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Discussion Starter #1 (Edited)
And how much is OK?

I took my very Cow Mt. dusty chain and hung it so it was straight up and down. I then took a tape measure and aligned the 9" mark with a rivet near the top and duct taped it together. (Pictures rotated horizontal to make them easy to read.) On a 4XX chain the rivets are exactly 1/2" apart.

Chain1.jpg

I then looked 18" down the tape measure (at the 27"mark) and found the rivets and the half inch marks no longer aligned. The rivet that belonged at the 27" mark was now at the 27 1/8" spot.

Chain2.jpg

Looking 36" down the tape (at the 45" mark) the rivet was 1/4" past where it belonged.

Chain3.jpg

So how much stretch is OK?

A little internet research says .006" per link (and I guess they mean for each rivet) is the max. There are 73 rivets in 36 inches. 73 X .006 = .438" = 7/16" which means I can use this chain until it stretches another 3/16 inches per 36" of chain.

There are approx. 24,000 miles on the chain now. By my calculations it should last until 42,000 miles -- which is a figure I find very hard to believe.
 

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And how much is OK?

There are approx. 24,000 miles on the chain now. By my calculations it should last until 42,000 miles -- which is a figure I find very hard to believe.
Excellent info. I remember seeing the way to measure the stretch of the Yamaha chain, but can't remember where.

A guy on the Triumph forum got a documented 40,000 miles on a Bonneville x-ring chain. I can get about 20,000 miles on an o-ring chain before I feel the need to change it, even if it looks OK.

What comes to mind is that the wear may not be linear. As the chain wears, it may wear more quickly as the tolerances increase.

jb
 

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Technically, a chain does not stretch, it wears. The effect of wear on the rollers and rivets is that the chain gets longer. The side plates do not change. The test for excessive wear is to try and lift one link off the rear sprocket at the middle. If you can lift one end of that link to, or beyond, the top of the tooth, the chain is worn beyond a safe amount. This is how chains get thrown, usually at max speed, and it's not a pretty sight.:eek: IMO, trying to see just how many miles you can get out of your chain is NOT worth the risk of it coming off at 60 on a highway!

42,000 miles on a dirt bike chain? Not HARD to believe, IMPOSSIBLE to believe! My guess is that by the above technique your chain is ready for replacement, and so are the sprockets. (Both chain wear and sprocket wear contribute to the above test.)

And yes, jbfla is right, the wear is often not linear, so perform the test in several places.
 

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Discussion Starter #9
I have been told that a stretched chain causes the rollers to ride higher on the teeth causing them to bend over making the sprocket look like a tsunami warning sign.

When I installed this chain I also installed new sprockets. The front, rear, and chain have been together for the 24K or so miles.

On the front sprocket the teeth are worn but standing straight up. (Excuse the flash rust -- I just washed the bike.)

P5051316a.jpg

The rear sprocket looks good to me.

P5051314.JPG

And the pull test. I still think it is less than 1/2 a tooth.

P5061323.JPG P5061321.JPG
 

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.....

When I installed this chain I also installed new sprockets. The front, rear, and chain have been together for the 24K or so miles.
Is that an O-ring chain? If not, that's really good mileage! You must clean and lube it often. (Just because you have an O-ring chain doesn't mean you shouldn't clean and lube it often.):)
 

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Discussion Starter #11
Is that an O-ring chain? If not, that's really good mileage! You must clean and lube it often.
It is a regular chain. Not o-ring. And I do clean and oil it a lot. I have an o-ring chain on the shelf waiting for this one to wear out but I am trying to see how long I can make this one last.
 

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Measuring chain stretch, another take:

Just replaced an oring chain and rear sprocket that were seriously toast after less than 1000 miles of mainly abrasive mud and sand and water, and ran offset on a dual sprocket. Busted out the micrometer and heres what I found:

New chain

Interior dimension=4.42mm
Bar dimension=4.41mm

Worn Chain

Interior dimension
lengthwise=4.63mm
Transverse interior=4.47mm
Bar dimension (varies 4.26-4.19mm)

At this point the chain laid flat on the floor can be bent around in a circle of about a 2 foot diameter. Chain still performing well but worn way beyond what it should have been. When its stretched this much it seems like its causing an inordinate amount of sprocket wear.
 

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Discussion Starter #15
WOW! Only 1,000 miles. My guess is your front sprocket needs replacing too. So much for the argument o-ring chains are maintenance free. They must be cleaned and lubed too. A thousand miles isn't very far.

I have worked out for myself a technique for measuring chain stretch.

1) Remove chain guard. Place TW in first gear and push backwards until tension on chain, I then roll the bike up on the kickstand and place 4X4 in front of rear tire so tire is about 2" off ground. This keeps the upper chain very taut.

P1230001.JPG

2) Place ruler on chain. I use the 1" mark on the tape and have the roller touch the the tape exactly at the 1" mark.

P1220006.JPG

3) Then I look at the 19" mark ( 18" of measurement) and read how much the chain has stretch. Zero stretch and the roller will be exactly on the 19" line. As you can see the roller is half way between the 19 1/8 " and 19 3/16 ", or approximately 5/32" of stretch. ( Due to parallax it looks like 19 1/8" but it is really 19 5/32 ". To those of metric up bringing I wish I had a metric measuring stick long enough and I would measure it again.)

P1220008.JPG

5/32 = about .16 " 37 pins in 18 inches so this works out to .004" stretch per pin. According to one source on the internet that I quoted earlier .006" is allowed so theoretically I am still safe. However, I am getting nervous. I have new sprockets and a new o-ring chain ready to go and for peace of mind they will soon be installed.

BTW, 25,500 to 26,000 miles on this chain and set of sprockets. Tony
 
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