Odd transmission fault!



Martian Tom

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Aug 23, 2008
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Here's a fault that has got the chap at my local bike shop scratching his head...

I've got a Specialized Sequoia road bike, about 6 years old, which has done around 10,000 miles on all original components. It has 24 gears on a triple chain ring set. The chain rings are 30 - 52. The cassette is 11 - 25. The set-up is Shimano Tiagra.

The fault started spontaneously a couple of weeks ago. One day, I started getting a 'click' on each revolution of the chain as it passed through the cassette. On the 3 highest gears - not on any of the others - the chain jerked, like it had slipped a tooth, at the same time as the click. This went on for a couple of miles and then, just as spontaneously, stopped and everything was fine again. It stayed fine for about 30 more miles, and then it started doing it again and carried on for about 3 miles.... and then it stopped again! And that's how it's been ever since. In that time, I've covered about 250 miles and the bike's performed perfectly for 15 or 20 miles... and then I get a 3 or 4 mile stretch with the clicking and jumping. Then it's back to normal for another 15 or 20 miles. All of my cycling is done on macadam roads, and my usual routes have a variety of hills (some quite steep) and flats. I cycle fairly hard and usually average 18 mph. The fault doesn't occur at any particular time or in any particular gear, and there's nothing I can think of - a multiple shift, a change of gradient, etc - that causes it to start or stop. It just suddenly starts... then suddenly stops!

I've had the gear cables changed and everything is adjusted correctly... but it hasn't made any difference. The chap at the bike shop has suggested that the transmission might be getting to the end of its life - and a replacement would certainly cure the problem. But he still can't account for the intermittent nature of the fault.

Does anyone have any ideas, please?
 

kdelong

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Dec 14, 2006
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Check for a worn or tight bearing in the Idler and Jockey Pulleys. Lubricate as necessary. Next time that it happens, stop and check your chain for stiff link. You might have to replace the link. I think that one of the pulleys is more likely than the chain given the intermintent nature of the problem. Let us know what it was when you find out.
 

Martian Tom

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Aug 23, 2008
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kdelong said:
Check for a worn or tight bearing in the Idler and Jockey Pulleys. Lubricate as necessary. Next time that it happens, stop and check your chain for stiff link. You might have to replace the link. I think that one of the pulleys is more likely than the chain given the intermintent nature of the problem. Let us know what it was when you find out.

Thanks, kd. The jockeys are okay, but I have found a stiff link. I cleaned it up and soaked it in lube, and that's certainly helped - so that must be the problem. Weird how it's so intermittent, though. Now... I need to see if I can find that link extractor that I bought years ago but haven't yet used...
 

alfeng

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Jul 23, 2005
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Martian Tom said:
Thanks, kd. The jockeys are okay, but I have found a stiff link. I cleaned it up and soaked it in lube, and that's certainly helped - so that must be the problem. Weird how it's so intermittent, though. Now... I need to see if I can find that link extractor that I bought years ago but haven't yet used...
Was the chain replaced recently?

Who put the chain on? Even though fixing a stiff link is a 2-minute job, have him/her fix it.

If the chain wasn't replaced, then now is the time.
 

Martian Tom

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Aug 23, 2008
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alfeng said:
Was the chain replaced recently?

Who put the chain on? Even though fixing a stiff link is a 2-minute job, have him/her fix it.

If the chain wasn't replaced, then now is the time.

No, it's the original chain. The chap who originally assembled the bike fixed the link for me this afternoon. The chain now runs perfectly. I asked about replacing the chain, but he advised against it as it might not 'run' with the existing components. He said it's better to replace everything when the time comes.

Any views on this?
 

Dietmar

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Jun 9, 2006
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Martian Tom said:
No, it's the original chain. The chap who originally assembled the bike fixed the link for me this afternoon. The chain now runs perfectly. I asked about replacing the chain, but he advised against it as it might not 'run' with the existing components. He said it's better to replace everything when the time comes.

Any views on this?

Nonsense. Typical cassette life is at least three times the chain life, chainrings usually last even longer.
 

Martian Tom

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Aug 23, 2008
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Dietmar said:
Nonsense. Typical cassette life is at least three times the chain life, chainrings usually last even longer.

Thanks, Dietmar. I checked the cassette and the chainrings and thought they seemed okay. There's not a problem now, so I'm just going to wait until something breaks. I guess these guys have to make a living somehow...
 

Dietmar

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Jun 9, 2006
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Martian Tom said:
Thanks, Dietmar. I checked the cassette and the chainrings and thought they seemed okay. There's not a problem now, so I'm just going to wait until something breaks. I guess these guys have to make a living somehow...

Uhh, no, don't wait until something breaks. You really need to replace the chain once it's worn, because if you don't, you will start wearing out your cogs and chainrings really quick, and then you really have to replace everything. Bicycle stores sell chainwear indicator tools for a few bucks that you can use, or, read the material on chain wear on Sheldon Brown's website.
 

dhk2

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Aug 8, 2006
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As dietmar said, checking the chain often with an indicator gauge or just by measuring with an accurate steel rule is the best policy. Just letting everything go until the chain skips or fails is an option, but it's not fun to discover a problem on a long ride with hills to climb.

Cassettes can be worn out without showing any visual wear. If you put a new chain on a worn cassette, it will skip under load. My experience has been two chains to each cassette replacement.....about 5K miles/chain, so 10K per cassette.

Have replaced chainrings once, at 18K miles. Thought it was time because I noticed a lot of "play" in the pedal, and could see the chain moving up on the teeth under a static load on the pedal on the middle chainring. Replaced all three as a set, and the result was a quieter and smoother ride.

These wearout parts aren't cheap, but IMO vital to keep your bike quiet, smooth and safe. Getting that "new bike" feel back without having to buy a new bike isn't a bad deal :)
 

Martian Tom

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Aug 23, 2008
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Dietmar said:
Uhh, no, don't wait until something breaks. You really need to replace the chain once it's worn, because if you don't, you will start wearing out your cogs and chainrings really quick, and then you really have to replace everything. Bicycle stores sell chainwear indicator tools for a few bucks that you can use, or, read the material on chain wear on Sheldon Brown's website.

Thanks for the link, Dietmar - no pun intended :D
Point taken, too.
 

Martian Tom

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Aug 23, 2008
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dhk2 said:
As dietmar said, checking the chain often with an indicator gauge or just by measuring with an accurate steel rule is the best policy. Just letting everything go until the chain skips or fails is an option, but it's not fun to discover a problem on a long ride with hills to climb.

Cassettes can be worn out without showing any visual wear. If you put a new chain on a worn cassette, it will skip under load. My experience has been two chains to each cassette replacement.....about 5K miles/chain, so 10K per cassette.

Have replaced chainrings once, at 18K miles. Thought it was time because I noticed a lot of "play" in the pedal, and could see the chain moving up on the teeth under a static load on the pedal on the middle chainring. Replaced all three as a set, and the result was a quieter and smoother ride.

These wearout parts aren't cheap, but IMO vital to keep your bike quiet, smooth and safe. Getting that "new bike" feel back without having to buy a new bike isn't a bad deal :)

Well... I've done just over 10,000 miles now on the original components with no previous problems. Since I had that stiff link fixed yesterday, I've covered about 30 miles without a hitch - no skipping or slipping, everything working as smoothly and quietly as normal. I'll check out the chain, though - and I may just change everything anyway soon. It's probably about due.
 

kdelong

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Dec 14, 2006
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I have heard that a lot of chain wear indicators are inaccurate so I have never really tried them. I always measure with a caliper, but a good machinist's steel rule would work just fine I guess. Anybody have any recommendations on a good Accurate wear indicator?
 

Dietmar

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Jun 9, 2006
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kdelong said:
I have heard that a lot of chain wear indicators are inaccurate so I have never really tried them. I always measure with a caliper, but a good machinist's steel rule would work just fine I guess. Anybody have any recommendations on a good Accurate wear indicator?

The simple CC-3 from Park Tool works fine, and is reputed to be quite accurate. They also have a thing they call Chain Checker (CC-2), which is more fancy (gives continuous readings). I have tried both, and they both do what they're supposed to do. On the other hand, the tried-and-true steel rule works just fine.
 

Martian Tom

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Aug 23, 2008
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Hm... I've checked with a rule and the rivet is between 1/16 and 1/8 past the inch mark - closer to 1/8. So, that probably means replacing the lot. Any idea how much life I might still have in the chain? :confused:
 

dhk2

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Aug 8, 2006
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1/8" stretch over 12" of chain would be 1% stretch. From what I've read, this is what industry standards say is a worn-out chain. Some people try to replace the chain at 1/16", or 0.5% wear. The Park CC-3 gauge has two sides: one gauges 0.75%, the other 1%. I use the 0.75% limit, which comes up in 4-6K miles. I've also heard that the accuracy may be questionable, since it measures the inter-roller distance and not the pin distance, but seems to work just fine for me on Shimano and SRAM chains.

If you've got 10K miles on your original chain and cassette, I'd bet it's time to replace them both. You could always have your LBS take a look to be sure.
 

artemidorus

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Mar 10, 2004
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After 16,000 km, your chain is probably well over 1% stretched. Your cassette and your favourite chainring are probably already sufficiently worn as to prevent them working with a new chain. I would take the advice of your LBS and ride until something stops working, rather than replacing any of the drivetrain now, unless you spend a lot of time standing out of the saddle, in which case I would replace chain and cassette now. When you replace the chain, check to see if it slips with any of your chainrings. Don't do the test standing out of the saddle.
 

Martian Tom

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Aug 23, 2008
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artemidorus said:
After 16,000 km, your chain is probably well over 1% stretched. Your cassette and your favourite chainring are probably already sufficiently worn as to prevent them working with a new chain. I would take the advice of your LBS and ride until something stops working, rather than replacing any of the drivetrain now, unless you spend a lot of time standing out of the saddle, in which case I would replace chain and cassette now. When you replace the chain, check to see if it slips with any of your chainrings. Don't do the test standing out of the saddle.

I don't do a lot of standing out of the saddle. We've only got a couple of hills around here where that's necessary - and even then, they're generally negotiable without standing given the range of gears I've got. The whole thing is running as sweet as a nut at the moment, so I'm loathe to touch it. Most of my cycling is done within a 15-mile radius of home, and if I did have a serious breakdown it wouldn't be too much of a problem to get back. I'll just carry on for now and see how it goes... :cool: