[Verskis]

Does it matter if there were more lubrication oil than recommended on the spring side of a 35mm Boxxer fork? I guess the spring chamber isn't sealed in any way, so in full compression all the extra oil would go into the spring chamber, right? Or would this cause too much resistance, causing unwanted extra compression damping at the end of the stroke?

The second question is, are the Boxxer seals incompatible with Red Line oils? I installed an Avalanche cartridge to my fork, converting the damping side to an open oil bath (=the same oil for damping and lubrication). I filled the damping leg with yellow (Light) Red Line suspension oil. At first it worked fine, but after a week and a half there is definitely more stiction in the fork, just like the seals have been swollen or not lubricated well enough. Anybody else had this kind of issue with Red Line oils?

 

[HardtailHack]

The extra oil on the spring side should be fine.

I run Redline 2.5 in my Totem and it seems fine however I seem to go through quite a lot of grease on a service. I grease the stanchions and instal them rip them out and repeat that a few times then throw some more grease on the bushings and slap em all together.

I found with the Totem if you are at all sparing with the grease they get a notchy stictiony feel very quick, also Slickoleum or Slick Honey is the best stuf to use, magic stuff.

 

[Udi]

This is a topic I've had great interest in, so I might be able to help.

I've noticed a correlation between high-VI oils (such as Silkolene, Redline is another very likely possibility) and increased bushing stiction. These two oils are by far the highest VI oils you can buy, and work great in dampers, however they are NOT the right choice for lubricating lower legs and bushings in my opinion.

The stiction isn't to do with the oils frictional properties, rather these oils seem to have the ability to swell the PTFE bushing coating ever so slightly - I've noticed this primarily in RS forks, so perhaps their material is more sensitive to it. I don't think it's a direct result of the high VI, perhaps rather a side effect of a VI increasing additive used in these oils.

Once this happens it's not actually reversible, short of re-sizing the bushings (there are tools to do this, some a little unorthodox - but it's not the end of the world). To check if this is the problem, you can remove the seals from the fork and cycle the stanchion through the bushings by hand without lubrication. I tested this over several forks including brand new ones before/after an oil change. It took me a while to figure it out because it seemed so unlikely.

The great thing about semi-bath forks is that you can use separate oils for damping and lubrication, this is something Fox has taken advantage of (RED damper fluid is Silkolene RSF, GREEN fluid is a proprietary bushing lubrication oil). Thankfully, anyone with a semi-bath fork can do the same thing.

My findings seem to be backed up by a moto suspension guy under the username PMK on MTBR, and it was the first time I had seen my suspicions/results duplicated. Hopefully this information will be useful to someone else.

The bottom line here is, if you're particular about stiction, don't stray from the manufacturer's recommendations on bushing lube oil unless you know it's a safe product. Thus, Torco RFF (or RS fork oil) is safe in RS lowers, and Fox GREEN works brilliantly in Fox lowers. I'd hazard a guess the GREEN will be good for RS too and will try it myself sometime.

 

[Udi]

Also, as HardtailHack said, extra oil in the spring side is fine. Basically the only limitation to how much oil you can run is the total internal volume at bottom out - so more volume = more oil capacity before the seals will get pushed out under pressure.

 

[tacubaya]

UDI:

Fox Green is brillant as well on RS lowers.

Right now I have several containers filled with different oils and with an oil seal and o-ring submerged. I measured them before submerging and will be left alone for a couple of weeks to see which oil swells them up.

Right now I am testing:

Mobil Vactra 2 (smoothest lubrication oil i've seen) - VI 96
Mobil 80w90 Gear Oil - VI 103
Silkolene RSF 10 wt (Fox Red) - VI 303

These are going next:
Mobil 1 ATF - VI 176
Motor oil (probably Mobil 1 or Castrol Syntec 10w30) -VI 146

 

[Verskis]

Alright, so I have to resize or replace the damping leg bushings if they are swollen? Will they not get worn to perfect size after a while if I change the Red Line oil to some other oil?

 

[Udi]

Verskis -
Yeah don't replace them, bushing replacements in RS forks don't always go well. Change the oil to something you know is good, and see how it goes after some riding time.

Tacubaya -
The issue there is, the rubber seals / nitrile o-rings won't really indicate the effects on the PTFE coated bushings, and in my experience that is the part that causes the stiction. Personally I haven't noticed any ill effects on seals with any of the oils I have used, at least not enough to cause differences in operation.

 

[HardtailHack]

Hmmm I can't really comment on the Redline oil swelling the bushes, the last time I reassembled the forks I polished the bejesus out of the stanchions as the damper side didn't look great. But anyway with 2.5wt Redline my fork feels better than it ever has in both the damping and stiction department so I am fairly happy, it's still a crap for but it feels better than it did when new.

How does Udi only have four rep points?

 

[Sandwich]

To udi's point,
I had the same thing happen on my 2010 boxxer. It developed terrible stiction to the point that no low speed compression damping was the only way to ride. I used motor oil, which a lot of people will tell you is fine, but it's simply not, and I believe it has something to do with what Udi is saying.

Rockshox replaced my fork in its entirety and the problem went away, and from then on I used only RS brand lubes. I did regularly use extra oil in the spring side on the original fork, since I was desperate to get it to work, but it didn't seem to help nor hurt.

To this day I don't know if it was the motor oil I used, or something the PO did before me, but it was clear that something was mechanically not right, and I'm willing to bet it was bushing swell since the problem didn't appear with seals removed or dampers detached. I'm happy RS replaced my fork, but in the future I'm less apt to buy another one, as seal swell combined with misaligned lowers and a feel that was just never that impressive will steer me towards another manufacturers product.

 

[Verskis]

Verskis -
Yeah don't replace them, bushing replacements in RS forks don't always go well. Change the oil to something you know is good, and see how it goes after some riding time.

I will do that, thanks for the help! But what do you mean with bushing replacements not going well?


HardtailHack:
Do you use the Red Line oil in the damper only, or also as a lubrication oil on your Totem?

 

[Verskis]

I'm willing to bet it was bushing swell since the problem didn't appear with seals removed or dampers detached.

But then it cannot be swollen bushing, if there were no stiction problems when you removed only seals or damper, but left the bushings untouched.

 

[Sandwich]

Sorry, I mis-phrased that, the problem REMAINED when the seals were removed and the damper was loosened/spring side only was used.

 

[Verskis]

Okay, now it makes sense.

 

[tacubaya]

Verskis -
Yeah don't replace them, bushing replacements in RS forks don't always go well. Change the oil to something you know is good, and see how it goes after some riding time.

Tacubaya -
The issue there is, the rubber seals / nitrile o-rings won't really indicate the effects on the PTFE coated bushings, and in my experience that is the part that causes the stiction. Personally I haven't noticed any ill effects on seals with any of the oils I have used, at least not enough to cause differences in operation.

Yeah I know. I wish I had spare bushings and the correct measuring equipment to test them out. All I can do for now is test the seals and o-rings for swelling, degradation or significant change in durometer.

 

[baca262]

there are very few things that can make ptfe (since it's VERY chemically inert) swell and i don't think motor oil contains any of them. the oil and dust seals are a completely different story. if you use motor oil in the lowers, make sure it's fully synthetic, non synthetics make seals swell. also, 5w synthetic car engine oil =~ 15w shock oil viscosity wise. i've always used it in my old rs pike and never caused any harm.

so, replacing the seals and lubrication oil might just be the ticket to get rid of the stiction

 

[HardtailHack]

You can get additives to make PTFE swell but in ordinary engine oil you'd think the only thing that may do it is the detergents in the oil.

Verksis, I run 20WT in the lowers.

 

[Udi]

I will do that, thanks for the help! But what do you mean with bushing replacements not going well?

RS forks just don't seem to take kindly to bushing replacements, I think in most cases the entire lower leg is replaced (for warranties etc, at least that I've seen). If things don't line up exactly, it will wear gouges into the stanchion. Not something I would recommend doing yourself.

In any case, I think if you clean out the fork, use the factory oil, and give it some riding time you might be just fine. If it's not, I'd just resize the existing bushings - TF tuned have a tool that they bang into the fork to do this, and I think most SRAM distributors may also. You can also DIY in a number of ways carefully - varying grades of sandpaper on a broom handle (end with wet and dry), engine cylinder honing tools, etc. Sounds a bit dodgy but works well if executed correctly. Keeping in mind you are just thinning the polymer bushing coating, NOT removing it (metal on metal = bye bye stanchion).

there are very few things that can make ptfe (since it's VERY chemically inert) swell and i don't think motor oil contains any of them. the oil and dust seals are a completely different story. if you use motor oil in the lowers, make sure it's fully synthetic, non synthetics make seals swell. also, 5w synthetic car engine oil =~ 15w shock oil viscosity wise. i've always used it in my old rs pike and never caused any harm.

Too many generalisations.

1. No one really knows the exact formulation of the bushing coating on a fork, it's obviously some sort of polymer, but I just stated PTFE as a close guess. I'm fairly confident that it varies from brand to brand, and perhaps even fork to fork in some circumstances. I did notice that for a given lube, a Pike wouldn't get sticky where a Boxxer would.

2. Synthetic can mean a myriad of different things when it comes to vehicle engine oils, and I can guarantee that no matter what you use, there's a variety of additives (a lot of which won't be labelled or disclosed) - any of which could affect bushings or seals. There are extreme-pressure/wear prevention additives, detergents, viscosity modifiers, viscosity index enhancers, and many many more.

The same applies to any oil really, which is why I think it pays to be careful.

 

[baca262]

i agree with everything you've written udi but i'd like to add that the default answer to a rs lubrication question on dropbike.com (the only one truly active croatian mtb forum) is fully synthetic motor oil and in 4 years i've been active there i've never seen anyone having any parts swelling (using random brand oils, that is). this is because we're very low on $$, well, the most of us is and have to mess around to make everything as cheap as possible + getting all the original stuff is nothing short of nightmare around these parts.

 

[Sandwich]

FWIW I used Mobil one 10w40, I think, in my ruined fork. Of course, this was the notched casting, very early 2010 edition....but it was still garbage.

Shock oil is going to be relatively additive free and that's what you want in a shock. It's worth the extra $10 a pint.

 

[Verskis]

I drained the Red Line oil out of the fork, and cleaned the fork pretty well. After that I filled the damping leg with Motul Factory Line oil, and the stiction issue was almost gone. I think the fork is not quite as smooth as before, but it is quite close. I suppose some more riding time will fix that.

I did not take the seals out to test if it definitely are the bushings that are to blame, but at least it was not the damper. I pushed an empty stanchion back and forth in the lower legs and it felt as bad as with the damper on.

 

[Udi]

That is good to hear. Let us know after some ride time if the stiction comes back or stays away.

My experiences with using the wrong oil were very similar to you and Sandwich, which is why I suspect it was the same issue. One to two weeks after a rebuild the fork would just feel very sticky, and it would feel like there was more damping when it was actually just more stiction.

It wasn't *terrible*, which is probably why more people don't complain about it - or they just rebuild more often, which was my solution until I figured out what was happening.

 

[tacubaya]

Results:

Mobil Vactra 2: no swelling
Silkolene RSF: no swelling
Mobil 80w90 gear oil: no swelling

They were left submerged in each fluid for 3 weeks.