Broken Chain

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Broken Chain

Postby r11ss » Tue Nov 05, 2013 8:29 pm

Hi, I would appreciate opinions on why I keep braking chains. I regularly measure them for wear with a park tools chain checker, clean and oil them with Squirt lube and don't cross chain. I am 100kg however I would have thought it would be near impossible to break a chain through pushing the pedals.
Last edited by r11ss on Tue Nov 05, 2013 8:45 pm, edited 1 time in total.
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by BNA » Tue Nov 05, 2013 8:32 pm

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Re: Broken Chain

Postby Percrime » Tue Nov 05, 2013 8:32 pm

is your name Clark Kent? Are these chains rusty and never oiled? Or did they cost $5?
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Re: Broken Chain

Postby QuangVuong » Tue Nov 05, 2013 8:33 pm

Is that a Shimano chain? If it is, then you installed it backwards.

If not, then try using a non hollow chain. Hollow chains look cool and save weight, but are relatively weaker.
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Re: Broken Chain

Postby r11ss » Tue Nov 05, 2013 8:33 pm

New Ultegra chains and looked after. I am trying to get a picture up but struggling with the technology.

"https://www.dropbox.com/s/fv30t67zzp3bf8m/Photo%205-11-2013%208%2042%2056%20pm%20%28HDR%29.jpg"
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Re: Broken Chain

Postby r11ss » Tue Nov 05, 2013 8:41 pm

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Re: Broken Chain

Postby r11ss » Tue Nov 05, 2013 8:51 pm

This one may have been a SRAM chain however I broke an Ultegra exactly the same way this morning,
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Re: Broken Chain

Postby Duck! » Tue Nov 05, 2013 8:52 pm

That chain is mounted the wrong way (if it's Shimano). The side with the solid outer link plates faces outboard.

Are they breaking where you joined them? If so, you may have an incompatible chain tool which doesn't brace the back of the link sufficiently (due to being too wide for the chain) when the pin is pushed in.
I had a thought, but it got run over as it crossed my mind.
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Re: Broken Chain

Postby r11ss » Tue Nov 05, 2013 9:18 pm

The one on the wilier is sram red and hose those slots both sides. The one below is ultegra and was fitted by a mechanic. It didn't break anywhere near the joint.Image

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Re: Broken Chain

Postby jacks1071 » Tue Nov 05, 2013 9:46 pm

I'm guessing you are changing gears under heavy load, the drivetrain is not designed for that.

Try to change gears in the deadspot of the power stroke and/or back the power off when shifting.
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Re: Broken Chain

Postby singlespeedscott » Tue Nov 05, 2013 9:55 pm

+1
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Re: Broken Chain

Postby biker jk » Tue Nov 05, 2013 9:59 pm

Duck is correct in that the chain was fitted wrong way around but I doubt that caused the breakage. Is it a 6700 or 6701 model chain? The first batch (6700) had quite a lot of breakages like yours so Shimano fixed the problem and released the 6701 model. If it's a 6701 chain and you're breaking them then jacks1071 is likely correct regarding changing gears under load.
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Re: Broken Chain

Postby human909 » Tue Nov 05, 2013 10:10 pm

WOW!

A poorly set front derailleur can easily strip a plate and break a chain. If it is too low on the the tube shifting might be fine but it could set up the conditions for a plate strip. This occurs from a scissoring action between the derailleur, the chain wheel and the moving chain. The chain can break even under relatively moderate load.

That said being 100kg and running lighter chains certainly wouldn't help. Most chain breakages are cause by some other factor that can increase the stress on the chain. Shifting under load increased stress, combine that with your weight and uber power then you might be able to break a chain even on a properly configure bike. In which case get a stronger chain! (Or weaker muscles!)
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Re: Broken Chain

Postby Duck! » Wed Nov 06, 2013 6:16 pm

biker jk wrote:Duck is correct in that the chain was fitted wrong way around but I doubt that caused the breakage. Is it a 6700 or 6701 model chain? The first batch (6700) had quite a lot of breakages like yours so Shimano fixed the problem and released the 6701 model. If it's a 6701 chain and you're breaking them then jacks1071 is likely correct regarding changing gears under load.

That dodgy batch of chains has been out of circulation for at least three years, so we can probably discount that. Moreso given that the OP points out he's also breaking other chains.

I think, as H909 & jacks1071 suggest, it's a combination of setup and technique.
I had a thought, but it got run over as it crossed my mind.
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Re: Broken Chain

Postby r11ss » Thu Nov 07, 2013 5:29 am

Hi, thanks for all the input. The chain on the Wilier is SRAM red with those slots both sides. Yesterday's break was on a cervelo s5 with Ultegra groupset and chain. I have not noticed any chain rub from the front derailleur on either bike. Interestingly both breaks happened on the same Tuesday ride that I do, shortest ride of the week, 35k's, and lots of short sharp hills. Because the ride is so short we try to smash the hills, both times the break was on a 500m 17% hill. I take the point about changing under load, I try to ease off at the change point but sometimes this is not easy when climbing or sprinting. I was hoping for an easy answer and that this is a more regular occurrence for some people, obviously not. I might just have to change my chain earlier.
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Re: Broken Chain

Postby winstonw » Thu Nov 07, 2013 6:18 am

recheck your sram chain. from the photo, it looks like the link behind the broken one doesn't have a slit in it.
- what exact gear are you in when the chain breaks? i.e. 34:21 ?
- was your last change of the front or rear der, and did it occur quickly and cleanly?
- roughly how low a cadence are you getting down to on that pinch, and speed?
- get a good mechanic to check your chainrings. in the photo it looks like there's some teeth worn much more than others.
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Re: Broken Chain

Postby Nate » Thu Nov 07, 2013 6:50 am

Use quick links when joining too
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Re: Broken Chain

Postby greyhoundtom » Thu Nov 07, 2013 8:48 am

winstonw wrote:- get a good mechanic to check your chainrings. in the photo it looks like there's some teeth worn much more than others.

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Re: Broken Chain

Postby Duck! » Thu Nov 07, 2013 12:58 pm

Nate wrote:Use quick links when joining too

Why? It has nothing to do with the link breakage the OP is experiencing.
I had a thought, but it got run over as it crossed my mind.
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Re: Broken Chain

Postby r11ss » Thu Nov 07, 2013 2:31 pm

I guesss I was on 34:23 on the ultegra, probably 39:25 on the sram. About 70 cadence maybe 12kph

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Re: Broken Chain

Postby r11ss » Thu Nov 07, 2013 2:35 pm

I will get the chainring checked, I think sram have different teeth to help with changing gears though

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Re: Broken Chain

Postby singlespeedscott » Thu Nov 07, 2013 3:15 pm

Definitely sounds like shifting under high torque load to me.
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Re: Broken Chain

Postby winstonw » Thu Nov 07, 2013 8:47 pm

yes, pushing 100kg + bike/gear weight is a big load.....you might get your frame checked carefully too. you might even have a crack that is permitting excessive flex, or the frame might be flexing excessively without a crack under your weight.

if the chain break is not occurring straight after a gear change, then it seems more likely your gear selection is too high (though your cadence doesn't indicate that), or frame flex or chainring anomalies (uneven teeth or lateral flex) might be an issue.

let us know what it ends up being....it's an interesting case.
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Re: Broken Chain

Postby eeksll » Thu Nov 07, 2013 11:39 pm

I forced a shift small chain ring to big chainring while going up a hill slow cadence.

Heard a crack, the FD had pivoted on the braze on bolt. Can't see any cracks in the carbon so assume the crack was from the bolt letting go/slipping.

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hmmm I might go check my chain now too ... ekkk
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Re: Broken Chain

Postby r11ss » Fri Nov 08, 2013 6:46 am

All good points however with two different bikes most of them can't apply. Can anyone recommend a chain that is going to be strongest.

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Re: Broken Chain

Postby Nate » Fri Nov 08, 2013 9:13 am

Duck! wrote:
Nate wrote:Use quick links when joining too

Why? It has nothing to do with the link breakage the OP is experiencing.


If he carried a few spare quick links he'd be up & running on the road for one ;)

Just removing any possibilities - not just for the OP but for others too.
"correct use" of the tools & joining pins should yield no issues - but for a few $, a re-usable quick link makes life SO much easier - especially come maintenance time.
Others may also accidentally put a bit too much stress in the wrong place when using the tools & have the same issue.

If there's better & simpler ways of doing things & removing the possibility of damage/failure - i will suggest them!
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