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Expanded or Worn Chain?

Old 07-26-20, 07:00 AM
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tommyd49
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Expanded or Worn Chain?

Hi everyone

It's been quite a few years since I posted on this forum, so hello again to everyone!

The other day I picked up a steel-framed Raleigh Amazon hardtail. A friend of mine gave it to me - I think someone where he worked had just left it a few years ago, so he picked it up and left it sitting around at his for a while.

One of the main issues is hopefully visible in the two photos I've attached. The rear derailleur seems to be sprung back to its "natural" position, how it would look if disconnected completely from the chain.

The chain is actually on the bottom rear cog and the bottom front cog. Obviously, the rider wouldn't/shouldn't go in to this position much when riding, but I wouldn't expect the rear derailleur to spring back like that when the chain is on. This was the condition I found the bike in.

Shifting to the middle front cog eliminated the problem. It seemed to me that the chain was too slack in the position of the smallest cogs. Maybe the chain is too long - but everything on the bike looks original. I figured the chain might be a bit worn, so I tried the measuring trick - if 12 full links is 12 1/16" or longer, the chain is worn. I only had a 6" ruler to hand, so measured 6 links - which was about 6 1/8". Makes 12 links 12 1/4" - very worn!

It seems strange that the chain could be so worn whilst the cogs all look in good condition.

So, can I ask:
  1. Has anyone seen a chain so worn whilst the cogs are in good condition? Or else has the chain somehow expanded over time, therefore loosing tension?
  2. Does it seem likely that an extra 1/4" or so of slack in the chain would be enough that the rear derailleur would no longer be pulled forward, thereby going back to its "natural" position?
Interested to hear any opinions. Thanks!


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Old 07-26-20, 08:17 AM
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WGB 
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Possibly a PO replaced the cassette or even wheel and cassette but not chain?
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Old 07-26-20, 08:29 AM
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Shift the bike into big-big (largest chainring and largest cog). If it will shift into that gear with slack to spare you can shorten the chain until it just does. However the chain must allow big-big. And no, the chain will not "stretch" enough to go completely slack just from wear.
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Old 07-26-20, 09:43 AM
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Never Fix A Running Piece. If you do not intend to use the small-small combination, and the chain is not actually slack in that combination, what advantage would shortening the badly-worn chain provide? I suspect that if/when you replace the chain you will need to replace your freewheel/cassette as well due to running with such a worn chain, so be prepared for that. At this point you may as well just run the chain-cassette combo into the ground and replace them both when the time comes.
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Old 07-26-20, 09:46 AM
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Have you measured the chain for wear?

Is the wheel all the way back in the dropouts?
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Old 07-28-20, 11:52 AM
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tommyd49
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I've had another look and yes, the wheel is well back in the dropouts.

I also measured the chain for wear again and 12 full links of the chain measures 12 1/8". I measured with a digital calliper this time - used a ruler before which was a bit bent.

I put the chain in the big-big combination and measured for slack by pulling together with a couple of small screwdrivers. There was an inch and a half of slack - i.e. one and a half links. Considering 1/8" of wear over 12", doing the maths - an extra 1/2" over the whole length of the chain due to wear makes sense.

Originally Posted by dsbrantjr
Never Fix A Running Piece. If you do not intend to use the small-small combination, and the chain is not actually slack in that combination, what advantage would shortening the badly-worn chain provide?
I mostly agree with this, but still could accidentally shift in to the position. If this happens it would be a problem, because there is so much slack in the chain that the upper pulley in the RD comes in to contact with the chain and they start grinding together.

So, I've two options:
  1. Buy and fit a new chain and hope the front cogs and cassette are OK
  2. Leave it alone and make sure to avoid shifting in to that combination.
2 certainly seems appealing. My only thought for 1 is that the cassette and front cogs don't look worn - not shaved teeth etc.
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Old 07-28-20, 12:10 PM
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The bike has a tripple, it is not intended to be used on the small ring up front and the small cog in the back. Get it out oif the small ring up front and it should be fine.
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Old 07-28-20, 12:19 PM
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1/8" of wear over 12" will almost certainly cause the chain to not mesh well with the cogs. Changing the chain would be a mistake and almost certainly make the drivetrain skip under pedalling load.

Also, there is no damage caused by running a slightly long chai, even if it's dragging over the derailleur jockey wheels or front derailleur cage - unless you ride like that for a long long long time. When I used to assemble bikes I would adjust the limit screws on the front derailleur so it made a bit of noise when cross chaining (either big-big or small-small) as a kind of 'alarm' that you were in a bad gear. If the chain on your bike makes noise when in small-small, just treat it as a reminder not to cross chain.
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Old 07-28-20, 12:28 PM
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If the chain is still under tension in the small/small combination, and the long lower stretch isn't rubbing against the chain wrapping around the upper jockey wheel, then you're all good - this is as slack as it's going to get, and as others have said, you're not likely to be using this chainring-sprocket combination in the wild. But if you're concerned, you could likely remove a link or two, as long as it doesn't strain the RD in the big/big combination. Chain "stretch" is a separate unrelated issue. The chain seems worn based on your measurements, so it's likely the cassette is too (there's no real way to evaluate wear just by eyeballing) - since the chain and cassette are likely worn in together, I would just jeep riding them until the shifting starts to deteriorate and/or the chain starts skipping, then replace both at the same time
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Old 07-28-20, 12:29 PM
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So if the chain is worn, to the tune of 2x the traditional limit (1/16" over 12"), why would replacing it be a "mistake"?
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Old 07-28-20, 12:31 PM
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So what functional issues are you having while riding and shifting the bike? With a 3x front your small small combo is quite a bit more chain for your DR to take up than on a typical 2x bike.

If the bike shifts well while riding, then don't be imagining things wrong.

But if you must, then please show a photo in the big big combo and maybe we can know a little better if you can take a link out to make it have the look you want. <grin>
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Old 07-28-20, 12:38 PM
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Your small-small derailleur position is exactly what I set my triples up to. I wouldn't change anything (except get a new chain and probably cassette and maybe chainrings. (Now it is possible the new chain will flunk the large-large combo. I always insure I can 1) get into that gear and 2) it isn't a strain on the derailleur to do so. I don't like walking home.)
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Old 07-28-20, 02:56 PM
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Originally Posted by Iride01
So what functional issues are you having while riding and shifting the bike? With a 3x front your small small combo is quite a bit more chain for your DR to take up than on a typical 2x bike.

If the bike shifts well while riding, then don't be imagining things wrong.

But if you must, then please show a photo in the big big combo and maybe we can know a little better if you can take a link out to make it have the look you want. <grin>
Originally Posted by Litespud
If the chain is still under tension in the small/small combination, and the long lower stretch isn't rubbing against the chain wrapping around the upper jockey wheel, then you're all good - this is as slack as it's going to get, and as others have said, you're not likely to be using this chainring-sprocket combination in the wild.
The issue is that the above does happen, i.e. the lower part of the chain does rub against the RD top jockey wheel. They grind together, which in turn pushes the chain off the centre of the RD jockey wheels, so the chain basically locks up. This is something I'd like to avoid in case of shifting to the combination even by mistake.

I should point out that I plan to sell this bike to a friend for cheap. When I picked it up I thought it could be a decent runner if I could fix issues with the gears. Hence me preferring to fix the issue.

I did try to make a video showing the slack in the big-big combination. I posted it on Youtube - link here. Feel free to watch and tell me if you think it's a good look.
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Old 07-28-20, 03:07 PM
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If the vid is the big big, then you probably can take a link or two out of the chain.

Chain looks old, have you measured the distance between the pins? If you put a decent metal tape or scale up to it and the pin near the 12 inch mark is over by 1/8 inch then it's well beyond life. Many replace them when they get beyond 1/16".
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Old 07-28-20, 03:36 PM
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Originally Posted by tommyd49
The issue is that the above does happen, i.e. the lower part of the chain does rub against the RD top jockey wheel. They grind together, which in turn pushes the chain off the centre of the RD jockey wheels, so the chain basically locks up. This is something I'd like to avoid in case of shifting to the combination even by mistake.

I should point out that I plan to sell this bike to a friend for cheap. When I picked it up I thought it could be a decent runner if I could fix issues with the gears. Hence me preferring to fix the issue.

I did try to make a video showing the slack in the big-big combination. I posted it on Youtube - link here. Feel free to watch and tell me if you think it's a good look.
if the chain is rubbing then you should take out 1-2 complete links to shorten it and pull the cage downward. Put it in big/big, see how far forward you can push the lower jockey wheel forward. Every 1/2” you can push it forward before it gets strained equates to ~1” of chain (1 complete link) you can remove Just ensure that you don’t remove so many links that the RD is against its forward limit when in big/big
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Old 07-28-20, 04:50 PM
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Here is the Shimano Service instruction for that model DR....
https://si.shimano.com/pdfs/si/SI-U-005-000-00-ENG.pdf


They do the big big + 2 links. And this is without the chain running through the DR's pulley wheels. However still this isn't a guarantee. You still need to be aware of all the places for concern regarding the chain length as specs on paper can't guarantee your specific setup isn't unique in some way.
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Old 08-02-20, 03:00 PM
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So everyone, thanks for all of your tips so far.

I've had more of a thorough look at the bike over the weekend. I gave the rear derailleur a thorough lube as well as taking the rear wheel out and properly pushing it as far back in the dropouts as I could.

I then took it for a test ride. In the small-small combination, the chain is still rubbing against the derailleur jockey wheel. Difference now is that it's rubbing quite a bit less, so it's not causing the chain to come off the derailleur jockey wheel. Definitely an improvement.

Having said that, I have to say the bike does ride quite nicely and everything else is in pretty good condition. For the sake of £25 or so, I'm tempted to buy a new chain and cassette just to do the job properly. Hopefully, I won't need new chainrings. If I do, I'll probably not bother as it's getting a bit more pricey.

So, when do you normally change chainrings/cranksets? Do you tend to do them whenever you change the cassette or do you tend to wait a bit longer? I personally have never changed chainrings (or even cassettes maybe) on my own bikes as I've usually replaced the chain fairly early.

P.S. Iride01 - I'm impressed you found the manual for the derailleur on the Shimano website - I'm amazed they have one for such an old component! If I don't get a new chain I may well shorten it one link, although it's not quite so bad in big/big now.

Last edited by tommyd49; 08-02-20 at 03:05 PM.
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