Author Topic: Should I replace Chain.  (Read 729 times)

Brush2805

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Should I replace Chain.
« on: July 23, 2018, 02:42:42 PM »
My Raven is just over three years old now.
Over the last three or four years I've often read this forums and found them very informative.
I've now reached the point where I can't tension the chain sufficiently using the EBB.
So what would you guys normally do at this point?
Is it best to fit a new chain or remove a link from the existing chain?

mickeg

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Re: Should I replace Chain.
« Reply #1 on: July 23, 2018, 04:42:21 PM »
I measure my chains to determine when they exceed 0.75 percent elongation.  And replace at that time.  Some people use their chains until it reaches 1 percent elongation.  There is no specific right amount of wear to use.  A few years ago I bought a bunch of chains at a very significant discount, thus I would rather wear out more chains and fewer chainrings & sprockets.

I live in USA where it is easy to find long measuring tools calibrated in inches, which is fortunate for me because a chain link is exactly a half inch long.  I use a 48 inch long ruler to measure my chain when it is off of the bike.

You can buy a small chain checking tool, but I find them to often say that a chain needs replacement before they really need replacement.  I use one of those tools to determine if I need to take my chain off of the bike to measure it with the precision I get with my 48 inch long ruler.

Two days ago I adjusted my chain on my Nomad, it was starting to look pretty sloppy the way it hung down.  I used one of those small chain checkers and that said that I had not reached 0.75 percent elongation so I did not bother to take the chain off the bike to measure with more precision.

If you try to measure the chain off of the bike, assuming that you do not have a long measuring tool in inches, you likely will have to measure it in mm and make a conversion to inches to calculate the percent elongation.

I am not familiar with your specific Raven, but if it uses the same bottom bracket eccentric that the Nomad uses, I think you can remove two links to make the chain work.  (Perhaps someone else will comment on that?)

Since everybody uses different chainring sizes, some use different number of teeth on the sprocket, different frames have different chain stays, etc., what works on my bike might not work on yours.  I reach the amount of chain elongation that makes it due for replacement before I have to remove any links.  That might not be the case for your bike.

Some people refer to elongation as chain stretch and I sometimes use the word stretch too.  But technically nothing is stretching, you are measuring the increased wear within the chain parts and how much longer the chain is because of that wear.

geocycle

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Re: Should I replace Chain.
« Reply #2 on: July 23, 2018, 05:37:09 PM »

I've now reached the point where I can't tension the chain sufficiently using the EBB.

Is it best to fit a new chain or remove a link from the existing chain?

Mickeg gives you the correct way.  However, I have always used the point where I can no longer tension the chain as a useful signal it should be replaced.  There are other variables at play eg frame size and gear ratios but for me this is a useful indication.  I've never had much luck with removing a link as it usually ends with a chain that is far too tight, instead you'd need a half link.  I tend to find a chain does about 2 years or 6000 miles for me.  I do try and run two chains in parallel so they wear at the same time as the sprockets and chain rings. 
 

martinf

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Re: Should I replace Chain.
« Reply #3 on: July 23, 2018, 08:10:03 PM »
With hub gears you can run the chain well past the 1% wear point, but doing this wears out (one side of) the sprocket and chainring. And very worn chains are more prone to snapping (done this). So IMO best to replace the chain.

If the new chain skips, reverse the sprocket. Chainring is probably still OK, but you can probably reverse it as well if needs be.


Matt2matt2002

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Re: Should I replace Chain.
« Reply #4 on: July 25, 2018, 08:16:15 PM »
Can I tag this question on here?
It there anything to be said for flipping.or reversing the chain when a certain degree of wear had taken place?
Or is a worn chain just that, no matter what 'way' it is used?
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mickeg

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Re: Should I replace Chain.
« Reply #5 on: July 26, 2018, 12:51:04 AM »
Can I tag this question on here?
It there anything to be said for flipping.or reversing the chain when a certain degree of wear had taken place?
Or is a worn chain just that, no matter what 'way' it is used?

A worn chain is a worn chain.  Sorry.

Flipping the sprocket or chainring is different, the teeth are mostly worn on only one side and by flipping them you get to wear the other almost unworn side of the teeth.


Matt2matt2002

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Re: Should I replace Chain.
« Reply #6 on: July 26, 2018, 05:29:07 PM »
Thanks Mick
I'm sure you are correct but I definitely read somewhere about the ' benefits' of Flippin a chain.
But then you can read most things somewhere on the Webb.!!
Never drink and drive. You may hit a bump  and spill your drink

Andre Jute

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Re: Should I replace Chain.
« Reply #7 on: July 27, 2018, 01:05:08 AM »
... I definitely read somewhere about the ' benefits' of Flippin a chain.

I don't think anyone is pulling your chain, Matt.

The wear causing elongation on the chain, often called "stretch", is between the roller and its bearings under it. There's one roller and set of bearings at each end of each link. The inside of the roller, being a free-spinning agent, will be evenly worn. The bearings, which are solid, will be worn only or mostly on the side in contact with the chainring and sprocket. Therefore, if you undo the chain and flip it so that the other side (which used to be the top and bottom outside runs) is in contact with the teeth, a new bearing wear surface will be presented to the roller. Note the "only or mostly" -- I think it is "mostly", implying that the extra wear you get will be less than on the first run of the chain. I think it is likely to be much less, so the candle may not be worth the effort, but then I'd rather preserve my expensive chainring and sprocket than maximize chain life at their expense. Since you should still replace the chain when total elongation reaches .75 on your gauge, to get full value from the extra work you should swap the chain top to bottom (rather than front for rear) at about half its increased full life expectancy.

If you try it, let us know the result.

mickeg

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Re: Should I replace Chain.
« Reply #8 on: July 27, 2018, 03:22:29 AM »
...
The wear causing elongation on the chain, often called "stretch", is between the roller and its bearings under it. There's one roller and set of bearings at each end of each link. The inside of the roller, being a free-spinning agent, will be evenly worn. The bearings, which are solid, will be worn only or mostly on the side in contact with the chainring and sprocket. Therefore, if you undo the chain and flip it so that the other side (which used to be the top and bottom outside runs) is in contact with the teeth, a new bearing wear surface will be presented to the roller. ...

I do not agree, but it won't hurt anything if you flip it.

I think Sheldon had it right.  The pin and the inner plates were where most of the wear is.  And that is why the chain gets longer.  The wear occurs as the chain wraps and unwraps around the sprockets and chainrings, the pins rub against the inner plates in the process during wrapping and unwrapping.  And, the tension of the chain can be quite high which puts a lot of force on those moving parts. 
https://www.sheldonbrown.com/chain-wear.html

Andre Jute

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Re: Should I replace Chain.
« Reply #9 on: July 27, 2018, 06:53:11 AM »
This is a very minor disagreement about a most likely very modest gain in chain life, even if I'm right. But we can define the likely gain a bit further:

The roller, as its name implies, in the end is likely to be worn the same amount all round, so flipping the chain will not necessarily affect its contribution to chain life except marginally, as I will explain below.

But the bearings in a never-flipped chain are worn on three sides only, because that is where they bear load as chain ramps up and off the teeth on the gears. On the outside of the chain (horizontal flat surface pointing at the sky and the ground) the bearings bear no load and wear only in relation to the dirt that clumsy oiling (on both sides of the rollers, so creating an air lock for the dirt inside) or no oiling has left in between the roller and the bearings.

So the marginal gain to "standard practice life" (not flipping the chain) that flipping the chain will add is a variable feast depending on when the chain is flipped. In any event, it cannot ever be greater than one third of (at a first approximation) one half of SPL, because three of the four 90 degree sides of the bearings are already worn when the chain is flipped, and two of them will wear further even as the fourth side wears down. This identifies the maximum theoretical gain with one flip as 16.666 percent. I'll explain below why the gain could be much smaller.

One can however escape this limiting condition by regularly flipping the chain, so that all the bearings wear down smoothly, in which case a gain of 33.333 percent is the theoretical  maximum; see below about complicating factors leading to a likely much smaller gain. Explanation follows:

Remember that chain wear is measured cumulatively on the edges of the bearings aligned vertically, whereas we are now talking about slowing total chain wear by bringing in a second horizontal edge, where previously only one horizontal side of the bearing was in full use.

So what we have to determine is how much bringing the second horizontal side into play will slow down wear on the two vertical bearing sides. It seems to me that some slowing will occur because, from the roller's viewpoint, the bearing is now ovoid rather than asymmetrically round, and thus, until the roller wears down the new surface of the bearing presented to load, the sides over which we will measure elongation will wear somewhat slower.

Taking a wild guess <tm>, I'd say that with one flip of the chain during its life, the gain could be between 3 and 5 percent, and with many flips possibly double that. That is also a hint that any experiment had better be done by a high-miler and quite carefully controlled because we're working with relatively small fractions of total mileage.

Unfortunately, that's not all that cerebration leads us to:

It may also be the case that flipping the chain, especially flipping it only once when the bearings are half worn on three sides, disturbs the roller which previously rotated in harmony with the incremental wear on the bearings, or that the new bearing surface even gouges the roller, in which case the longevity gain on the chain will be negative (a euphemism for "fewer miles per chain").

Brush2805

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Re: Should I replace Chain.
« Reply #10 on: July 27, 2018, 11:32:43 AM »
I looked at the Thorn supplied manual for my Raven. The manual does suggest to remove a link rather than replace the chain.
I did measure my chain and as youd expect its well worn.
So I guess Thorn are suggesting that you really run the same chain until sprockets and chain rings are so worn that the chain starts skipping.
Then I guess you flip them over and start again?
Surely this is rather the opposite to the widely held view that we replace chains to save wear on other components.
I wonder which is most cost effective in the long term on a Rholoff hub equipped bike?
People who own expensive derailleur bikes seem very keen on trying to avoid wear on expensive cassettes so change chains regularly.

Matt2matt2002

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Re: Should I replace Chain.
« Reply #11 on: July 27, 2018, 04:00:45 PM »
Brush....
I'm a newbie on chain info but I'd be surprised if Thorn imply or suggest running a chain until the sprockets are ruined.

Chains are a lot cheaper than sprockets and easier to change. Although cost is not always the most important factor

Flippin chains!
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mickeg

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Re: Should I replace Chain.
« Reply #12 on: July 27, 2018, 05:38:53 PM »
Ok, you have convinced me to switch to belt drive.

Just joking.

The cost effective solution I am most sure will depend on the quality of the chains, how well maintained (choice of lube, frequency of application, how often chain tension adjusted, ---), cost of chains, diameter of chainring(s), chainring material and cost, conditions (wet or dry, dusty or not, ...), the list could go on and on.

And the cost factor certainly would also include who does the work, the bike owner or a bike shop that is paid to do the work.

The only constant in this is the sprocket since everyone uses a Rohloff sprocket.  Oops, that is not even constant, I use a 16T sprocket as I suspect most Rohloff riders that do not ride Thorns, but Thorn riders predominantly use a 17T sprocket if they got their Rohloff from SJS.  (I bought my Rohloff from someone other than SJS, thus I use the standard Rohloff sprocket of 16T on my Nomad.) 

Thus, I think there is no single most cost effective solution.

julk

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Re: Should I replace Chain.
« Reply #13 on: July 27, 2018, 05:43:19 PM »
I my experience using a chainglider is the most cost effective solution on a Rohloff geared bike.
It will keep your chain, sprocket and chainwheel in good condition for a very long time.
Julian.

Matt2matt2002

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Re: Should I replace Chain.
« Reply #14 on: July 27, 2018, 07:33:30 PM »
Me too.
I'll soon be presenting my Chainglider experience.
I've had it in for 3+ years and 3 long tours.
Never drink and drive. You may hit a bump  and spill your drink