So I noticed a little over a week ago that some of the gears on Purple Haze, my road bike, were sounding a bit less silent than usual. This generally means that the chain is worn, and a quick measurement with the chain checker showed that it was indeed worn out past spec. This was a bit curious as I could have sworn that I measured it not too long ago and found it well within spec, but I've got a lot of bikes now so it's easy to lose track of these things.
Anyway, I ordered up a new chain, and decided to take a little side-by-side picture of the two together.
The black chain is the new one, and the somewhat dirty, silver-ish chain is the old one. This is after I cut down the new chain to the correct number of links, the exact same number as the old one. Each pair of links is an inch long, so the old chain had managed to stretch by almost half an inch.
Now I say that the chain has stretched, but in fact what happens is that the inner plates of the chain wear away at the pins over time, causing the fit between them to grow more and more sloppy, which effectively lengthens the longitudinal distance between neighbouring outer link sections by a tiny amount. Left unchecked, this uneven link spacing will eventually cause more wear on the cassette and chainrings, so it's really a good idea to keep an eye on this.
Anyway, the other difference, other than not being worn out, is that the new chain is actually not intended for a 2x11 speed road bike. In fact, it's designed for a 1x12 speed mountain bike, being a SRAM XX1 Eagle chain. The reason for this is that the XX1 Eagle chain is one of the longest lasting chains on the market. The original SRAM PC1170 chain has lasted 2,500 miles (almost exactly), and I fully expect this XX1 chain to last 10,000 miles.
That's a lot of worry-free riding.
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