Chain wear

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Mick F
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Re: Chain wear

Postby Mick F » 16 Jun 2011, 8:38am

Mick F wrote:There is ZERO stretch that I can see on it when measured with my 39" rule.

Sorry, I've just re-measured my Chain A.
It's got 1/16th of an inch stretched over the 39" and there's no sign of an error in 12".

My chain checker won't go in at all.
Mick F. Cornwall

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Re: Chain wear

Postby Cyclenut » 16 Jun 2011, 9:38am

Dan wrote:Niggle, you are (nearly) correct, the Rohloff Caliber 2 measures stretch at 0.075 and 0.1 mm PER LINK (according to the instructions), not 0.075% and 0.1% as I mistakenly thought. So I was out by a factor of 1/25.4=0.039

Taking 1 link to be 1 inch (25.4mm) of chain the Rohloff chain checker calibrations of 0.075mm and 0.1mm per link translate to 0.075/25.4x100=0.30% and 0.1/25.4x100=0.39%.

Let's get this straight once and for all (some hope :( ): We don't describe an inner link or an outer link as an inner or outer half-link, and the label on a new chain speaks of it having a hundred and something links, so I think it's safe to assume that the cycle industry universally regards one link as being that fraction of a chain measuring half an inch i.e. 12.7mm in length. So the Rohloff tool callibrations of 0.075mm and 0.1mm correspond with wear percentages of 0.6% and 0.8% respectively.

Direct measurement of my old centaur chain against the new KMC showed it had stretched by 5mm over the length of the whole chain. This gives 5/1370mm = 0.36%.

Interesting that this is less than the 0.39 according to the chain checker. Presumably 0.36% is the true figure (unless older chains are more elastic and have to be measured under tension) and the chain checker produces a reading of 0.39% because increased play in the rollers exaggerates the stretch, as Niggle pointed out in an earlier post.

Quite right and then some, with bells on, since the Rohloff chain checker actually indicated 0.8%, a massive over-reading of the wear in this chain, due to the way this tool measures two doses of roller play/wear, in addition to the few doses of pin wear that are spanned in its very short length.

I once measured a brand new but very cheap and nasty chain with my Rohloff checker, according to which it was completely worn out already at 0.8% elongation, though when pulled out against a steel tape its 118 links measured precisely 59 inches. But this chain had very sloppy rollers. Q.E.D. Niggle!

Before I lost it, I improved my Rohloff chain checker by tethering a wedge of metal to it, that I would insert into the link before the section of chain I was measuring. This wedge shoved the "zero" roller forward, in the same direction as the roller at the other end of the measuring section would be shoved by the checker. This took the spurious factor of roller play/wear completely out of the equation, so the tool now measured purely pin wear, like it was supposed to. After that its indications of wear became much more consistent with measurements of whole chains after removal.

In order to be sure that a new chain will run on the old cassette, I've found it's necessary to scrap the old one at about 0.5% actual wear. By 1% it's too late, some sprockets will jump. But if you're going by an un-improved chain checker that adds in two doses of roller play, it's possible that you have only 0.5% actual wear when the checker says 1%.

Anyway the chain has stretched enough to have worn my 11 tooth sprocket badly enough that a new chain jumps on it.


That's bad luck, given that you had less than 0.5% actual wear and a good illustration of the truism that YMMV (your mileage may vary)! Smaller sprockets will be more prone to wear and jumping from the same amount of use with a worn chain. But touring cyclists like me have very little use for the 11T top (or even the 13T next to it) that comes with the 34T we really want at the other end! So they're usually still in excellent nick regardless. When I leave a chain on too long, it's the middle-to-big ones that jump. I guess I should keep the pristine tiddlers from those cassettes and trade them with top gear mashers like you! :wink:
Chris Juden (at home and not asleep)

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Re: Chain wear

Postby Ayesha » 16 Jun 2011, 9:49am

Stand the bike against a wall with the chainset facing you.

Stoop down with your 12" rule and put some pressure on the pedal to pull th etop stretch of chain tight.

Place the 12" rule so it measures over 10 links ( nominal 10" ). Left edge if rivet to left edge of rivet.

10 1/16" is 0.66% worn. Renew chain now if you have the spare cash.


What a worn / elongated chain does....

Rides up on the chainring teeth and then suddenly beds into the profile when pressure is applied. It feels like the Bottom bracket is loose. It makes an elongation of the chainring profile. A 'hooked' chainring.

Does the same to the sprocket.


I find a Sachs silver lasts 4000 miles. I check every 1000 miles, so its an annual renewal on two of my bikes.

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Re: Chain wear

Postby Edwards » 16 Jun 2011, 9:49am

Chris if I may ask you a question. When I use my Park toot chain checker I tension the chain by putting the front brake on and pressing the pedal down. Then I see if the tool will just slot in not pushing it down, more resting on the chain.
Will this give a more or less accurate indication of wear when only using the tool?
Keith Edwards
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Re: Chain wear

Postby Cyclenut » 16 Jun 2011, 10:04am

Edwards wrote:Chris if I may ask you a question. When I use my Park toot chain checker I tension the chain by putting the front brake on and pressing the pedal down. Then I see if the tool will just slot in not pushing it down, more resting on the chain.
Will this give a more or less accurate indication of wear when only using the tool?

Makes no difference. The tool will tension the bit of chain it's measuring well enough by itself, and it'll add in those two spurious doses of roller play regardless.

The only way to cancel roller play is to give a wedgie to one of the links adjacent to the measuring section.

The Park tool is a bit longer than the Rohloff though, so the roller play is slightly more diluted (but not much). Also the fingers on the Park Tool are square, making it a simple GO or NO-GO gauge, whereas the fingers on the Rohloff are slightly tapering, so you can estimate in-between amounts of wear by how far in they go.
Chris Juden (at home and not asleep)

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Mick F
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Re: Chain wear

Postby Mick F » 21 Jun 2011, 2:31pm

Mick F wrote:
LANDSURFER74 wrote:Take each end of chain and try to form a circle.
If a half circle is achived, bin chain.

Why?

Why bin a chain when it gets like this? There is ZERO stretch that I can see on it when measured with my 39" rule.


I have a new Campag Chorus chain now (they call it Centaur, but it's the old Chorus) and cut it to length. It will now be referred to as Chain C.
A and B will take a rest until C has done 4,000 or so miles.

I arranged them all on the kitchen table and bent them in an attempt to form a circle. The ruler shows beyond where the half circle is. As you can see, A and B are similar, but a brand new chain isn't far behind. Without measuring precisely, I reckon the brand new chain is just about a half circle. No doubt if I held it, I could form a half circle.

I fail to see why this is a good test of chain wear.
Chain Curves.jpg
Mick F. Cornwall

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meic
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Re: Chain wear

Postby meic » 21 Jun 2011, 2:44pm

It looks like a good test of chain wear to me as most of my chains get retired before their linear growth is the problem, they get retired because they start snaking around the front changer and refusing to swap chainrings.

The only point is that you dont wait until the rather arbitrarily chosen limit of completing a circle.

On the other hand the test is superfluous because the fact that it will not change gear any more lets me know that my chain is too worn to change gear any more. :wink:

It is only the linear growth that you have to measure as that is what wears out your chainrings and cassettes prematurely.
Yma o Hyd

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Re: Chain wear

Postby cadseen » 21 Jun 2011, 9:35pm

Use a proper Chain gauge and replace chain before it reaches 1% wear.
That way you wont ruin your cassette early.

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Mick F
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Re: Chain wear

Postby Mick F » 21 Jun 2011, 9:39pm

Yes, that's already been discussed.
Chain stretch is a well-known fact for destroying sprockets.

My question is why would one bin a chain if it bends?
Mick F. Cornwall

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Re: Chain wear

Postby reohn2 » 21 Jun 2011, 9:54pm

meic wrote:It looks like a good test of chain wear to me as most of my chains get retired before their linear growth is the problem, they get retired because they start snaking around the front changer and refusing to swap chainrings........


I've never had that problem.
I do find that the change on the rear mech isn't quite as slick when a chain is getting near its wear limit and am pleasently surprised how slick the change really is when the new chain is fitted, but I can't say I've ever noticed anything like you've experienced with the front change.
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meic
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Re: Chain wear

Postby meic » 21 Jun 2011, 11:01pm

It happened on the hard climbs mostly and can be avoided by changing the chainring earlier on before the tension in the chain builds up too much.
Yma o Hyd

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Re: Chain wear

Postby [XAP]Bob » 23 Jun 2011, 12:02am

Mick F wrote:Yes, that's already been discussed.
Chain stretch is a well-known fact for destroying sprockets.

My question is why would one bin a chain if it bends?

Bet mine would make a circle, but then it is quite long...
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Re: Chain wear

Postby Dan » 9 Oct 2011, 3:04pm

Since my June posting that my Campag Centaur 10s chain had stretched 5mm over its 1370mm length (0.36%), and had worn out my 11 tooth sprocket (such that a new KMC chain skipped on it) I put on a new KMC chain (£20) and Centaur block (£60).

After 3 months and approximately 1,200km of road club riding, with regular cleaning and lubrication, I took it off today and it has stretched 3mm over its 1370mm length, that is 0.22%.

Chris your points about the inaccuracy of the Rohloff chain checker, due to "roller play" leading to overestimated wear, and 11t sprockets wearing more quickly are taken.

Mick F, you write
I use two Campag chains and swap them over every 1,000miles or so. Both chains have done over 4,000miles so far with zero stretch on either of them. I expect to get a further 4,000miles yet but I may change them before that.
How do you measure the stretch?

So what to do?
Do I bin my old KMC chain (given that it has stretched 3mm (0.22%) and my previous chain had worn out my 11t sprocket by the time that it reached 5mm (0.36%) stretch), and keep running new chains for 1,200-1500km each? And see how many chains the cassette survives.
Or do I run a couple more new chains for 1,200-1500km each and then rotate the old stretched ones? Before replacing the lot, with the aim of using three chains to one cassette.

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Re: Chain wear

Postby Trigger » 9 Oct 2011, 5:00pm

It seems like you'd be best looking at changing the chain rings if you're spending a lot of time in the 11t cog :?

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Re: Chain wear

Postby reohn2 » 9 Oct 2011, 5:55pm

Dan wrote:So what to do?
Do I bin my old KMC chain (given that it has stretched 3mm (0.22%) and my previous chain had worn out my 11t sprocket by the time that it reached 5mm (0.36%) stretch), and keep running new chains for 1,200-1500km each? And see how many chains the cassette survives.
Or do I run a couple more new chains for 1,200-1500km each and then rotate the old stretched ones? Before replacing the lot, with the aim of using three chains to one cassette.


If you find you're using the 11tooth cog a lot I'd do as Trigger suggests and put bigger chainring(s) on as the more teeth engaged on the chain the less chain wear ie; tandem timing chains and chainrings wear out faster on smaller rings,its the same with small 11tooth cogs on cassettes.
I find I get 2,500 to 2,700 miles out of a rear(not timing) tandem chain(Sram 971) before it reaches 1/8" wear and usually wear out three chains before the cassette is worn out,there is a lot more torque going through a tandem chain than a solo one.
Solo chains usually last 4,500 to 5,000 miles (Sram 971 9speed and 870 7speed) again usually three chains before the cassette is worn out.
I use Shimano HG50 cassettes.
The smallest cog on any cassette I have fitted is 13 or 14 tooth.
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