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Need a new chain for a bike I'm repairing, bike is a 2x10 speed road bike, and I have a spare KMC Z7 7-speed chain. According to KMC, Z7 size is 1/2" x 3/32"

The old 10-speed chain is a KMC X10, and according to KMC size is 1/2" x 11/128".

Cassette is a Shimano CS-4600 10-speed (11-25T)

Question is, will this new 7-speed chain work on a 10-speed cassette? Also are QuickLinks compatible between 7-speed and 10-speed?

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    The nominal internal width is the same, however the external width differs, the higher speeds have narrower plates. A lower speed chain with wider plates will foul the adjacent cogs. The other way around works better, you can use a narrower chain on chainrings/cogs designer for fewer speeds. There is a theoretical issue with dropping the chain between the cogs if you push it too far, but you can use for example a 11sp chain with a 10sp drivetrain OK. The other way around, no.
    – Ivan McA
    Sep 2, 2021 at 10:23

2 Answers 2

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will this new 7-speed chain work on a 10-speed cassette?

No.

That's based on my experience with a nine-speed chain shipped by mistake on a 10-speed drive train. That didn't work well - shifting was horrible at best and the chain wouldn't stay seated on some gears. If a nine-speed chain does that, a 7-speed chain will be unusable.

If it even fits through the rear derailleur...

Also are QuickLinks compatible between 7-speed and 10-speed?

No.

If you put a 7-speed quick link on a 10-speed chain, the wider link will interfere with shifting, and if you're lucky that's all it will do. If you just have standard luck, the wider link will catch on something like your rear derailleur cage, rip your rear derailleur right off, toss it into the rear wheel spokes, and break about 1/3 of those spokes, bend/kink about another 1/3 of them, and put gouges into the remaining 1/3 of your rear spokes so if you reuse them they'll fail quickly at the newly-minted stress risers.

And then you'll crash.

A 10-speed quick link won't fit on a 7-speed chain.

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    Sounds like Mr. Henle has a crash story he’s itching to share :)
    – MaplePanda
    Sep 1, 2021 at 1:46
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Additionally, all derailleur bike chain is 1/2" pitch, with a nominal 3/32" width.

The difference in width is much more subtle - https://bicycles.stackexchange.com/a/17065 shows that the differences in width can be less than 0.1mm

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