So just how do Rockshox forks circulate oil up to the seals+foam rings, exactly?

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So just how do Rockshox forks circulate oil up to the seals+foam rings, exactly?

38 posts & 18 voices | Started 1 year ago by no_eyed_deer | Latest reply from buzz-lightyear

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no_eyed_deer - Member

... or any forks, for that matter?

I don't get it.

On an 'upright' bike:

1) There is a reservoir of fork oil (15ml per leg on my Rebas) held in place by gravity at the bottom of the outer slider thingy

2) There are seals and foam ring bits at the top of the outer slider thingy, which will need some form of lubrication to work properly, presumably provided by said oil

Does the oil magically 'whoosh' up there somehow while riding? (..how does this happen?)

If riding the bike somehow causes this movement of oil, why does the performance of my forks gradually go 'off' during a ride, only to be re-affirmed just as soon as I turn the bike upside down for a bit, thereby forcing oil into the upper bits of the slider?

I removed my foam rings in an ongoing bid to reduce stiction on my probably a-bit-past-their-best stanchions, was this a good idea?

Posted 1 year ago #
wwaswas - Member

oil lubes the seals because it gets sloshed about as the forks move.

removing the foam rings is a really bad idea - the idea is that they provide a 'reservoir' of oil to keep the stanchions lubed so that they don't wear themsleves out on the bushes inside the fork legs and also keep the wipers lubed to stop them causing stiction.

if the foam rings were bad it probably indicates the oil was going off and needed changing.

Posted 1 year ago #
stilltortoise - Member

Was this Paul Turner's thought process before he went off to make Maverick forks?

Posted 1 year ago #
TandemJeremy - Member

you get a bit of splash lubrication maybe, when you turn the bike upside down oil soaks into the foamrings and top bush, the foam rings act as a reservoir.

I prefer open bath forks where you have 150 ml of oil in the bottom of each leg like older 'zocchis - then you get good splash lubrication to the top bush

Posted 1 year ago #
Trimix - Member

Ive taken to leaving the bike upside down now and again to help.

Posted 1 year ago #
clubber - Member

then you get good splash lubrication to the top bush

sniggers.

Posted 1 year ago #
cynic-al - Member

How does any lube get past the bushing?

Posted 1 year ago #
wwaswas - Member

they're normally slotted al, so I guess it gets carried up on the stanchions as they slide up the leg?

Posted 1 year ago #
TandemJeremy - Member

thru the sliding clearance. There is a clearance in the bushing. its not oiltight.

Posted 1 year ago #
cynic-al - Member

A gap big enough for a "splash" to get all the way up and rest in the foam ring?

Posted 1 year ago #
wwaswas - Member

al - oil splashes onto stanchions as they cycle and is carried up fork past the bushes where it splashes about some more.

Posted 1 year ago #
J0N - Member

I wouldn't rely on the lower oil getting to the foam washers, especially if you have the modern two part seal at the top.
Keep the foam topped up with oil. A bit of silicon spray every couple of rides helps kepp things buttery smooth.

Posted 1 year ago #
TandemJeremy - Member

Every fork I ever have had - bicycle and motorcyle . Better with open bath of course when there is more oil to slosh around. with just a small amount of oil it is best to invert the bike to get plenty of oil into the top bush. It is carried into the bush as the stanchion slides thru it.

How else does oil get into the top bush?

This is IMO part of why foxes can get rapid wear - not enough oil to provide decent splash lube

Posted 1 year ago #
cynic-al - Member

How else does oil get into the top bush?

You assume that it always does? How do you know that?

Posted 1 year ago #
wwaswas - Member

How do you know that?

ForkCam?

Posted 1 year ago #
no_eyed_deer - Member

... so the oil has to get past the bushing to get to the foam ring, ergo - the bushing must be lubricated more or less continually. So is the foam ring absolutely necessary? Does it just provide lube for the seals? Wouldn't turning the bike upside down periodically just achieve the same result?

Hmm... nevertheless, I think I might splash out on some new seals and foam rings this weekend and see if that improves things!

Posted 1 year ago #
bullandbladder - Member

Wow, you'd think that fork manufacturers would consider these things before putting them into mass production

Maybe get them serviced occasionally?

Posted 1 year ago #
no_eyed_deer - Member

Oh yeah... I was servicing them regularly, up until a ride after Xmas, when - unknowingly - a load of thick clayey mud and stones got stuck between the fork bridge and stanchion for all of about - oh - 1km and rather efficiently scratched the stanchion to pieces.

Pretty soon after that, the performance of the forks dropped right off, (can't think why?) so I've been 'experimenting' with different arrangements in order to eeek a bit more life out of the forks, knowing that whatever I do won't matter much now that they're knackered anyway.

So far I found that lubing the seals like crazy with 15wt fork oil before a ride and running much lower pressures +ve and -ve seems to make them quite rideable! ...for a bit, anyway.

Anyway, why am I making excuses, christ - I'm being drawn into this stupid STW you-say-this-I-say-that facile nonsense.

I only asked out of interest really, cos it's fun figuring out how stuff works and playing with things.

(Hey look, I'm doing the rolly-eye thing too now!) Whoop! Two can play, etc..

Posted 1 year ago #
wwaswas - Member

rather efficiently scratched the stanchion to pieces

it may have been pertinent to cover this in your first post, before blaming the foam washers for performance trailing off during the course of a ride?

Posted 1 year ago #
TandemJeremy - Member

cynic-al - Member

"!How else does oil get into the top bush?"

You assume that it always does? How do you know that?

Because I have stripped many sets of forks an observed them and I know how bushes work

If the bush was not getting any oil it would wear the stanchion in no time and many forks do not have the foam rings. However they are usually open bath.

Posted 1 year ago #
bigjim - Member

I do wonder if any oil would actually get past the bushes if you didn't ever turn the bike upside down or on its side. One way to test would be to dye the oil in the lowers and soak the foam rings in undyed oil, and see how long it takes for the dye to reach the foam. Certainly the only thing lubing from my foam washers on revs when i've serviced them has been water!

Posted 1 year ago #
TandemJeremy - Member

bigjim - its certainly pretty scanty on forks with just a few ml in the bottom hence the issues with some foxes and the recommendation to invert them

My pikes on the other hand -all the lube oil disappeared. The only place it can go is out thru the bush and seal. so it must be able to get thru the bush

Posted 1 year ago #
cynic-al - Member

If the bush was not getting any oil it would wear the stanchion in no time

Really? There is a seal there.

Why have the foam ring if oil gets up there so easily?

Posted 1 year ago #
TandemJeremy - Member

Al - read what I wrote please

you get a bit of splash lubrication maybe, when you turn the bike upside down oil soaks into the foamrings and top bush, the foam rings act as a reservoir.

If the bush was unlubed it would score the stanchion in no time - there would be nothing to prevent micro seizures. A bush floats on a layer of lube.

Wahat the hell does a seal above the bush have to do with it?

Posted 1 year ago #
retro83 - Member

Actually on RS forks with proper seals* (i.e. older Pikes) the oil seal is below the foam ring - so I think the foam ring is purely to keep the seals/wipers lubed.

*Like this:

Posted 1 year ago #
cynic-al - Member

Seal mitigates the crap getting in. Not all bushings need lube.

How many folk turn their bikes upside down anyway? Is that even in an RS manual?

Posted 1 year ago #
couldashouldawoulda - Member

The oil in my revs definito gets past the bushes. It also gets past the seals and leaves a small trickle of oil down the back of the outers. This happens in use every time since new.

I have to top them up regularly to compensate. And it's not just mine - its a common "problem" (but not really a problem).

I dont know what black magic / voodoo gets the oil to move up - but it does.

Posted 1 year ago #
jamesb - Member

Is it possible that the foam rings are there to stop loss of oil ? ie they are scraping oil off stanchions and also stopping grit come back down into bushes etc. Do not Foxes use a different thicker oil at the bushes and a lighter one for lubeing? Given how soft teh foam rings are anyway having some oil on them won`t affect the friction, it is the tighter harder bushes that need the lubriaction

Posted 1 year ago #
no_eyed_deer - Member

Ha ha! This is brilliant! Nobody actually knows.

It is all magic..

Posted 1 year ago #
simons_nicolai-uk - Member

Is it possible that the foam rings are there to stop loss of oil ? ie they are scraping oil off stanchions and also stopping grit come back down into bushes etc. Do not Foxes use a different thicker oil at the bushes and a lighter one for lubeing? Given how soft teh foam rings are anyway having some oil on them won`t affect the friction, it is the tighter harder bushes that need the lubriaction

Sounds right- foam ring inner faces have been filthy when I've stripped them but the remaining oil in the leg has (appeared) clean. RS and Fox seals are fairly crap - and rely to an extent on the foam rings. Enduro's replacement seals have a (supposedly higher tolerance = more effective) scraper and replace the foam ring with an oil seal. Marzocchi have good seals and oil seals to keep the crap out. The advantage of the Fox/RS method is lower stiction at the expense of shorter service intervals.

Posted 1 year ago #
thisisnotaspoon - Member

There isn't much space in the bottom of a fork, try putting more than the recomended ammount of oil in the lowers and it soon becomes noticable in terms of reduced travel and oil being forced out of the seals.

So presumably at full compression that 15ml of oil gets forced a long way up the fork leg.

Posted 1 year ago #
no_eyed_deer - Member

Okay.. so foam rings are there to catch crap before it reaches the bushes and oil bath. That does kindof make sense! And tallys with my experience of servicing these forks.. And also makes sense why a US / Arizonan webpage on servicing Rebas recommended removing the foam rings for less stiction - given the relative lack of mud in that part of the world.

So basically, I'm running the risk of knackering my already knackered stanchions further for the benifit of, maybe, a little less stiction. I may still treat the forks to some new seals and rings this weekend though, as to be honest most of the stanchion scratches are a fair way above the seals at static, so perhaps they'll just appreciate a little TLC.

Cheers for the discussion!

Posted 1 year ago #
bigjim - Member

Um, doesn't the actual RS service manual say the foam rings are to lubricate the seals and to soak them in oil when fitting, though thats from memory? I wouldnt say they were solely there to catch oil as if they are supposed to be saturated with oil from the start they aren't going to absorb much more.

Though they clearly do catch crud too as mine were manky and full of dirty water rather than oil at service time.

My revs leak oil out the top caps and valves but not out the seals, though seeing as RS only graced them with a ml or two from new there wasn't much to leak anyway.

Posted 1 year ago #
Rockplough - Member

If I remember right from servicing my pikes, there are small vertical gaps in the bushing material to allow oil through.

Posted 1 year ago #
Ax3M4n - Member

I read this in a magazine article and quoting from memory (so go easy on me).

1) For decent forks, the inner tubes (the top part) don't need manually applied oil. The grommet at the top (where the inner goes into the outer) is there to prevent intrusion from outside grit, dirt etc. So the reasoning is thus: don't apply oil to the forks because that attracts and holds dirt and grit - so don't do it, you don't need it.

2) The lubrication between the inner and outer tubes is provided by capilliary action and motion of the inner tube within the sleeve (lower). The foam ring soaks up some of this oil and acts as a mini reservoir. The foam ring itself acts in two ways a) Wipes off excess oil from the inner tube as it rises b) and at the same time, applies the slightest smear of oil to the surface as it rises out through the busing.

I'm not sure that damping oil and lubricating oil within a fork are one and the same. I think they are different and separate. Maybe someone could confirm.

Posted 1 year ago #

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So just how do Rockshox forks circulate oil up to the seals+foam rings, exactly?

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