Or possibly that a pin or link is slightly softer than others (again related to variances in manufacturing process. It could also mean that at some point(s) lubrication ws not done uniformly.

In any case, if a chain checks good on one section, and fails on another, I would consider the chain "almost worn" for practical purposes.

Based on your findings, I plan to use my indicator on a chain. If it shows good, I will keep using the chain. If it shows as ready for replacement, I will check 1 more spot. If it shows worn, I will replace the chain. If it shows ok, I will assume it is borderline and ride on... With my history, I assume that I can misread a ruler far more easily than make a mistake with a gauge constructed specifically for the purpose.

Your risk and/or cost avoidance priorities and history of accurate or inaccurate measurements may lead you elsewhere for your decision process.

More accurate .. KMC makes a digital chain wear indicator How to minimize chain wear

seen here .. too KMC Digital Chain Checker : Fairwheel Bikes, Cycling Boutique

Yes, but as OP is asking, that is a false positive, so it is safe. Also that is only true once the tool can be squeezed between the pins. As long as the second tab is not fitting between the pins, the measurement is accurate. In other words, until the tool is stretching the chain against all the internal parts, it is just as good as a ruler. Also once the chain is really way too long and the tool fits between the pins with no stretching, the tool is once again as good as a ruler. It is only when the tool is stretching the chain in order to hook it at both ends that is gives a false high reading. So you can just wait until the chain is long enough to be a little loose on the smaller, more conservative scale of the tool. Simple, huh?

In my experience the checker gets very loose before the chain is gone.

Sounds like a lot of work to save a dime. Of course the total amount of currency involved could be lesser or greater I guess... but ether way it can't be much.

Of course in my calculations I don't use specialty finished 11 speed chains or anything like that. My KMC chains purchased via Amazon aren't much more than about ten bucks. So if I repeatedly replace the chain about ten percent too early.... every decade it would amount to a whole new free $10 chain. Of course a less than perfect measurement/replacement procedure would more likely mean a five percent ether way error. Early replacements would cancel late replacements.... and little to nothing would change.

I don't know why cyclist fret so much about the disposable parts.

exactly.

I sure hope you don't think I'm "fretting".

I'm simply asking - from someone who might know and explain - whether the tool gives a false positive or false negative. I'll leave it up to myself and others to decide whether to "fret" about the hassle of chain wear methods or chain replacement.

Myself? I don't sweat a few bucks here and there to save time and effort. But, I don't think it's so dumb that with about a dozen chains to keep track of, it's worthwhile to have a dead simple and quick screening tool as long as I know which way the potential inaccuracy goes.

IMO, as you describe it, they're excellent for screening since they read false high.

Exactly.

Yep, my Park CC3 does tend to over report chain wear as the 0.75% tab will fit when the 12" ruler says 1/16" (0.5%) or less. As to checking the chain under tension, just use the ruler on the lower run of the chain while it's installed on the bike. The rear derailleur spring will keep it plenty tight enough for a good reading.

IME, measuring a chain is a waste of time. until the drivetrain skips, it is alright as far as i am concerned. when the drivetrain skips, i start with the rear cog(s) first, then the chain, and then the chainring.

twelve replies and countless threads on this issue has wasted more people's time and money than i care to think about. i'm a little disappointed that what i otherwise consider to be clear thinking, well informed individuals on this forum are drinking the kool-aid on this issue. is suspect it's a genetic "a tool for everything" thing involved here. :)

I tend to do the same thing as I will wear out a chain and cassette together and replace both. But I'm using lower line chains and cassettes. If I were using Record or Dura Ace cassettes at about $300/each I wouldn't be nearly so cavalier about letting the chain wear to the point it damaged the cassette

What kool-aid? Sure there are "tools for everything" and if a 12 ruler is a "tool" to quantify chain wear, what's the harm?

Fret: verb (used without object), fretted, fretting. to feel or express worry (like post about it on the Internet?), annoyance, discontent.

Yeah... I guess I was implying that most or at least many cyclists (not just you) fret the wear of what are disposable parts. But I didn't mean it as any form of insult or put down... I promise. Sorry if my wording wasn't as friendly sounding on your side as it was intended to be... from my side.

I read a post the other day about a guy who gets 20,000 miles (or was it km) out of a chain, cassette, and front rings, because he never changes them until he absolutely must, and then all together. The economics of this plan are indisputable. The only downside I can see is if you need to swap in a wheel with a different cassette that isn't worn in like the one that is part of the system. Then you have trouble.

i agree, there are some drawbacks. but despite being cheap, selfish, and a poor dresser, i do it because it's so worry free.

to be honest i rarely have a chain or cog wear out, let alone a chainring, although i ride about 7000 miles a year spread evenly across six bikes (it could be because i live in a benign climate and wipe down and oil the drivetrain before each daily ride). but i've been buying new chainrings and chains at an alarming rate recently, mostly because i've decided to run higher gears. the noise generated by a new chainring and even slightely used chain annoys me so i oftentimes just get a new chain too. SRAM pc-1 chains are surprisingly inexpensive.

The chain checker as a pre-screen is a good idea as long as you do it frequently enough. If, like me, you let it go another 500 miles at the end of the winter, not so good. :(

It's quick and easy, works well in a poorly lit garage, and I'm going to do that tonight!

Um, no. Once the cogs start to skip you ruined the cassette. You can't use that wheel in another bike or use a wheel with a good cassette on your bike. By checking chain elongation regularly, my cassettes last thousands of miles. I go through at least 7 chains before I have to replace the cassette. Chains (KMC) is cheap, cassettes not so much.

Or you can just never change the chain and cassette. That will last you easily ten years or so with normal miles, but you can never put a good wheel on your bike because it will skip.

Actually I just realized there is another problem with the just keep using the chain, cassette and front rings all together until you absolutely have to change them out. If you ride mostly on two or three cogs as I do in pancake flat Houston, it is like having two differently worn cassettes mounted at the same time. If I were to let the chain, cassette (say the three most used cogs) and chain rings all wear in together significantly, then maybe took the bike to the mountains or had a really strong wind day, I would be in trouble. Using relatively new higher or lower cogs than the usual three would not work well with the worn chain. I guess there are reasons why folks frequently replace their chains, less so their cassettes and even more rarely their chain rings. Damn!

Cool! I tried to use my 6 in dial caliper, but I don't know the roller inside to inside dimensions to check. Is it the same on chains independent of the manufacturer? IF so I could obsessively measure my chains to my hearts delight.

I might have been a little testy, but I actually agree with you in that I really don't care if I get 100% of use out of a chain and cassette or ditch it a little prematurely.... or get a little less usage than possible because of poor habits or less than obsessive maintenance. This definitely goes for my cleaning/lubrication standards - I regularly lube, but rarely clean the chain other than running fresh lube through it and wiping it thoroughly.

They are indeed wear parts and the marginal difference in cost between being compulsive and just "reasonable" is negligible, to me.

So, really, I wasn't fretting - not worrying, not being discontented or annoyed. Just curious about the screening value of the tool - which I think it does have that value.

At my rate of riding in a mostly dry climate, only about 2,000 miles per year (short summer season, not a winter rider) divided between three main road bikes..... well, chain and cassette wear is just a non issue, except there's several more bikes in the family that I get "ready to go" every spring and any time I can save a minute it's worth it!

Thanks to all for the advice. Conclusion: it's a screening tool that gives false positives (indicating more wear than actually exists).

Sounds about right to me.

I can't imagine maintaining a family sized fleet of bicycles. Do you just wait for complaints or do you have scheduled inspections? I assume you have tools and do your own work.

I plan on getting one in the not too distant future for exactly that purpose.
I flip a few bikes on CL and have 2 of my own. A quick "yep, it's OK" gauge" I expect would be handy, instead of trying to read the ruler while holding a magnifying glass with one hand and keeping the pins aligned to the 0 & 12" mark with the other two.

Using the gadget for screening makes a certain amount of sense, but why remove the chain to confirm with a ruler. It's easy enough to pull the RD back to get a taut section over a foot long in the lower loop which you can then measure on the bike.

Remember that measuring stretch isn't a precise measurement of the chain's condition, it's only an indirect indicator, so serious precision is meaningless.

The best explanation of chain wear measuring tools I know of is this:
http://pardo.net/bike/pic/fail-004/0...easuring-tools

The bottom line is that he finds commercial chain wear measuring tools are conservative in their wear estimates. But also that almost all of them includes roller wear in their measurements instead of just measuring pin wear.
A tool series that only measures pin wear is Shimano's TL-CN40/TL-CN41 and the new TL-CN42.

A number of years ago at one of the industry shows (East Coast, Philly I think) I asked the SRAM (actually IIRC they were just Sachs then) guys much of this same question. Their answer was that the manufacturing tolerances were loose enough (with all brands they tested, not just SRAM) so that you'd get a range of "measurements" on even new chains along the chain's length. I know I've gauged (and this is what most wear indicators do) new chains and gotten readouts suggesting much wear.

Still we use chain wear gauges at work daily. To some degree I feel there is an aspect of judgment at play. This is why i prefer to use the same gauge each time I check a chain. Andy.