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Tin Man
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69 Posts
Discussion Starter · #1 ·
My Sette gauge shows .75mm of stretch on the entire XTR chain. The 1.0mm side falls into the chain at a few points on the chain. My new M981 chain with the slick coating showed up yesterday.

The question...should I squeeze as much life out of the old chain as I can? If I run it longer do I run the risk of tearing up the sprockets or breakage?

FWIW...I am pretty anal about chain maintenance. I clean and lube almost every ride, especially when it's wet.

SLX 2x10 HT

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Trail Tire TV on blogger
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didn't know Sette made a chain gauge.. many aren't really good for checking depending on how they work.. though a proper one is still better than the common measuring with a ruler, which is better than nothing at least.

anyway.. better to use the new chain,.. I often save the old one though as when the cassette and rings start to wear down, an old chain can still be used were a new chain may no mesh to the wore gears.. granted you should change the rings/cassette at that point, but I've gotten another year of flawless shifting out of old worn chain and rings.. just have to keep an eye on it all. Actually wore through a chain's inner roller in a few spots.. still worked though.. :p but at that point it's time to replace EVERYTHING... :rolleyes:
 

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Tin Man
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69 Posts
Discussion Starter · #3 ·
Actually, I have a dial caliper, I could just compare measurements from new chain to old and then compare that to the gauge reading.

Still like to know what the wear limit is on a chain. I'll do some searching. -ted

sette.jpg
 

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A ruler works fine too, when a chain measures 12 1/16 pin to pin it's time to change it. I haven't used that Sette but if it's like others of the same type you should replace your chain now.
 

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Tin Man
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69 Posts
Discussion Starter · #6 ·
My gauge measures inside to inside. The digital one looks like it's the same. Makes sense, measuring this way will pull the chain out to get "stretched" measurement.

gauge.jpg

JB, Just read that elsewhere. I never realized that link to link was exactly 1".
 

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Trail Tire TV on blogger
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I know there are a mess of people here who use the "ruler" method and swear by it.. but it's really not that accurate. I've been doing fine carpentry for 30+ years and can tell you that your line of sight can change a measurement drastically. And we're using much tighter tolerances with the chain than with wood working.... this image is just a general reference.. and far from scale, but gives the idea..

chain-stretch-measurement.jpg
 

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I know there are a mess of people here who use the "ruler" method and swear by it.. but it's really not that accurate.
I agree that measuring chain "stretch" this way takes a bit of skill and is easy to get wrong but I disagree that it's inherently inaccurate. Done correctly, with a steady hand and moving your eye so it is perpendicular to the pin when taking measurements, I think it is the benchmark of all measuring methods. I have always calibrated any chain checking device I use by seeing how it compares to the ruler.
 

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Tin Man
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69 Posts
Discussion Starter · #10 ·
I appreciate the input but I'm just not on board with a lot of it. Just about every chain gauge in creation measure inside to inside. IMO the purpose of the gauge is to measure chain "wear"... be it stretch, roller wear or both. So as long as the old chain is measured the same way a new one is the measurement will be accurate.
 

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Trail Tire TV on blogger
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I appreciate the input but I'm just not on board with a lot of it. Just about every chain gauge in creation measure inside to inside. IMO the purpose of the gauge is to measure chain "wear"... be it stretch, roller wear or both. So as long as the old chain is measured the same way a new one is the measurement will be accurate.
actually, no.. "wear" to some point has no effect on the chain.. as long as the center-to-center pressure point stays the same. So if every roller wears 16th on an inch, the area where the gears come in contact with the chain stays the same, 1 inch center to center as they have all shifted the 16th the chain will still mesh properly with the rings.

plus with rigid chain tools like the Sette you have, many chains use different tolerances in the roller play depending on the type of pin and material used for the roller. A brand new chain can read already over stretched if you push the roller out on one side and in on the other if it uses a harder material roller which is often thinner with more play. More play allows the chain's roller to line up easier and quieter to the next ring when shifting as well as allows for better alignment with newer high range drive trains that depend on a LOT of chain flex.
 

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> /dev/null 2&>1
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Measuring inside is just as effective as measuring outside, because the primary mechanism of "stretch" isn't actually stretch - according to the venerated Mr Brown:

http://sheldonbrown.com/chains.html#stretch

"Cyclists often speak of chain "stretch", as if the side plates of an old chain were pulled out of shape by the repeated stresses of pedaling. This is not actually how chains elongate. The major cause of chain "stretch" is wearing away of the metal where the link pin rotates inside of the bushing (or the "bushing" part of the inside plate) as the chain links flex and straighten as the chain goes onto and off of the sprockets. If you take apart an old, worn-out chain, you can easily see the little notches worn into the sides of the link pins by the inside edges of the bushings."

When doing internal measurement, yes, you are measuring roller play, but, this same roller play is what elongates the contact zones between the chain and the cassette, causing that grinding on the leading edge of the cassette tooth, eventually shark-toothing the cog.

When measuring outside the chain with a ruler, you are measuring the same thing, but in a different way. I personally feel that ruler measurement is a little less accurate because you need to eyeball judge a relatively small dimension.
 

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Magically Delicious
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I know there are a mess of people here who use the "ruler" method and swear by it.. but it's really not that accurate. I've been doing fine carpentry for 30+ years and can tell you that your line of sight can change a measurement drastically. And we're using much tighter tolerances with the chain than with wood working.... this image is just a general reference.. and far from scale, but gives the idea.
Your 'line of sight' point is well taken. However, perhaps what woodworking techniques and standards lacks on mechanical objects can be easily achieved with some fabrication and basic machine shop measuring skills. Using a simple engineers rule and uncomplicated basic skills can yield superior accuracy over a chain gauge. One can use a budget caliper (in or out) for reasonably tight tolerances in center-to-center pin measurement.
 
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