Chain down, chain down - chain snap, snapped chain, chain break, broken chains

Big dredge.

My new chain has snapped twice in the last 3 days. First time I pulled out a link and sacrificed the lowest gear, today I've just binned the chain. Does anyone know why this might be happening? The chain was not under any crazy torque, just normal relatively slow commuter cycling. It's a 1 x 10 and it looks like everything is nicely lined up. Cross check, 10sp deore rear mech, grx cranks.

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Could it have been a counterfeit chain? They are quite common these days.

I don't think so? It was from bike-discount.de which looks like a reputable website. I've bought things from them in the past and never had a bad experience.

I never checked my chain line, I just assumed it would be fine with a hollowtech II BB and grx cranks as it's often used as a 1x10 setup as far as I can see. Would that even make a difference? It shifts perfectly with little noise so I assume the chain line is ok

Did it have a master link or a joining pin and is it breaking at the join?

No master link, just a normal chain. To be exact it's a Deore CN HG54.
First time it snapped it completely blew apart, pin flew off somewhere.
Today, as you see in the photo, it just seems to have popped open.
I made 100% sure I didn't make some kind of user error with putting the chain back on, because I assumed I might have somehow done this the first time. Now I'm pretty sure I didn't. Also, I've put chains on and off bikes more times than I can remember and I've never experienced a snapped chain before.

Well looking at the photo, nothing has snapped as in broken, one of the links has come away from the pin. I've joined a chain before with the supplied pin and had it come off while riding. In my experience they're very sensitive to being pushed in the exact correct depth and it can look right but still break open.
I will only buy chains with a quick link/master link now and have never had a problem since. Only chains I've ever broken have been Shimano ones with the joining pin.

Yeah snapped is probably the wrong word, popped open maybe.

Hmm so maybe it really is just a case of bad luck and twice the pins looked ok, but weren't?

What happens with a master link when you need to shorten the chain? You still need to take links out though, right?

Yeah, same procedure, you just push a pin out with a chain tool. The only difference is you need to leave the chain with an inner link at both ends rather than one inner, one outer.

so other than user error, is there any other reason this could have come open? It's just weird because after the first time I took extra care, rather than just autopilot.

Just thinking out loud, but are there any bent teeth on the chainring or cassette?

in my case, the only time a chain snapped or popped, was when i purchased one of those ebay better deals for chains. ahead of snapping it also stretched far quicker than expected.

Cranks, cassette and chain all brand new. That's why it's so sad :(

did yours 'snap' or was it like what happened above?

i don't know for sure as it happened on a main road so didn't go and retrieve any missing or snapped bits.

Omg could this be the reason? I always just use the pin that's already in. I had no idea you needed to use a new pin!

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omg that is a bodge to get you home tactic, not how it should be. There should have been a pin on its own in a blue wrapper in the box. use that (next time) or a quick link and make sure the chain is the right way round if it is one of those ones, taller plates at the back.

Ah yeah, that'll be it. They come with a long pin that you push in and snap off the excess

I've always reused pins :O

Jesus I've been doing it wrong forever

Here’s a useful Link
https://www.kmcchain.com/en/series/chain-connector-single-speed
(Sorry)