When do you replace your chain?

[barrkel]

IMO if the rear looks like that, you've probably lost teeth on the front by now.

Personally I'd replace the lot straight away.

If you really want to eke it out further, I'd have a peek under the front sprocket cover and see how it's doing.

But if replacing, replace everything. When chains get longer, they have a different pitch; they don't match the sprockets. They're literally mismatched.
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Bikes: S1000R, SH350; Exes: Vity 125, PS125, YBR125, ER6f, VFR800, Brutale 920, CB600F, SH300x4
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[B5234FT]

So after all the advice in this thread:

Book spec for length is 323mm max accross 20 links (21 pins) and I measured 10 points on the chain all at 21-22mm

There are some links with more resistance than others, but all move freely and none stay kinked under the resting tension of the chain alone.

Adjustment, book says 35-40mm, I had 55 so one full turn of the axle adjusters brought that back to 35 with some travel still left. Did the tracking with string to check and that was fine too.

No missing plates or barrels or any visible damage

Looks straight from rear both above and below the sprocket

Front sprocket is well worn, but no missing teeth

No reason change from loosest to tightest points around the chain, perhaps 5mm change in the sag in the chain on the bottom side.

Grabbing the chain at 3 o'clock on the rear sprocket there is a little side to side play, around half a mm. I can just pull it enough so see through between the chain plates and the sprocket but only just.

So concluding that it was well worn, but within spec and not suffering from any major issues I've cleaned all four faces of the chain and also the sprockets and front sprocket cover and lubed it. Will see how it is for a while.

Cheers for the advice

[recman]

Doesn't sound too bad given it's not a hugely powerful bike but the sprocket is obviously more questionable than the chain.
Smooth gear changes and regular lubing/cleaning will prolong things of course but I'm not entirely sure I'd like to rely on it (sprocket) on a longer commute.

Replace when funds allow for peace of mind.

[Hong Kong Phooey]