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New chain wrecked already?

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New chain wrecked already?

Old 06-18-10, 04:43 AM
  #1  
MarkN
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New chain wrecked already?

I replaced my chain and cassette 2 weeks ago, SRAM PG971 chain and SRAM PG980 cassette (9speed). They've done about 150 miles without any problems... until now. Earlier, as I was leaving a set of traffic lights, the gears crunched and failed to engage (I hadn't shifted down properly due to having braked hard at the lights). For the rest of the journey the chain skipped and made irritating noises every few pedals.

chain..jpg
Sorry about the poor quality, my camera phone is rubbish so I tried to paint in the details.

It seems that one of the connections in the chain has deep scratch at the join, which has made it inflexible. It bends under force, but not at all when going round. Seems like it would cause a lot of wear on the cassette and chain wheel. The only solution I can think of is to remove that link and try and file back the scratch. Is that possible? Otherwise... I dunno. Is it salvageable or a write-off?

Last edited by MarkN; 06-18-10 at 04:49 AM.
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Old 06-18-10, 05:13 AM
  #2  
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Using your fingers, try bending the chain sideways and back-and-forth to loosen the link. Make sure it's well oiled. Report back.
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Old 06-18-10, 05:40 AM
  #3  
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Using fingers, it bends but not much and takes a fair bit of force to do so. It locks at about 60 degrees from straight turning clockwise, and 40 degrees from straight anticlockwise while other links bend freely. Plenty of oil.
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Old 06-18-10, 05:52 AM
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You could try these steps before ditching the chain.
http://bicycletutor.com/stiff-chain-link/
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Old 06-18-10, 05:52 AM
  #5  
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I don't think any amount of oil is going to help that cracked roller. That chain (or at least, that link) needs replaced. It could just be a defective part, but I'd give the rest of your drive train a close inspection, to make sure some other undiscovered damage didn't cause (or was caused by) the carnage.

If you have a chain tool, you might be able to loosen that link up a little, but I'm not sure I'd want to trust it for very long.
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Old 06-18-10, 05:59 AM
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Originally Posted by Greyryder View Post
...cracked roller...
I'd thought that part was a reflection. Ignore my earlier posts.
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Old 06-18-10, 07:07 AM
  #7  
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When you crunched down on that bad shift you dinged the link. It might be spreading the inner plates causing binding the link. It might also be a ding running across two outer plates which I've seen peen the metal in such a way as to make the two plates click together. This problem is more common on mountain bikes than road bikes but easy to fix.

So all is not lost, and you have 3 basic choices to solve the problem.

1- if it'll run sort of OK and not skip badly you can ride it this way and the highest spot will wear quickly and the chain will fix itself. Yours looks pretty bad and this might not be an option.
2- carefully file the peened part off using a small triangular or knife file. It doesn't have to be beautiful, you just want to ease the pressure, or at the edges of the plates, eliminate the interlock. If you own a Dremel tool use one of the disc shaped stones for the job. It's a few minutes work and the chain will be 100% good as new when your done.
3- if your chain is long enough, cut out the problem area and re-splice with another connector. If you can't shorten the chain, use two connectors to splice in a piece hopefully saved when you first cut the chain to install it.
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Old 06-18-10, 10:46 AM
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Given the money you've just spent on the 980 cassette, I would replace at least that section of chain or remove the troubled area if you will still have enough chain to do so without impacting the big/big combo.
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Old 06-18-10, 11:14 AM
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Since these items are new, contact the mfr for warranty. A little force at startup shouldn't have killed the chain. I've done this 2-3x per year with no ill effect on my KMC chain and SRAM cassette.
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Old 06-18-10, 12:06 PM
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Originally Posted by furballi View Post
Since these items are new, contact the mfr for warranty. A little force at startup shouldn't have killed the chain. I've done this 2-3x per year with no ill effect on my KMC chain and SRAM cassette.
It depends on how hard and exactly where the teeth hit the chain. It isn't a warranty issue, but the dealer or Sram might replace the chain as a goodwill gesture, or maybe the dealer might discount a replacement, though it isn't needed.

Chain plates have to be somewhat ductile lest they be prone to fracture. Imagine putting a chisel across the plates, or at the edge of one and striking it.
You'd den't the plate and peen some metal over the edge making a burr which is exactly what happened to the OP. File off the burr and the chain will be as good (almost) as new.

It isn't a rare problem especially with newbie mountain bikers who jam shift under load, and a question of luck whether the burr is exactly right to jam the chain. The OP can try his luck with the dealer, or he could get out a file and be riding today.
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Old 06-18-10, 12:30 PM
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I assume you had to shorten the chain when you installed it; if so, replace the failed link with one you took out when you shortened the chain. If you did not shorten it on install, 95% chance you should have, so you can now do so by taking the faulty link out. Only way you are stuck is if you did shorten on install, but ditched the extra links... in which case at least you have learned something... Don't ditch those extra links, you won't need them if you keep them, but you will if you don't, or so says a certain Mr Murphy.
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Old 06-18-10, 12:37 PM
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Originally Posted by FBinNY View Post
3- if your chain is long enough, cut out the problem area and re-splice with another connector. If you can't shorten the chain, use two connectors to splice in a piece hopefully saved when you first cut the chain to install it.
I stopped off at a bike shop on my way home and had them do this. It seems to have worked though every little creak makes me nervous. I'll be much more gentle with it now, especially as any chance I may have had with the waranty is now, presumably, voided.

It's the city riding that does it. I tend to leave lights like a bat out of hell to get ahead of the traffic. If my head isn't in gear for whatever reason, be it work related or from a close call with a transit van, my gear shifting occasionally feels the pain.

Cheers for the help, people!

Last edited by MarkN; 06-18-10 at 12:41 PM.
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Old 06-18-10, 03:14 PM
  #13  
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If a stiff link fails to run through the rear derailleur really bad things can happen. The derailleur can be twisted around, bent, or broken. I have seen a dropout plate pulled out of the frame requiring a trip to the factory.
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