Author Topic: So what's going on with this chain?  (Read 1800 times)

So what's going on with this chain?
« on: 24 November, 2011, 03:12:37 pm »
I've just cleaned my goldie lookin' chain and have noticed that the Titanium Nitride plating has worn significantly more on one side of the chain than it has on the other.
Not sure how clear this'll be on the posted pics:

Exhibit A:


Exhibit B:


Now, why would that be?
I've noticed for a while when the chain is on the bike, one side (the nearside) gets blacker with gunge much more quickly than the offside / drivetrain side, which stays shiny and goldie lookin'.
Unfortunately I can't relate that to the above, other than by guesswork ???

Gears are operating just as Shimano intended.

Any ideas?

Rhys W

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Re: So what's going on with this chain?
« Reply #1 on: 24 November, 2011, 03:19:15 pm »
I've noticed that on the same model of chain. The only thing I can think of is wear as the chain is pushed up to a larger sprocket. The inner side will rub against the larger sprocket momentarily. Dropping down the other way (onto a smaller sprocket), there's nothing in the way.

Kim

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Re: So what's going on with this chain?
« Reply #2 on: 24 November, 2011, 03:20:50 pm »
Front mech?  Lots more scraping involved in changing up than down...

Re: So what's going on with this chain?
« Reply #3 on: 24 November, 2011, 03:22:28 pm »
They seem to do this when used with compact chainsets.  I think the worse chainlines you inevtiably employ rub the chain against the next sprocket or front mech more than with a conventional double or triple system.  I think.

zigzag

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Re: So what's going on with this chain?
« Reply #4 on: 24 November, 2011, 03:46:22 pm »
i'd agree with Rhys W, that chain rubs half a turn or so at the bigger sprocket's side before it's picked up when downshifting. shifting up the chain just jumps off to the smaller sprocket with no rub.

Rhys W

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Re: So what's going on with this chain?
« Reply #5 on: 24 November, 2011, 03:57:04 pm »
I've noticed this, and I don't have a compact.

As you shift from inner chainring to outer, the front mech pulls the chain up and pushes it to the right, so yes, maybe you'd have some rubbing of the inner plate against the inner side of the chain. However, shifting down to the inner ring, the outer plate would push against the outer side of the chain. These two effects would cancel out almost perfectly.

Changing at the rear is more to do with the chain following the new position of the jockey wheels - there's no cage pushing the sides of the chain. Plus you probably shift 5-10 times more frequently at the back than at the front.

clarion

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Re: So what's going on with this chain?
« Reply #6 on: 24 November, 2011, 04:31:05 pm »
Yup.  Front changer seems to be the most likely culprit.

Unless it's malicious leprechauns armed with Brillo pads.
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Kim

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Re: So what's going on with this chain?
« Reply #7 on: 24 November, 2011, 04:34:22 pm »
As you shift from inner chainring to outer, the front mech pulls the chain up and pushes it to the right, so yes, maybe you'd have some rubbing of the inner plate against the inner side of the chain. However, shifting down to the inner ring, the outer plate would push against the outer side of the chain. These two effects would cancel out almost perfectly.

I dispute that.  Anecdotally, less force (and, depending on shifter, time) is required to derail the chain to the smaller ring than to hold it far enough over to catch on the bigger one.

Biggsy

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Re: So what's going on with this chain?
« Reply #8 on: 24 November, 2011, 04:38:54 pm »
Front mechs usually have smooth rounded stainless steel edges and surfaces that are gentle on the chain, so I'm doubtful.

Not a real problem anyway.  The chain will wear out from the inside before corrosion eats the plates.
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frankly frankie

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Re: So what's going on with this chain?
« Reply #9 on: 24 November, 2011, 06:15:41 pm »
As you shift from inner chainring to outer, the front mech pulls the chain up and pushes it to the right, so yes, maybe you'd have some rubbing of the inner plate against the inner side of the chain. However, shifting down to the inner ring, the outer plate would push against the outer side of the chain. These two effects would cancel out almost perfectly.

But it's the rubbing against the larger chainwheel as you change up - not the front mech.  And that doesn't cancel out going the other way.

Though actually I'm with Tewdric on this one.  Generally.  Depends on how long the chainstays are, but with shortish ones, it's very difficult to get a chainline where the smallest rear sprocket doesn't cause rubbing.
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Rhys W

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Re: So what's going on with this chain?
« Reply #10 on: 24 November, 2011, 08:20:57 pm »
As you shift from inner chainring to outer, the front mech pulls the chain up and pushes it to the right, so yes, maybe you'd have some rubbing of the inner plate against the inner side of the chain. However, shifting down to the inner ring, the outer plate would push against the outer side of the chain. These two effects would cancel out almost perfectly.

But it's the rubbing against the larger chainwheel as you change up - not the front mech.  And that doesn't cancel out going the other way.


That's rubbing the outer face of the chain. What I have experienced (and the OP I think) is wearing of the plating on the inside face of the chain.

Re: So what's going on with this chain?
« Reply #11 on: 24 November, 2011, 09:56:04 pm »
I'm sold on the idea that it would be the chain rubbing on the next sprocket up at the rear, probably during shifting, but maybe during normal operation as well.
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Re: So what's going on with this chain?
« Reply #12 on: 25 November, 2011, 07:35:08 am »
Thanks all, for your considered collective responses.

As Biggsy says it's not really a problem - more to do with curiosity on my part - particularly given the marked contrast of filth on the inner side of the chain when on the bike, while the outer remains sparkly.

For the record, the bike has a triple chainset, and very short chainstays.

I'm erring towards Rhys W's suggestion of the rub on the 'next up' sprocket being the cause of wear, and probably also the accumulation of gunk.
By comparison, it looks like the surfaces of the front cage (both inner and outer) are far more smooth and benign. For instance, they don't have the break in surface, as do the sprockets on the rear, thanks to the ramps.

As an aside, how do ramps work? Do the ramps on the next-desired-change-up-sprocket 'grab' the chain to assist it's path onto the larger sprocket? Or are they there to make it easier for the chain to 'leave' the smaller sprocket on it's way to the larger one?
If it's the former, why does the smallest sprocket have ramps? Conversely, if it's the latter - why the need for ramps on the largest sprocket? Or am I totally missing something about how ramps work.

Front mechs usually have smooth rounded stainless steel edges and surfaces that are gentle on the chain......
Not stainless. Of that I'm fairly certain. The cage will snatch a neodymium magnet to it like a rude snatchy thing. Most stainless in this application is austenitic and only very faintly ferromagnetic. Martensitic stainless, whilst magnetic would, I suspect, be way too brittle to be used for a cage.

... Anecdotally, less force (and, depending on shifter, time) is required to derail the chain to the smaller ring than to hold it far enough over to catch on the bigger one.
Is that not more because while you're changing from small to large you are working against the force of the spring? Irrespective of whether we're talking about front or rear changing.

All this leaves me with something of a dilemma when it comes to re-fitting the chain:
Do I reap the benefits of the lower coefficient of friction of Titanium Nitride plating, and fit the blingy side inwards where it appears to rub on sprockets as it changes up?
Or do I leave the blingy side facing outwards so the drive train looks good in photos?  ;)

Re: So what's going on with this chain?
« Reply #13 on: 25 November, 2011, 08:21:08 am »
All this leaves me with something of a dilemma when it comes to re-fitting the chain:
Do I reap the benefits of the lower coefficient of friction of Titanium Nitride plating, and fit the blingy side inwards where it appears to rub on sprockets as it changes up?
Or do I leave the blingy side facing outwards so the drive train looks good in photos?  ;)

You missed an option there due to being a cheapskate - new chain - this allows you to reap both benefits and avoids the crushing embarrassment of shoddy, or naff, worn outer blinginess. But don't listen to anyone that tries to tell you that a gold chain, in any state of wear, is naff blinginess  ;D
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Biggsy

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Re: So what's going on with this chain?
« Reply #14 on: 25 November, 2011, 09:24:29 am »
I reckon ramps are to assist climbing up to the larger sprocket, and any shortened teeth assist leaving the smaller sprocket.  Sometimes some of the teeth are slightly twisted as well.  I'm not sure which direction they help with - perhaps both.

Same with chainrings, sometimes with the additions of pins - that you can watch actually picking up the chain when you pedal slowly.

All this is designed with the help of sophisticated computer programs these days, that simulate chain behaviour.  This is where some of your money goes when you buy Shimano and Campagnolo cassettes and rings rather than plain alternatives.

Thanks for the info about the cage probably not being stainless steel.
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