Do I need a new chainring? Here's my setup:


It runs great. But the chain is a little rusty. I measure the chain wear and it looks like about 1/32 of an inch over 12 inches. So not much, right? But chains are cheap so I try a new chain. The new chain "clicks" at the chainring, especially under high torque. I can feel it in the pedals.

I would think I am perhaps due for a new chainring and rear sprocket, but neither appear that worn:




But the new chain "clicks" and that does not inspire confidence under high torque, and is annoying, so I put the rusty chain back on and all is well. What gives?

Possibly relevant: The new chain sat in the its package for at least 12 months. I rode maybe a mile or two with the new chain and the clicking before switching back to the old chain. The old and new chain are both KMC 8 speed chains.
Chainring wear and noises on fixed/singlespeed drivetrains can be a little nebulous and I think by experimenting with switching back to the old chain you've probably diagnosed the issue as well as possible. I wouldn't expect that ring or cog to be exactly worn out either, but if you look at it you can see the contact side of the teeth is worn down visually from the back side.

If your chainline isn't great that could conceivably create a situation where noise is exacerbated, but if the old one isn't doing it then I doubt it's much of a factor.

Given the choice, I tend to put 1/8" singlespeed chains on every kind of singlespeed drivetrain because I think they add a little bit of smoothness and tend to run quieter and last longer, all else equal. There's no issue with putting them on 3/32" parts like yours. But if wear is causing this then it likely wouldn't make a big difference.

If wear is causing the noise, it will subside when the wear state of the chain catches up to the rest of the parts. Personally I hate playing that game and would rather enjoy a quiet bike.