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Tandem Chain Snaps Often

Old 12-20-21, 12:31 PM
  #1  
Mr_Pickles3
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Tandem Chain Snaps Often

Hi all

I have a 1980s Peugeot tandem which I restored myself last year and has done around 300 miles since. Yesterday, the rear sprocket chain snapped for the third time: the first two times were because of me stupidly installing the chains incorrectly, but, in the most recent incident, the chain was a "new" KMC chain (correctly installed this time!) that has been on the bike for 8 months. It failed by a link exploding, with the pin coming out of the hole and leaving its two plates bent outward as my friend and I were pedalling hard to move off from stationary up a steep hill. Unfortunately, despite carrying an emergency quick-release link, we had to be rescued by a nearby homeowner/cyclist with a pin extractor tool as I had forgotten mine.

Basically, I have a few questions:
1. Are specialist tandem chains available? If not, which chains are more durable/stronger that I could use to prevent this happening again so soon?
2. Is this a common problem with tandems?
3. Is there a riding technique to reduce the chances of this happening?
4. The chain also skipped/skips frequently when under load on the two lowest rear sprocket gears despite them having little wear. What might cause this and how can I resolve it?

About the bike: it is 10-speed with a 5-speed freewheel and 2 chainrings; the freewheel and chainrings are original but have little wear (as confirmed by a bike shop mechanic); and it has friction shift gears.

Any help of info would be great!
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Old 12-20-21, 01:17 PM
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Please describe "Installed correctly"?
Your chain skips because your freewheel is worn out.
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Old 12-20-21, 01:20 PM
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I suspect this failure was caused by a loose nut in the saddle.

A chain is very easy to break if you shift under load. You need to finish your shifts before you are climbing the steep hills. It is possible that the plates on this broken link were peeled apart some time before the eventual snap, and it just chose that moment to let go. But shifting under load is a primary cause.
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Old 12-20-21, 01:57 PM
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My stoker and I have never broken a chain in 20+ years. But, it is possible under load, as you have demonstrated. (We are not overly powerful)
The only tandem spec chains I have seen were longer than the average bear chain but not more rugged. You use 5-6 speed chains?
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Old 12-20-21, 05:12 PM
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Originally Posted by trailangel View Post
Please describe "Installed correctly"?
out.
I used the quick-link supplied to connect the two ends rather than pushing out a pin and joining it together.

Originally Posted by ClydeClydeson View Post
I suspect this failure was caused by a loose nut in the saddle.

A chain is very easy to break if you shift under load. You need to finish your shifts before you are climbing the steep hills. It is possible that the plates on this broken link were peeled apart some time before the eventual snap, and it just chose that moment to let go. But shifting under load is a primary cause.
Right, looks like Iíll have to be strict with my stokers! My different friends enjoy riding it with me, and some of them donít get the idea of easing off when I say ďchangeĒ as well as others!

Originally Posted by JanMM View Post
My stoker and I have never broken a chain in 20+ years. But, it is possible under load, as you have demonstrated. (We are not overly powerful)
The only tandem spec chains I have seen were longer than the average bear chain but not more rugged. You use 5-6 speed chains?
Interesting and reassuring that itís preventable. Two of the failures occurred when moving off from a standing start on *very* steep inclines where both of us were giving our all to get going. Looks like thatís probably the primary reason.

Thanks everyone
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Old 12-20-21, 10:03 PM
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During my 12-14k miles as stoker we lost the chain 3x. Once the timing chain came apart for no apparent reason (moving
at ~15 mph on level without accel). It was repaired with a quick link IIRC. The other two were drive chain, once when
starting up a 10% grade and a side link ruptured at the narrow waist between the pins: the other was at the beginning of
a hill, ~3% grade with a mild push on when a quick link came apart. We found the parts, re installed them and the
chain functioned fine for hundreds of miles after ward. In general we found drive chains (10 spd) were good for ~2000
miles when they were clearly worn out and timing chains lasted ~10k miles.

FWIW a $10 Park chain tool is a 4-5 oz addition to your tool kit, where its presence will innoculate you against further failures.
Always keep a couple of quick links in the tool kit as well.
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Old 12-20-21, 10:58 PM
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Some teams don't mesh well on a few tandeming aspects. An important one, for riding more than a few miles, is cadence compatibility. Another is the stoker is unable to see the road and situation directly ahead. Which brings us to trust and communications.

Captains need to call out shifts a few pedal strokes before they shift. How much before is part of the tandem experience. Captains need to anticipate the road they are heading to before they get there. The stoker doesn't know when the hill kicks up, or a rough spot needs standing over, unless the captain says something.

In time most teams do tend to learn how to work better with each other and the demands the tandem has too. Part of that is the added stresses two riders place on stuff made for one and how to minimize the worst.

And captains need to know that whatever happens bad it's their fault... and that they need to keep riding back to the car Andy
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Old 12-21-21, 09:04 AM
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Originally Posted by Mr_Pickles3 View Post
I used the quick-link supplied to connect the two ends rather than pushing out a pin and joining it together.
Did it fail at the quick-link, or someplace else? What specific chain manufacturer/model is it?

Right, looks like I’ll have to be strict with my stokers! My different friends enjoy riding it with me, and some of them don’t get the idea of easing off when I say “change” as well as others!
Are the cranks in phase or out of phase? If in phase, you might try mounting them out of phase so captain and stoker power strokes happen at different times.
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Old 12-23-21, 09:41 AM
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We have been riding tandems for 40 years and never broke a chain.
I am not sure it is even possible to apply enough force to break one unless the force is coming from the side.
Maybe your chain line is severely off or some other problem with the bike.
Another possibility is defective or counterfeit chains.
Discovered due to the shortage there a lot of counterfeit chains out there.
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Old 12-24-21, 10:58 AM
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Originally Posted by jnbrown View Post
We have been riding tandems for 40 years and never broke a chain.
I am not sure it is even possible to apply enough force to break one unless the force is coming from the side.
Maybe your chain line is severely off or some other problem with the bike.
Another possibility is defective or counterfeit chains.
Discovered due to the shortage there a lot of counterfeit chains out there.
We've also been riding tandems for over 36 years, and the only chain we've ever broken was due to a defective derailleur issue (a story in itself). I agree that something is likely problematic with the bike, whether it be in the chain alignment, bent derailleur hanger, worn freewheel, or possibly a combination of a few things. Perhaps some close-up pics of the drivetrain might help?
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