Chain snapping issue

[gairym]

So.....I've done three (big) rides now on my new 1x9 set-up and each time I've had the chain snap on me!

Here's some diagnostically relevant info:

- Brand new chain, chainring, cassette, mech, shifter and cables.

- Chainring (Surly 32T), Cassette (Deore 12-36T), Chain (Sram PC971), Mech/Shifter (Sram X7)

The chain seems to be splitting apart from within in that it's breaking apart outwards as if it's being forced weirdly somehow???

My two thoughts are that it's either the narrow chain being pressured apart by the wide steel single-speed chainring or that the lateral stresses of always using the middle ring with both upper and lower extremities of the cassette are to blame.

Or.....it's a combination of the two?

Has anyone else had similar issues?

I used to ride in everything from 1st to 9th on my middle ring whilst running 3 chainrings and so I don't see why this new set-up should be causing me hassles.

This is my first foray into all things Sram (had finally had enough of Shimano being impossible to fine-tune after the first week's use) and so maybe there are other 9sp chains that might be a little wider internally?

Maybe I should file-down the chainring teeth so that they're a little narrower?

What do you think?

Any/all advice appreciated.

Gairy.

[Matt]

Had a SRAM chain that kept breaking.

Swapped it for another identical chain and it's been fine, reckon it was a duff chain from day 1

[pedalhead]

What's the BCD of the chainring? 104? This is from Surley's website...

* Our 94bcd,104bcd and 110bcd x 34/35/36t chainrings are made with a 2.2-2.3mm thick stock plate and work best with 5-8 speed chains. Many folks are using these on 9 speed drivetrains but this can often results in a "tight fit" right out of the box (This will loosen up and shifting should improve after the chain breaks in). The 110bcd 38-50t and all 130bcd chainrings are machine finished to have a 2.1mm tooth thickness and thus work fine with 9spd chains.

They don't mention the 32 but I wonder if the chainring is slightly too wide for the chain. If you turn the cranks slowly, does it look like the chain is settling into the teeth easily or is there a lot of friction?

[Bearbonesnorm]

Couple of thoughts.

There's a pic of your bike somewhere on the forum and the rear mech is pulled a long way forward (obviously you're in your biggest gear). Could be the chain is a couple of links shorter than ideal.

Not all mechs will work with a 36t cassette. I don't think SRAM produce a 36t cassette so I wouldn't be surprised if their mechs weren't the best choice..

Neither of the above actually explains your chain breaking but it might be somewhere to look ... are you always in the same gear when it snaps? An 'easy' gear produces more torque so puts more strain on the chain, ie most chains snap when in granny ring (I know you haven't got a granny ring)

[chris n]

Does it break at the same link each time, or in different places on the chain? Is it at the links you've riveted back together?

[gairym]

Had a SRAM chain that kept breaking.

Swapped it for another identical chain and it's been fine, reckon it was a duff chain from day 1

i've had that before too - maybe i'll try a new one and see if it still happens.

What's the BCD of the chainring?

yeah, it's a 104.

(This will loosen up and shifting should improve after the chain breaks in)

they mention the chain 'breaking in' not 'breaking off'.

it does feels snug when i turn the cranks slowly but there's nothing perceptible when riding.

There's a pic of your bike somewhere on the forum and the rear mech is pulled a long way forward (obviously you're in your biggest gear). Could be the chain is a couple of links shorter than ideal.

Not all mechs will work with a 36t cassette. I don't think SRAM produce a 36t cassette so I wouldn't be surprised if their mechs weren't the best choice..

yeah, i was thinking that too but, as you say, it still doesn't explain the snapping.

what's the reasoning behind using short-cage mechs for 1x9 duties? i ask as i've got my old XT (long-cage) mech laying around the place and so could revert to (un)trusty shimano if the problem persists.

Does it break at the same link each time, or in different places on the chain? Is it at the links you've riveted back together?

nope - different places every time.

it's a puzzler!

[pedalhead]

what's the reasoning behind using short-cage mechs for 1x9 duties? i ask as i've got my old XT (long-cage) mech laying around the place and so could revert to (un)trusty shimano if the problem persists.

For a single chainring setup, there'll be less slack on the chain for the mech to take up, so you can get away with a shorter cage. Fwiw, I kept snapping 9 speed SRAM chains on my singlespeed & have now moved over to using KMC 8 speed chains. Not of much use to you though!

[Ian]

What model of chain are you using?
The Sram cross-step riveted ones are better than the ones that are only riveted in one direction. I've had the latter break on me before, but never the former.

Or, try a KMC chain and see if you still get the same problem. If that breaks too, then there's a greater likelihood of there being something else in the system that is causing a strain that the chain can't take.

[Bearbonesnorm]

I suppose you could have a 'Friday afternoon' chain which would explain it all.

Gairy will it pedal backwards okay without any noises or chain skipping issues?

[Ian]

on my singlespeed...have now moved over to using KMC 8 speed chains. Not of much use to you though!

Brief highjack - I've got a 8sp chain, also KMC, on my bike now too, having moved over from an 1/8" chain (save weight). Twice out of the last three rides I've managed to pop the chain off the sprocket/ ring. All components are new and the chain is definitely not slack. Has such a thing happened on yours?

[pedalhead]

on my singlespeed...have now moved over to using KMC 8 speed chains. Not of much use to you though!

Brief highjack - I've got a 8sp chain, also KMC, on my bike now too, having moved over from an 1/8" chain (save weight). Twice out of the last three rides I've managed to pop the chain off the sprocket/ ring. All components are new and the chain is definitely not slack. Has such a thing happened on yours?

Nope, mine hasn't come off the chainring. But, this KMC chain does seem to stretch (wear blah) quite a lot. I find myself having to tension the chain quite a lot. It's possible there's a bit of EBB slippage going on, I keep meaning to measure the chain to find out.

[gairym]

What model of chain are you using?
The Sram cross-step riveted ones are better than the ones that are only riveted in one direction. I've had the latter break on me before, but never the former.

Or, try a KMC chain and see if you still get the same problem. If that breaks too, then there's a greater likelihood of there being something else in the system that is causing a strain that the chain can't take.

it's the latter.

i think my order of potential solutions should be:

1. try another of the same chain (as i have one and it'll let me know if it was just a duff chain).

2. try a different chain (a KMC for example).

3. change to a non-single-speed chainring (maybe find a nice Middleburn or something).

4. if all of the above fails i might have to start looking at the mech/cassette compatibility.

should do the trick!

thanks for all the advice - appreciated.

[gairym]

ok, i changed the chain (like for like), shifter and mech (from Sram X7 to X9 - amazing eBay bargains) and did a 2 hour ride which produced some light intitial chain-suck (soon disappeared), some mild grumbling but no chain snap!!!

let's hope it was just a duff chain (as that'd be he cheapest/simplest solution).

also.....

to highjack a thread i started.....

i've just received my new xc/flat bars (the only 'flat' bars i've ever owned in 15+ years of mtbing) and it's WEIRD!!!

amazing the difference it makes on the road and technical climbs (really felt in control) but definitely a compromise on the very technical descents (i went over the bars for the first time in about 10 years).

all-in-all, i think i might like it (and i'm even getting used to the look of a bike of mine with non-riser bars on it) - only time will tell.....