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Old 08-26-12, 07:22 PM   #1
ducati hyp
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Chain stretch

Hi, I have a parks chain checker and my chain still doesn't indicate it needs changing (.75) BUT I'm not about to trust that tool , so I measure 12 pins with a steel ruler and see if there is 1/16" stretch and from pin center to 12 pins over and i'm at the center of that pin (6" ) this is after 3000 miles . Is it possible to have almost no stretch after 3K miles ?? Yes I did check in a few spots..
BTW my chain is a shimano 6700
One ? is when new is 12 pins center to center 6" even ??
Also what are you getting for miles out of your chains ?

Last edited by ducati hyp; 08-26-12 at 07:24 PM. Reason: add
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Old 08-26-12, 07:46 PM   #2
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Yes, each full link is 1" long and each pin will line up perfectly with every 1/2" mark when the chain is brand new.

You measure a 12" section, and if it's longer than 12-1/16", then you replace the chain.
Sheldon brown's site could be a bit more specific about that, actually.
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Old 08-26-12, 07:50 PM   #3
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Yes, each full link is 1" long and each pin will line up perfectly with every 1/2" mark when the chain is brand new.

You measure a 12" section, and if it's longer than 12-1/16", then you replace the chain.
Sheldon brown's site could be a bit more specific about that, actually.
is it 12 pins = 6" with no more than 1/16" of stretch OR 12" with no more than a 1/16" stretch ?????????
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Old 08-26-12, 07:51 PM   #4
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... 12" with no more than a 1/16" stretch ?????????
This
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Old 08-26-12, 08:00 PM   #5
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This
That would be hard to do while the chain is on the bike and if done off the bike it would be tough getting good tension on the chain..
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Old 08-26-12, 08:12 PM   #6
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That would be hard to do while the chain is on the bike and if done off the bike it would be tough getting good tension on the chain..
You don't need serious tension on the chain, just enough to take up all the slack. Also there's no magic rule about 12". It's just convenient because 1/16" over 12" is just about equal to 1/2% which it a guide. If you prefer to measure 6" then ti's 1/32". As you see, there's an advantage in measuring over as much distance as possible. Many riders remove chains, hang them on a nail and measure over 4' (96pins) and replace at 1/2".

If you want to measure on the bike, one easy way is to measure the lower loop. Pull the chain back at the lower RD pulley an measure up toward the chainring. The nice thing is that there's no seat stay of FD cage in your way, and the rear wheel keeps the chain from moving so it's easy to add a bit of tension.
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Old 08-26-12, 08:14 PM   #7
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That would be hard to do while the chain is on the bike and if done off the bike it would be tough getting good tension on the chain..
It's easy on the bike. The lower run of chain almost always has at least 12" of unobstructed length to measure and the rear derailleur's spring provides some tension so you get an accurate measurement.

Shifting the chain to the largest chainring and smallest cog will give the longest free run.
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Old 08-26-12, 08:30 PM   #8
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Thanks for the reply's but either way I have no stretch at 6" (will test at 12") is this normal for 3,000 miles ?? do they tend to stretch all at once ??
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Old 08-26-12, 08:30 PM   #9
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what are you getting for miles out of your chains?
I get 800-1000 on a tandem, maybe 1200-1400 on a single road bike.

Mostly run SRAM chains, on mostly flatter terrain, at ~80 cadence, and not huge power.
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Old 08-26-12, 09:08 PM   #10
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You are doing something wrong. Unless you weigh 110 lbs, ride entirely on the level, and spin very easy, you should have chain wear. You're at the point most people either have already switched or need to soon.
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Old 08-26-12, 09:28 PM   #11
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There's no magic number for chain wear. I know people that can't get 2,000 miles, and others that get 12,000. There are simply too many variables, and since I make chain lube, I'd love to say lube is the biggest factor, but it isn't.

The biggest factor is the tension the chain typically runs at, and all things being equal that's related to power. Strong riders riding at good speed or in hilly terrain expend more power, so their chains are under higher tension. The differences are very large; riding on level ground at 15mph uses more than twice the power than riding at 10mph, at 20mph it's 4x, at 25mph it's 6s. Then factor the effects of hill climbing, especially climbing at decent speed and you can see that some people will get vastly shorter chain life than others.

Other variables include sprocket choices, rain, dirt, lube frequency, lube quality, cross chaining and so on.

Instead of fretting that you're not seeing enough wear at 3,000 miles you should instead be celebrating your good fortune.
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Old 08-27-12, 05:56 AM   #12
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You are doing something wrong. Unless you weigh 110 lbs, ride entirely on the level, and spin very easy, you should have chain wear. You're at the point most people either have already switched or need to soon.
I weigh 173, do avg. speeds of 19.5-20.5 solo and 22-23 in groups, do as many hills as I can find and a few training races. I do clean my chain often , try not to cross chain and lighten up on my pedal stroke when changing gears on inclines ... I am surprised but I guess I should be happy.
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Old 08-27-12, 06:10 AM   #13
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Since you seem confident in your measurements, be happy then. The worse thing that happens is you just replace the cassette sooner than expected.
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Old 08-27-12, 06:12 AM   #14
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I have 3650 miles on my current 10 speed chain and it measures less than 1/32" wear over 12", carefully measured with a steel machinist's rule. I'm gonna replace it at 1/32" wear.

I keep the chain well lubed with wet lube and it's seen very little riding in the rain.

Chain checkers that measure between roller to roller are mainly measuring roller wear. Measuring the chain length with a ruler measures only pin/bushing wear.

(note: Bushings are not separate parts but are formed from the inner plates on these chains)
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Old 08-27-12, 06:24 AM   #15
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6 inches is too short a length to use with a rule, even a precision machinist's rule. Use a 12" machinist's rule and place one end of the edge of a pin. The pin at the other end will be completely covered when the chain is new. If the pin that was covered becomes exposed, close to half it's diameter, you've reached .5% elongation.

I've seen a recent wear test that showed less elongation from the latest Shimano chains. Campy chains wear the same way - very little elongation, even after 5-6,000 miles. The problem there is even though there is not much change in pitch, the chain is still shot, with large amounts of roller wear and side clearance that may be twice that of a new chain. If it's not replaced, your second new chain on that cassette may skip on some of the most-worn cogs, regardless of how small the elongation.

Last edited by DaveSSS; 08-27-12 at 06:28 AM.
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Old 08-27-12, 01:15 PM   #16
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The cassette has 4,600 miles / chain 3,000... One other difference could be is most of this chain (all but 266 miles ) was done with Ultergra DI2 components
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Old 08-27-12, 01:23 PM   #17
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A go/no-go chain checker tool, was made more accurate by KMC,
by making a Digital micrometer chain wear measuring tool.

since the OP likes the Di2, then why not make the chain wear test tool
electronic too.
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Old 08-27-12, 01:30 PM   #18
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A go/no-go chain checker tool, was made more accurate by KMC,
by making a Digital micrometer chain wear measuring tool.

since the OP likes the Di2, then why not make the chain wear test tool
electronic too.
A flawed measuring technique is not corrected by making it digital.
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Old 08-27-12, 01:34 PM   #19
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I've seen a recent wear test that showed less elongation from the latest Shimano chains. Campy chains wear the same way - very little elongation, even after 5-6,000 miles. The problem there is even though there is not much change in pitch, the chain is still shot, with large amounts of roller wear and side clearance that may be twice that of a new chain. If it's not replaced, your second new chain on that cassette may skip on some of the most-worn cogs, regardless of how small the elongation.
Hey Dave, I've seen from a couple of posts that you are in the "roller wear matters" camp, and I'm trying to wrap my head around it. If all of the rollers are wearing equally and the chain isn't elongating, how can the "leading" rollers ride up and wear the sprocket teeth?

Thanks.
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Old 08-27-12, 01:48 PM   #20
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FWIW, I have always observed the lowest rate of chain wear (actual elongation) with Shimano chain.
There were many times where I thought I had timed an appropriate point to finally replace a Shimano chain, but the actual measurement kept pushing that time further along.
Credit their excellent metallurgy.
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Old 08-27-12, 02:22 PM   #21
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Read and learn grasshopper. http://draco.nac.uci.edu/rbfaq/FAQ/8d.2.html
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Old 08-27-12, 02:34 PM   #22
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Originally Posted by ducati hyp View Post
Hi, I have a parks chain checker and my chain still doesn't indicate it needs changing (.75) BUT I'm not about to trust that tool , so I measure 12 pins with a steel ruler and see if there is 1/16" stretch and from pin center to 12 pins over and i'm at the center of that pin (6" ) this is after 3000 miles . Is it possible to have almost no stretch after 3K miles ?? Yes I did check in a few spots..
BTW my chain is a shimano 6700
One ? is when new is 12 pins center to center 6" even ??
Also what are you getting for miles out of your chains ?
So you've verified that your Park Tool chain checker works. Chains are relatively cheap. If you are worried about it - change out the chain. Personally, I use the Park tool for measuring chain wear and I am satisfied with the result. Al
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Old 08-27-12, 02:46 PM   #23
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A go/no-go chain checker tool, was made more accurate by KMC,
by making a Digital micrometer chain wear measuring tool.

since the OP likes the Di2, then why not make the chain wear test tool
electronic too.
Nope. The KMC tool still measures between rollers which makes it inaccurate.

The Shimano TL-CN40 with no markings and TL-CN41 with instruction sticker but no scale are accurate.

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Old 08-27-12, 02:47 PM   #24
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'Stretch' is the sum total of accumulated wear,
teeth pull on the rollers, the wear is mostly of the half bushings,
part of the inner link plates, of 'bushingless' chains

and then take more samples.
well, the 8 speed chains are like 1/4 the cost of 10 speed ones ..

I waited till the Drive train, just felt weird, after 6 months of commuting,
fit a new chain and I flipped the Rohloff cog over..

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Old 08-27-12, 02:55 PM   #25
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Park chain checkers (unlike using a ruler) will work very differently on different brands and models of chain.

It's a poorly-designed device with no redeeming value beyond helping to sell chains to riders who don't need a new chain.

I'm all for supporting the LBS, but the Park chain checker (unlike Shimano's compensated chain-wear tool) is near-useless imo.
It measures chain wear, but half of what it measures doesn't count since it adds in the roller freeplay which doesn't contribute to the pitch or elongation measurement.
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