I have a KMC X10-93 on my hardtail, with SLX 2×10 stuff. Everything was brand new when it went on the bike. I’ve been looking after it, shifting carefully, spinning up most hills, pulling off in lower gear ratios, keeping everything indexed, clean and lubed, avoiding gears with bad chainlines, etc., but in the first 500 miles, the chain has snapped twice and I’ve put ten speed KMC quicklinks in.

The first time I was spinning up a fairly steep hill. The second was yesterday on a really shallow fire road climb. I’d noticed my gears intermittently misbehaving for about half a mile, adjusted at the shifter until they seemed okay, then within another hundred metres or so, bang.

I’m surprised and suspicious, since I got about four thousand not particularly careful miles out of a nine speed setup with two KMC chains before getting rid of my last bike, and no snapping. Is their ten speed stuff particularly fragile in anyone else’s experience, or might this be a warranty claim?

Funny you mention this… Up until 3 months ago i’d never had 10 speed, I had also never snapped a chain either. I now have a sram 1051 cassette and had a sram 1091 chain. I snapped it 3 times in a month! I then bought the cheaper version as I put it down to a duff chain. Same again! Now I have bought a cheap KMC x10-73 and it’s been really great. I hope this one lasts as so far my other 8/9 speed bikes are a lot more reliable!

Hmm. The 93 isn’t even near 75% wear, but I might try the X10-73 since it’s only a tenner or so.

Snapped one link once on one of my KMC X10-93, and just seemed to be a rare one off. Otherwise indestructible. Had SRAM chains before that and used to snap them a lot.

Was it with a zee mech?

Snapped one cos of a faulty mech recently

No, all SLX stuff. This is the rear, and this is the front.

HG81 11-34 cassette, which I made sure of because I’d read the mech doesn’t play nice with 36T while researching for the build, then an SLX double and bash setup at the front. M670 shifters, and I’ve found it’s always shifted well (It stays indexed for much longer than the SRAM X4 did on the last bike).

I wrote the first break off to bad luck or bad technique, but now I’m kind of annoyed, don’t trust the chain, and am a little worried that a new chain might slip.

Zee is essentially a short cage slx

Check the jockey wheels and cage on the mech

Not just 10sp.
My KMC 9sp did exactly the same at 152km old. Brand new chain, brand new rings (XT), brand new cassette (SRAM 991 or XT, forget which), with every single km ridden on essentially road or towpath spec surface. As did that of 2 others I know. But another friend’s KMC seems fine, but is the gold bling looking version, also bought at around the same time.
Are there chinese fakes out there? Or just random bad luck?

running an X8 with no issues with the Zee mech, but I haven’t any experience with the 10sp stuff

If it’s got 10 quicklinks in, I’d be tempted to warranty it, if possible