Chain noise advise

Hi all, bit of advise needed

Got a bird aeris 145 ive had for a while now with some chain noise issues. Theres a somewhay noticeable metallic “clunk” sort of noise that seems to occure under very small but fast compressions i.e hitting a very small pothole on the road or rolling off a curb at high speeds. On bigger impacts where the compression is more constant the bike is fine. Running shimano deore m5100, chain length correct, btension is spot on. Any ideas? 

Sure it isn’t just a hub with poor engagement?

As above. My first guess would be freehub

Freehub is all good. Its a halo supadrive 120 POE which ive recently serviced, new bearings and pawls

Is it the clutch..?
they do need a small adjustment every now and then..

Shimano chain – Is it on the correct way around? the lettering should be pointing outwards (away from the bike).

Clutch is all good, had it all apart a week or so ago after a real grimy ride. Grease in the right spots, running a fairly high tension but not enough to lose and shifting perfomance.

Chain is on the right way.

While im here ill list a few things i think it couod be in hopes anyone has a way of testing / remedy.

– small chain slap/vibration on the bottom of the chainring

– chain knocking against the bottom of the cassette cogs

– something to do with the suspension kinematics? Chain growth/pedal kickback?

I’m probably wrong, but the Aeris 145 is the same frame as a 120b isn’t it? I used to get quite pronounced pedal kickback on m 120 with a Hope Pro4.
I learned to ignore it, tbh!

Its similar, the linkage pivot in the frame is in a slightly different location so i assime this has an effect on the kick back?

Yeah i try to ignire it because im not dropping chains or having any actual performance issues but the noise just keeps grating on me

How hard are your tyres? Are you sure it is chain-related and not something else? Everything that should be tight is done up tight?
Are you sure it is from the rear of the bike?

Well i assume its rear end sort of area. Front wheel hitting the bump produces no noise, rear wheel hits and i get the noise. Did a full bearing swap about a month ago without any effect on the noise.

Any chance it could be a bit of pad rattle? Im running trp DHR evos

Is the cassette loose on the hub, can you rattle it by hand?

Freehub is all good. Its a halo supadrive 120 POE which ive recently serviced, new bearings and pawls

Mine does this occasionally, take the cassette off and check everything is tight in the free hub mine has a habit of loosening

Does it happen when you are in the largest ring on the cassette?

The cassette on my gravel bike is a very heavy NX Eagle. When I stop pedalling and freewheel the cassette still keeps turning a bit so makes the chain slack. You feel it as it happens and get a bit of a knock when you start pedalling again.

The noise still happens in the larger strockets but less so than in the smaller ones. Cassette is tight. Its not the cassette soinning forwards after i stop pedalling, the noise happens freewheeling or under constant pedalling

Chain routed correctly through the rear mech and not rubbing against the tab?

Sounds unlikely from description, but it’s something many of us have done at least once.

Dont worry, made that mistake too many times to not check it haha. Even got a bit of soft velcro onnthe inside of the tab to dampen and noise