For years I'd thought you used a narrower chain as you go to higher cog counts (since 7- and 8-speed HG clusters are spaced more closely than 6-speeds or APII 7-speeds, and 9- and 10-speeds are said to be tighter still), but now I've come under the impression that ALL derailer systems use a chain that's 3/32" wide! Of course, there are lots of different chains specifically marketed for different cog-count shifting systems ... if they're not different in width, what IS the difference?

The difference IS the width. 5,6, 7, and 8 speed are pretty much the same width. 9 is a little narrower. 10 is a little more narrow than the 9. 11 is a little more narrow than the 10.

Until you get to 10s and 11s all chains are nominally 3/32". But the actual dimensions vary slightly, even though they all fit sprockets with teeth the same width. The difference isn't in the sprocket it inside width, but in the outside width. Starting with going from pins that protruded about 1mm beyond the outer plate, down to flush rivets, then to the plates being slightly thinner, and the tolerance tightened up to squeeze the last little bit of space in an effort to narrow the chain so sprockets could be packed closer.

There's also a difference in construction that one need be aware of. 5 and 6s chains have pins that stick out, but at 7s, they didn't narrow the chain itself but used pins that ended flush with the outer plate. That creates a safety and structural issue, in that there's no room for plates to spread, and it's easy for the plate to come off the end of the shorter pin. They resolved the issue by peening the head over the plate, or into a countersunk recess in the outer plate to lock it in place in a way that structural steel is riveted. It's important because the rivet head is critical, and that's why 7 and more speed chains cannot be closed by simply pushing a bin back the way 5 and 6s chains can.

Not so minor correction.

Discounting minor variations between brands, 5 and 6s chains are the same, 7 and 8s are the same, then 9s, 10s and 11s are progressively narrower.

Thanks FB, I stand corrected.

Can you explain what this means? I recently used a normal chain tool to shorten a "7/8" speed chain in the normal manner, and it acted just like any other chain I've used a chain tool on. (for removal, I obviously use the SRAM-style quick release that came with it)


I'll have to try comparing again against the older chains in my collection, as when I went comparing chains last night my OE six-speed chains (and probably the five-speed chain, if I can find it) appeared to differ from my 8-speed chains only in that the plates weren't contoured.

Cutting the chain isn't a problem, except that the rivet head increases the force necessary to push the pin, and can break some cheaper tools.

But you cannot splice it by pushing the pin back, because there's no way to restore the head on the rivet. Without the head to keep it secure, the plate which is already at the edge of the pin, can walk sideways a bit and fall off under load snapping the chain.

Funky. I'll have to have another look at the pin in the links I removed.


I did have a more-careful look at dedicated 6, 7, and 8-speed chains, and I do see where the 6-speed chain is a little wider as you describe. I also understand why I found another thread talking about chain widths in tenths of millimeters instead of fractions of inches ... I'll have to take some measurements when I get a new battery in my digital caliper.


So I guess the short of it is, always use a chain advertised for at least the number of cogs you're using, and if it comes with a quick-release link, you should use a chain tool only to shorten the chain and not to lengthen it?

You have the basics, chains with flush rivets, (7 or more speed) can be cut but not spliced except with special pins (Shimano, Campy) or connecting links. As for which to use, a too narrow chain can also be a problem, so try to use chains that match the cassette or freewheel's spacing. There is a bit of fudge room, so for example, I've been successfully running narrow 9s chains with my 10s Campy drivetrain.