New forks & play in stanchions – is this normal?

I got a brand new Manitou Marvel 120mm recently, fitted them to the bike with no problem. However from day one I’ve been experiencing a slight “loose headset” clunk: when rocking the bike forward-backwards with the front brake on, when applying the front brake or when lifting the bike a bit and dropping it on the ground… I blamed an old bottom bearing, which I replaced few days ago only to discover that the problem persists…

I checked everything: hub (brand new wheels really), wheel fitting, brake pads play and rotor (one-piece thing, so no play there, plus they wouldn’t make the clunky noise!) – all perfect… Only just yesterday I managed to find that it actually are the stanchions having a bit of play when the fork is fully extended! When rocking the bike the uppers go down about 1-1.5mm and this causes the dodgy sensation. Is this normal? It’s not happening when fork is open and under sag.

It is adjustable to 100mm (the spacer came with the fork) – would reducing the travel sort it?

I have a feeling this is normal with the manitou forks. Both my magnums do it and so does the mattock. They don’t have foam wipers like the Rockshox but use a rubber twin lip seal secured in the upper under the wiper with a circlip. The slot for this seal is a tad wider than it needs to be (assume due to manufacturing tolerances). Stiction between the seal and the stanchion causes the seal to ride up slightly and the “knock” is the circlip hitting the top of the slot as the seal buts up against it.

One of my magnums is worse than the other so I have a feeling its an inherent design “feature” of these forks.

Doing a lower service and using some thick oil / grease on the seal area helps for a bit but as soon as the grease dissappears the knock returns.

Bit annoying

Do you mean it has a top out clunk? Or actual non-telescopic rocking of stanchions vs lowers?

chiefgrooveguru it is a bit of both I’d say, but very likely that the lateral movement is just an illusion. It also happens when the wheel is turned 90° and the bike is being rocked: looking closely on the seals I can see the upper slide in that small distance. And the clunk appears at the end of the extension phase of the movement.

When riding off road none of the clunk can be felt, it’s only on the full extension, as mentioned earlier. And because the fork closes to “proper-concrete-solid-rigid” when braking on my mainly road commute I can experience that a lot…

It’s annoying!

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I still think it’s the seal I mentioned but to rule out top out / bottom out clunk try balancing pos and neg fork travel with forks NOT at full extension.

Invert forks let all the air out completely, pull up to full travel and connect pump. Then pump to say 50psi.

With pump attached you should be able to compress and extend forks and hear the pressure transferring to both pos and neg Chambers. At this stage usually you need to pull up on the leg before disconnecting the pump which sets the travel and balances the air Chambers.

Instead of max extension, set travel halfway and remove the pump. The forks will stay at this position.

Try cycling the forks and see if the clunk is present. If the clunk goes away then this narrows the problem down.

Interesting designs around…

Always news stuff to learn!

A bit of an update…

I did not do exactly what doncorleoni said, but something slightly similar: I released most of the air from the fork (so it reached about 50% sag under its own weight), then I put the bike upside down and pumped the fork few times. I could hear the oil and air getting mental inside, then I put the bike up, inflated the fork, pumped it down few times and… The problem seem to be gone!

However now when the fork is locked (with me sitting on it) the uppers slide into the lowers about 4 mm (previously there was no movement at all), but from there it is a “concrete lockout”. And no “loose headset” sensation. I’ll test it off road tonight! But this is brazzers… I mean bizarre!!!