How to tell when NW chainring is worn out?

I reckon that's as good a test as any.  How old is it?

Sounds like a tractor when you fit a new chain.

If it does it repeatedly, where it wouldn't normally, that's when I replace them.

@nickc Several years I think. Problem is that it's mainly been ridden in Pennine mud so comparative lack of miles doesn't necessarily reflect the mount of wear.

@cha****ng Aye, will keep an eye on it and if it becomes a habit...

Next stupid question - can I change the chainring without taking the cranks off or am I hoping for too much?

Narrow teeth are shaved to razors.

Edit: hadn't seen your second Q.

If you're on some variety of 4 bolt: maybe, try and see.

If you're on direct mount, you'll def need to take the cranks off.

@nedrapier M8000 11sp four bolt, not direct mount. Suspect it'll be easier with the cranks off but then I'll find out that the BB is goosed...

Out of interest does anyone still use 'XC' chain guides or have they gone the way of the dodo?

Post up a pic - but as above. I buy cheap chainrings and replace them regularly (usually at about 2000km), using old 104bcd cranks precisely because it means I can get them cheap, I can replace them without removing the cranks, and I can fine tune the chainline with spacers.

I've got a 30t Deore chainring with that bolt spacing (96mm asym) and only 57km on it, message me if you're interested.

I still use a wee chain guide, 'tis a teeny thing though more for my peace of mind I reckon.

@montgomery Thanks, but it's a 32 I need; would really prefer a 34 but the frame won't take it...

chain fell off on a cobbled descent this morning despite the clutch being engaged

I'd check the clutch as well

When I was putting the chain back on the clutch was OK...

Normal test for worn chain ring is wrap a new chain around it and then try and pull a link away in the middle, if it won't budge, it's all ok, if you can lift the chain up in the middle so you can see a clean air between the links and teeth, then the chain ring has worn.