Rockshox coil knocking noise

shock mounts worn?

Have you tried a smear of grease between the coils and the coil perch?

One of my coil shocks is a little noisy occasionally and a very small smear of grease sorts it.

This...the spring can move on the coil perch,give that a shot

Shock mounts look pretty good, no play.

I’ll try some grease, I’ll kick me self if that’s all it needs!

Thanks for the advice, I’ll report back.

As above it sounds like the spring is moving side to side which means it needs a few more turns. Have you measured the sag? That will tell you if 8 turns is too far or not (unless you have the wrong spring for your weight of course).

One other point. At what point do you start counting turns? When the collar touches the spring, when there is no movement or some other point?

As above it sounds like the spring is moving side to side

I think it's more that the spring turns under load and makes the noise that way than it moving side to side.
For preload I lift the back end off the floor and wind the adjuster until it makes contact with the spring and there's no up/down movement then go from there.
If it's still making a noise you can get nylon washers to fit between spring and perch.

A good friend of mine had a recurring knocking issue on her Aeris 160. It eventually transpired it was the shock hardware. She'd been through a couple of sets which, when measured turned out to be not quite to spec and which had then in turn killed the du bushings which caused the knock. Personally I would be surprised if it was either of these:

Pretty sure it’s the spring hitting in the collars.
Or maybe the spring hitting itself?

With enough pre-load to stop the spring moving side to side by hand (usually very little required) there should be no chance of the spring knocking the collar. If the coils are binding, then the spring must be the wrong size.

Coils can vary in diameter (due to wire size) and some are more prone to knocking than others. Wrap some electrical tape in 3 places around the end of the springs so its snug on the base and try it then to see if its just coil rattle. If it is, I can get you some spacers printed to silence it.

After that then most likely damper and it is very unlikely but possible its a 55 coil on a 65 shock.

Ben@Bird

A friend had this on his am9 from new.

As above some bits of rubber/tape did help but it ultimately went away when rockshox replaced his shock under warranty when it went in for service.

So the knock could be internal as well maybe.

You don't want to put anymore than 3 full turns of preload on a coil spring.

Are you sure the knocking isn't the sound of the negative coil spring inside the shock? They have a habit of coming loose and also you can hear them working in the first part of the travel.

I had exact same on some Marzochi forks when the rebound was set too firm relative to compression and i think from a review i read that the rebound is too firm on these. But bird may well have custom tune.

Also, not sure if air / coil internals share some internals but my air shock developed the same sort of knock and the hot dog piston i think it is is known to cause that knock. Bird knew of it and so did TFTuned.

Give em both a call. Both usually super helpful.

As said earlier if preload is set properly I’d be amazed if its the spring moving.

More likely something simple. If it came in gradually then somethings worn…shock mounts / hardwear.

One last thing, when i went to 50t on my hope wheels the free hub used to bang & knock over bumps as the linkage moved, chain slackens slightly then tightens. Spent months chasing it and even sold a bike. Then exact same issue on new build with hope wheels transferred narrowed it to the hub. Frame is Large AM9. Currently running silt wheels and tis silent again.

I tried grease it didn’t improve. The spring seems to have side movement against the collar even with too much preload. Like Ben said it looks like the inner diameter of the spring is slightly larger than the seat of the collar/purch.
I’ll try some electrical tape/poly washer to pad it out? Thanks for the advice.

I had a knocking/creaking noise when I put the same coil shock on my Bird AM9. Turned out to be due to the hardware. I swapped from a bushing to this bearing kit from TF Tuned, no more knocking!

The spring seems to have side movement against the collar even with too much preload

Is it an RS spring?

Yeah RS spring which now has the last spirals wrapped in electric tape, definitely dulled the noise right down to an acceptable volume.
Pretty poor that an RS spring on a RS shock is so out of tolerance, but happy for the cheap work around.