dgracer

I have one of those Park tool chain wear indicator with 0.5% and 0.75% wear indicator marks. It is a 'go/no-go' tool, so you do not know how much between those marks the chain is worn. The Park website says the 0.5% and 0.75% marks are where most manufactures suggest replacing the chain. So at which wear mark should I replace the chain? The tool 'goes' the 0.5% mark into the chain; and the 0.75% is still a no-go, so my chain is somewhere between the two at the moment. Do I need a new chain or should I wait for the 0.75% to 'go' with the tool? Strangely, I measured the chain and it is exactly on the 12 inch mark, so if I was checking wear that way I would not know the chain was worn at all!
DG.

mconlonx

We have a chain wear indicator which is the .75 and 1.0, go/no-go version. At .75, we suggest a new chain; at 1.0 we say a new chain is needed.

digibud

If it's still measuring 12 exactly I would personally not replace it.

GeneO 

Most wear indicating tools, including that Park, are not very accurate because there is play in the rollers on their pins. The tools push against the rollers in opposite directions, moving the rollers away from each other and up against their link pins, giving an inaccurate reading. I think the best way is to measure the length under tension.

Shiseiji

Gene, sorry but I respectfully disagree. I don't think most of us could detect a 1% wear in the length of a chain and that's after making the assessment that the pin/plate wear is as good to measure as the pin/roller interface. Given how a chain works, personally I would go with a higher wear between the pin/roller than pin/plate.

Checking the pin/roller wear is the purpose of the gauge and it is accomplished by pushing them away from each other using the tool as a leaver. The interference between the pin and roller is the known start point for the "Go" part of the test. If the pin/roller interface changes due to wear, that's what the gauge picks up when the .75% leg falls in the link. The pin/roller interface has worn .75%. At 1% wear the chain should be replaced. If the gauge doesn't fall in, the wear is less than .75&

Putting the chain under tension pulls the plates, but then you have to be able to use "something" to measure a 1%, or what ever you have decided is acceptable, wear. Take a look at the chain pictures here: https://sheldonbrown.com/chains.html to see where the wear is. It isn't where the pin is in contact with the outer plate.

No mechanical device is going to wear evenly. That's why in a chain one link set may pass and another fail. It probably isn't an inaccurate tool. After that the old saying "A chain is only as strong as it's weakest link." applies.

if you have another explanation, I'd like to hear it.

Al1943

Often (not always) .75 is as far as you can go without replacing the cassette. In some cases .65 may be the max.

LesterOfPuppets

1/8" over 12" is just over 1%. I like to replace at 3/32". Works pretty well for me.

GeneO 

You can put one of these gauges on a perfectly new chain and it will show some wear (I have tried the Fiskars) because of the play in the rollers on the pins. I think it is safe to assume that for different chain models/brands a new chain will measure different wear, depending on how the chain is constructed. So if you go by the a gauge that has a go/no go how can it be accurate?

I think chain stretch *is* the important thing to measure. That must be what mainly leads to wearing the cogs and chain rings - if wear has caused the roller to have a larger diameter or the pin a smaller, it won't unevenly wear and hook the cogs.

I can see 1/8" stretch or even 1/2 that.

Shiseiji

Yea, I should have done the math,my bad.

I keep thinking my way through this, and best I can come up with is that what you are saying is that the inner plate, even with a bushing, is the least hard metal and that's what gets worn first.

More so than pin wear under the roller.

Is that what I'm hearing?

Follow up question. For lack of a better term, what about side to side flex, i.e. from too much cross chaining?

GeneO 

I try and properly maintain my chain so it doesn't wear the cassette and chainrings. The cassette is an $80 item, the chain $30. so I only care about how the chain might impact the life of my cogs/ chainrings. I also try and not cross chain so I don't wear out he cassette and chainring (not the chain).

Looigi

I disrespectfully agree. Here's a web page that explains it. https://pardo.net/bike/pic/fail-004/000.html

I've spoken with a manufacture of one of these types of gauges and they agreed that it was bogus.

GeneO 

Why are you dissing me

rydabent

I would suggest the proper way to use a Park tool is to measure at several places along the chain, now just one point.

Fred Smedley

If I am measuring with a ruler, what kind of tension is applied to the chain to get a accurate reading? Derailleur tension on large chainring or stretched tight as possible on a table ?

Crankycrank

Measure with chain on the bike, use hand pressure on the pedal to pull the chain taut. Using the large chainring makes the chain easier to measure from and choose a rear sprocket that gives a fairly straight chainline.

rsacilotto

Looigi, I'm a little confused - when you say a manufacturer agreed that "it" was bogus, are you referring to the article? If so, and they agreed (with you, presumably) that the article was bogus, then why do you agree with GeneO regarding the inaccuracy of the tools and link to the article supporting that stance?

Regarding the article, it was very interesting, but didn't quantify the roller wear error that was claimed to be causing the inaccuracy. What is a realistic roller wear factor and what is its effect on the measurement? If roller wear is .1mm (roughly .004"?), and you double it to cover both sides of the tool, and a tool measures 4", then the error is .008" or .2% - this seems significant, .75% on the tool could actually be .55%. If the tool measures 6", then the error drops to .13%. Is .1mm a reasonable factor? Do I have the math right?

This all being said, I just measured one of my chains. By measuring pin distance with a caliper, the chain has stretched .24% (5.012" over 5 links) , but the go/no-go tool indicated 1%... even if the caliper was a little off, that seems to be a big difference.

Crankycrank

I've seen a few debates about different chain measuring tools and their accuracy. From what I have seen it may depend on brand of chain/tool and type of riding you do. I'll just say that I bought one the Performance brand tools after my neighbor let me try his. I use a KMC 10.93 chain and have used a ruler and the chain tool together quite a few times and both seem to give about the same measurement. This of course is only valid for this combination of chain and tool but if you have some kind of measuring tool try using a ruler along with it until you can figure out if they match. I think the tool is so much easier to use and would rather ditch the ruler. Just my 2cents.

skoda2

GeneO has it right, compared to cassettes/freewheels, and chain wheels , new chains are inexpensive. It's not rocket science,
Just replace the chain often, keep it properly lubricated, and you're good to go. Your expensive components will thank you for it.