Ggrhh. Why does my chain keep breaking?

Sat: Two months old (as is cassette and rings) and broke twice on Sat while under med-high load. Plates seemed to be exploding outwards if anything. Also took the liberty of snapping the pin on my Park chain tool too.

Mon: Same chain broke 3 times under med-high load within metres of each other, eventually taking the mech hanger with it. As before, plates kind of bending outwards.

Wed: Fitted new chain and the **** thing has gone again. Plates fine, but inner link somehow popped out without any distortion.

Shimano HG93 for the record (XT mech and cassette).

Really pissing me off now. Was supposed to be out this afternoon. Mate popped round Mon night and said he didn’t see anything wrong either.

Ggrhrhrhgrhrh!

how are you fixing the chain on ?

Get a sram chain or power link to connect your chain together as the shimano snap off link pins are babber

how are you fixing the chain on ?

Same as always: Park chain tool with a normal HG93 pin.

Get a sram chain or power link to connect your chain together as the shimano snap off link pins are babber

Have used powerlinks in the past (inc the one that broke Sat and Mon) so it’s not that.

Have used HG93s for 2-3 years at least and only had one problem since.

+1 for SRAM links, however I’ve never really gotten on well with Shimano chains.

That many occurrences of the problem cannot simply be down to the chain though, there must be something else that’s causing the breakages. Assuming that you’re in a different gear each time the chain has snapped, you might want to check the teeth of your chainrings just in case a bent tooth is forcing the plates out of line.

My XT chain snapped all the time until I started using the proper shimano joining pins. Now it’s solid.
The XT chains seem to have a very low tolerance for being joined harshly or incorrectly. LX and Deore chains, I find, don’t always need the special joining pins and are a lot more forgiving. But I would always use a joining pin or power connector unless an emergency.

I can recommend Connex by Wipperman. Wouldn’t use anything else now.

check the teeth of your chainrings

Small cog was to blame Sat and Mon, then middle cog just now. Teeth are fine – I too thought one might be kicking out but no. Which is why I’m stumped.

What’s also annoying is I fettled on Sun and the whole bike was proper smooth on Mon. And then bang … bang … bang.

Same as always: Park chain tool with a normal HG93 pin

the “proper” loose pin that comes in the box ?

Too many breaks to be bad chains, it’s either the way you put ’em on or yr setup’s wrong (a bent tooth, badly bent hanger or something?)

Is it snapping at the point of joining or elsewhere in the chain?

Shimano chains have to be joined using shimano joining pins. When you push a shimano pin out, it slightly enlarges the holes in the plates, so you have to replace that pin with a slightly larger one. The larger pins are black as opposed to silver, so you can identify where the chain has been split before. If you rejoin using the original pin, the chain will keep snapping.
I would suggest changing to another brand at the next opportunity.

Reinforced pin fitted first. Same as with last chain.

Snapping not at point of original join. Random.

or buy some joining pins

Hmmm… I really don’t have much else to add. I’ve only ever snapped one chain (a SRAM chain) and the attempted repairs to it using a Shimano joining pin pretty much killed it.

My XT chains always wore out very quickly or went rusty if you looked at them strangely, so I’ve switched to KMC and have absolutely no complaints.

Can you post pics of the exploded plates? Maybe if they’re splaying out on one side you might be able to find out where the breaking load is coming from. I assume it’s a full suss frame, the only other thing I can think of is that a wonky bearing is forcing the rear triangle out of alignment and thus placing a shearing force on the chain.

If you have a shadow mech make sure the cable isn’t going into a jockey wheel at any point during the swing (made that mistake)

And are you sure the length is correct?

Yes, length is correct. I even took it off and measured against previous chain. Identical.

New hanger fitted today too as a result of Mon’s break.

Rear mech not out of alignment. Gears shifting fine.

Can hear/feel that bit of hesitancy when under load, but that’s nothing new – have experienced that for years. Would expect a worn chain to break. Not a new one.

PJM1974, I’ll check out the KMC X9-93 9 Speed Chain if it’s the correct replacement for a 9spd HG93. Not going to buy it just now though.

do you do a lot of gearchanging under heavy load ?

xt cassette here with hg93 chain too, using sram powerlink – for last two years – never had a chain snap…..

do you do a lot of gearchanging under heavy load ?

Nope, nothing unusual. I know how to ‘sync’ an under-load change with cadence etc to minimise things like breaks.

What size of rear mech cage do you have?
Is it possible that the whole rear end (mech and or hanger) is out of alignment?

Oh and BTW – there are no issues using SRAM Powerlinks on 9-speed Shimano chains

Am going to dig out a spare powerlink and replace the broken link to see what happens. Back in 5.

I’ve been using KMC chains for a few years now with either the link they come with or a SRAM one and have had no problems with them

KMC chains and shimano chains are the same as KMC make all shimano’s chains

i had a similar problem and it turned out to be the chainrings, despite me checking them several times.

Forgive the pun, but have you really gone over them with a fine tooth comb? It doesn’t take much of a tweak to a tooth on the rings or cassette to put incredible pressure on one link repeatedly.

good luck – and my sympathies. **** chains – archaic technology 😉

KMC chains and shimano chains are the same as KMC make all shimano’s chains

No, they aren’t.

My KMC chain is nickel plated and the links have a different profile to the plates than my XT chain which appears to be unplated.

I can recommend Connex by Wipperman. Wouldn’t use anything else now.

+1

not that I have broken a sram or shimano, but wippermann do last longer and the connex link is ace and less faff when dirty to undo.. (just have to remember to put it up the right way)

them shimano chains are directional, IIRC. my last was, anyway.

No, they aren’t.

My KMC chain is nickel plated and the links have a different profile to the plates than my XT chain which appears to be unplated.

KMC make the chains to shimano spec… which is a different spec to their own design and marketed chains..

MrK 9 speed Shimano chains (which HG93 is) are not directional. It is 10 speed that are.

Hmm, chain (with powerlink) decided not to snap while going up and down the slightly inclining farm track outside. Did skip a few times though. Might risk a ride tomo morning. Any more probs and I’m switched to KMC or something else.

Cheers guys

I now have, in the words of any chinese chip shop owner, “sore finger”.

Ah, a skipping chain… We’re getting somewhere.

Is it skipping in specific gears?

Second, so it seems.

No stiff links anywhere – every single one checked. Turned bike over and skipping is random. No single link causing it.

Had this happen a couple of months back after replacing chain and cassette. Ended up servicing the hub even though couldn’t see anything wrong with it. Continued to skip when bike was upside down, but not when riding. Odd.

You did say that the chainrings were new too. Bugger.

I wish I had something more constructive to offer than plain “gremlins”.

Is it a full Sus bike? If it is the gear cable may be pulled as the suspension is being used.

Yep, Stumpy FS. But wouldn’t a ‘pulled’ gear cable create a consistent problem?

Gremlins. Yep. Looks like my turn to have a visit from them.

I go through about 4 chains a year although 3 of them will be in the winter months. They don’t like icy cassettes it would appear. I’ll never use a 2nd hand powerlink now and I try to spin rather than heave the cranks round but they all snap in the end. I would double check your chain line is right and make sure your chain rings aren’t warped.

I would double check your chain line is right and make sure your chain rings aren’t warped.

Why to people keeping banging on about chainline on multigeared dérailleur bikes?

on a single speed, hub gear or fixie it is an issue, but on dérailleur bikes with large number of sprockets and chainrings it is just not the issue it is on single speed etc. 8-9-10 etc speed chains are highly flexible – they are designed that way if they were not modern dérailleur systems would just not work.

To the OP,

If you have had thiss chain that has been skipping (especially under load), broken a few times and been repair then it is likely that the chain is damaged in lots of places and will keep breaking.

get a new one and cassette. Check that the dérailleurs are set up properly and check the cables are free (do this by disconnecting them and seeing if they are actually free rather than just shifting)… check also for kinks or cables that are damaged or trapped. Don’t rely on thinking because the shifter moves the cable, that the cables are actually ok.

if they are dragging even a little on downshifts (unless you have one of those older reverse action shimano systems) the dérailleur will not be moving the right amount to shift crisply – this is when you get skipping.. and skipping places large stresses on a chain.

Hope that helps
Si

re: the skipping chain. Once upon a time I had this on an old bike and couldn’t work out what it was. It turned out that the cassette lock ring had come slightly loose so the cassette was moving about a little under load. Worth checking.

Chain Length – I was going through chains like nobodies business, turns out I wasn’t running the chain long enough. Not sure of the science behind it but I started running them a bit longer and not had a problem since.