Tech Speak: Talking Fork Seals and Lubrication with SRAM and Enduro Bearings

Pike Seals Rock Shox

Suspension forks have come a long way since the early days of elastomers. What started as low tech springs attached to the front of our bikes has evolved into extremely sophisticated suspension systems with damping circuits that rival many higher horsepower pursuits. With every major improvement to the suspension fork, one thing has remained mostly unchanged – the lowly fork seal. Often neglected when it comes time for maintenance, the fork seal can have a big impact on how your suspension fork performs.

Winter time in the US means it’s a good time for some preventative maintenance to get your bike ready for the Spring. We were hoping to learn a little more about the ins and outs of suspension seals and lubrication, so we spoke with both SRAM and Enduro Bearings (they make the blue fork seals) to get the scoop from a large fork manufacturer (who has made one of the smoothest forks we’ve tried, more soon on the Pike) as well as an aftermarket seal maker.

Slide past the break for the story.

fox32redo_500

Bikerumor: First off, what is the main purpose of a fork (or shock) dust wiper or seal

SRAM/RockShox: Dust wipers and seals are used to isolate material to either the inside or the outside of the suspension.

Enduro (Chris Streeter from Real World Cycling): The purpose of a dust wiper is to keep debris out of a fork or shock. The purpose of a seal is to retain lubricant within a fork or shock.

Bikerumor: There has been a lot of talk about the difference between a dust wiper and a seal. Do you consider your design seals or dust wipers? Is there a difference?

SRAM/RockShox: The common vernacular within the bicycle industry is to call both “seals”, which is correct.  A dust wiper is a very specific type of seal designed to keep foreign objects from entering the suspension. Some dust wiper designs incorporate internal sealing properties to keep oil and air inside the fork as well. A “seal” is anything designed to contain an object in its space.  In RockShox product we have both dust wipers and seals in numerous applications.  In Vivid there is a blue dust wiper that you can see and below that there is a seal that holds all the oil in the shock.  On forks we use a combination of technologies depending on the application.  In most cases we have a dust wiper with internal seals. In BoXXer, Lyrik and Totem we use both a pressure seal and a dust wiper.

Enduro: This is a point of confusion.  It is not a case of either or.  EVERY semi-bath or open bath suspension fork requires both a seal and a wiper.  The point of confusion arises because some companies use a COMBINATION single-piece unit and call it a “dust wiper.”  Actually, such a single piece unit is properly called a “wiper/seal,” because it has a seal element at the bottom and a wiper element at the top.  The Enduro approach is to have a dedicated oil seal and a dedicated wiper.  This allows independent tweaking and improvements in material for each separate component. They don’t do the same job, so don’t necessarily benefit from the same materials.

Bikerumor: Along those lines, for some forks seeing oil wick out of the seals is ok, on others it’s not. What is the theory behind the two schools of thought?

SRAM/RockShox: Visual oil wicking out of dust wipers usually means that the wiper has contamination between the wiper and upper tube.  There always is oil on the upper tubes but should not be visible running down the casting.  The one exception to this rule is right after a rebuild.  The first few rides after a rebuild there will be some additional residual oil and grease that will expose itself.

Enduro: It’s never OK for a fork seal to allow lubricant to leak out.  It affects fluid levels and attracts contaminants.  If you look into this, you will find that the major fork manufacturer who used to say “they are supposed to leak for lubrication” has now changed their seals AND their position as to whether or their seals are “supposed to leak.”

Bikerumor: How do you balance the tradeoff between stiction and the tightest seal?

SRAM/RockShox: We strive for the lowest friction possible while passing all of testing requirements for debris exclusion and seal longevity. We are constantly improving by developing new seal materials, geometries and test procedures.

Enduro: That’s the big question.  Lubricant must be retained with the least possible amount of drag imparted to the system.  It requires a combination of angles, proper tension on the sealing lip, materials, etc..  It’s far from over.

FK6654 FK3929

Bikerumor: How are your seals constructed? Do you use a foam ring and why?  

SRAM/RockShox: Generally speaking seals are molded over steel rings and in some cases have springs added around sealing lips to increase the lip pressure. RockShox uses a foam ring to keep a film of oil on the upper tube before it passes through the wiper to reduce friction and as a secondary trap for any foreign material that might have made is way past the dust wiper.

Enduro: Foam rings have been used based on two schools of thought.  As far as I know, RockShox used them first.  They placed the foam ring between the oil seal and the wiper.  The stated purpose of the foam ring was to keep the wiper lubricated for less stiction.  The foam ring would eventually dry up and it was necessary to pry up the wiper and re-lube the foam ring.  If not re-lubed, the dry foam would actually impede performance.  For this reason, and because prying out the wipers can be a hassle, we don’t include foam rings with our RockShox kits.  If your wipers need a bit of lubrication, a better method is to use Finish Line Stanchion Lube, which can be applied from the outside of the fork and does not attract dust the way fork fluid does.

Fox also uses foam rings, but for a different stated purpose.  Fox’s idea is that a foam ring UNDERNEATH the oil seal can help retain fork fluid up near the bushings.  Our feeling on this is that “it can’t hurt,” so why not respect Fox’s position on this?  For this reason, we include foam rings with the Fox kits.

Pike Seals Rock Shox 3

Original 32mm RockShox Pike Seals

 

Bikerumor: What is the proper service interval for your seals?

SRAM/RockShox: Dust wiper service should be performed every fifty hours of riding to remain at an optimal performance level.  Our professional riders get their suspension seals cleaned in much shorter intervals to make sure their suspension is working at it’s best at all times.  A World Cup downhill racer may only do 15 runs between fork seal cleanings.

Enduro: There is no set service interval due to a wide range of riding styles and riding environments.  Generally speaking, if one keeps the stanchion tubes clean and no oil is appearing on the stanchion tubes, the oil is probably in good shape.  However, anyone who rides in wet and muddy conditions on a regular basis should perform and internal inspection regularly (perhaps weekly).  Then, if everything looks OK inside, one may extend the service interval.  As this process is repeated, the intervals may end up quite far apart in some cases.  For those who are easy on their equipment and ride in dry environments, a minimum annual internal inspection is recommended.

Bikerumor: Do you need any special tools to perform seal maintenance?

SRAM/RockShox: Special tools required are large downhill or motocross type tire lever (something to pry the seal out of the casting) and RockShox seal press.

Enduro: As with many things, a great deal of improvising is done by those who perform their own fork maintenance.  For example, an inverted socket can be used as seal press.  While not ideal, it certainly does the job most of the time.  However, a proper seal press tool with as pilot will insure the seal goes in straight and with the least amount of force, which ensures that the seal is not damaged during the installation.  Having a graduated oil syringe with which to measure and inject fork fluid into the casting holes at the bottom of the lower legs certainly makes the job a lot easier.  Also, a spoon-shaped DH tire lever (such as that made by Pedro’s) allows the seals to pried out with very little likelihood of damaging  the inner surface of the seal head.  Certain forks have fixing nuts that are deeply recessed and require either a special socket from the fork manufacturer, or perhaps some custom grinding of a standard socket performed by the mechanic. 

Bikerumor: I know a lot of people that try to eke out a little bit more performance out of their seals by trying to squeeze in lubricant between full services. There are even products out there now specifically designed for that like Finish Line Max Suspension spray. Are these methods effective, advisable?

SRAM/RockShox: It is a good idea to clean your upper tubes and seals externally before each ride.  Adding a little lube to the outside of the seals, then pushing on the suspension can help lift a little more dirt out from the seal.  Wipe off the excess and head out for your ride.  We definitely do not recommend using anything to pry the seal lip away from the sealing surface and trying to dig out any debris.  If you have that much contamination, it is best to pull the suspension apart to clean so you don’t risk damaging the seals or sealing parts.

Enduro: Some fork and seal combinations benefit from lubrication of the stanchion tubes.  Others really don’t seem to need it.  In large measure, this depends upon the coatings used on the stanchion tubes.  Conventional wisdom would say that the smoother the coating, the less stiction.  Conventional wisdom would be wrong.  A highly polished very closed pore surface has no place to hold lubrication and often can be rather sticky.  In addition, on a microscopic level, it also means more surface contact between the stanchion tube and the wiper and seal surfaces.  In this case, Finish Line Stanchion Lube applied periodically can be helpful. 

Pike Seals Rock Shox 2

Bikerumor: What is the easiest and most beneficial way to keep your suspension working properly?

SRAM/RockShox: Keeping the suspension clean before and after each ride and following manufacturer’s service intervals.

Enduro: Use good quality seals and lubricants, keep the stanchion tubes clean, and invert the fork just before riding to pre-lube the bushings.

Bikerumor: Does the quality of the coating/smoothness on the stanchion have anything to do with the seal’s effectiveness?

SRAM/RockShox: Quality and smoothness are not synonymous in the world of surface finishes.  For example if you had a perfectly smooth upper tube, it would lack the ability to hold any lubrication as it moves in and out of the seal.  This would result in the seal friction being insanely high and in many cases result in premature seal wear.  Because of this, the seal and the surface finish need to be designed and tested together to ensure in a variety of conditions they preform as intended.  Just changing the surface finish does not mean you will get an increase in sealing performance.  For example the BlackGold upper tube finish we used in BlackBox had less friction than our standard anodized upper-tube, but preformed the same in terms of sealing.

Enduro: As previously mentioned, A highly polished very closed pore surface has no place to hold lubrication and often can be rather sticky.  In addition, on a microscopic level, it also means more surface contact between the stanchion tube and the wiper and seal surfaces.  However, to the naked eye, a stanchion coating that looks very smooth may, in fact, have a relatively rough surface when under a microscope.  If these irregularities are not large enough to allow fluid to leak, but do allow enough to penetrate the surface and provide lubrication, the result will be less stiction.  Surface coating materials for optimum performance is a science of its own.

LU6519

Bikerumor: How do you lubricate the internals of the shock – is it open bath, closed bath, grease, etc?

SRAM/RockShox: All RockShox must use RockShox service kits and RockShox suspension oil only.  The reason for this is that seal materials react differently to different lubrications, sometimes resulting in seal swelling or shrinking.  At RockShox we specifically design and test the compatibility of our sealing materials with the lubricants we use.  We have seen many cases where other lubricants are used and the seals shrink resulting in leaking.

Enduro: We make aftermarket seals for forks and shocks. We do not currently have a line of forks or shocks of our own.

Bikerumor: Do you use a special grease for your bushings?

SRAM/RockShox: RockShox bushings are lubed with the oil bath in the casting, we do not recommend the use of grease on our bushings.

Enduro:Most forks on the market today are open bath or semi-bath, meaning the bushings are lubricated by fork fluid.  I am aware of one brand that has gone back to grease lubing, but, in my opinion, it is only due to a failure to produce a satisfactory oil seal for their product.  Grease lubed forks went away for a reason.

 

Comments

dennis - 12/04/13 - 12:57pm

What is the consensus on storing your bike upside down (i.e. hanging from the garage ceiling)? Does this ultimately help by keeping the foam rings wetted?

I’ve checked the manual for my new Pike but didn’t find this mentioned, nor did I see it in the manual for my previous Fox 34.

LULZ - 12/04/13 - 12:58pm

Nice work Bikerumor! This was an excellent read. Keep up the great work.

John - 12/04/13 - 1:07pm

@Dennis: Yes, it’ll keep it more “wetted”. I personally haven’t seen Rockshox say to flip the fork over, but I do remember reading Fox saying to do that. When you think about it, if you keep a fork vertical, the oil will slowly seep downwards. Flipping it will put that oil of the foam rings. Presto!

Great read! I find it interesting the difference in wording, but overall the similarities between the two companies on their sealing. Can anyone comment on the seal press to use for the Enduro wiper/seals? I know they have longer, tapered wipers as compared to say Fox or Rockshox.

groghunter - 12/04/13 - 2:05pm

keep in mind, however, that storing your bike upside down can adversely affect other components. Hydraulic brakes don’t like it: you’re moving the air bubble in the reservoir into a position where it can contaminate the fluid in the lines. also, because of the propensity of MTB to utilize conventional forks instead of Upside-down, you often have a catch-22 here: storing the bike in a way that keeps oil in contact with the fork seals moves the oil away from the rear shock seal, and vice versa. I’d rather take apart a fork than a shock, so I’ll live with possibly decreased life on fork seals to gain life on shock seals. OR just go with a USD fork, since we’re finally seeing them again.

ChrisW - 12/04/13 - 3:22pm

What is the current wisdom on fork boots – do they help to keep dirt away from the stanchions, or are they actually just trapping stuff in there?

groghunter - 12/04/13 - 3:43pm

modern thought process is that they trap stuff, and that modern seals work well enough to not need them. However, I just got a shock back from Rockshox, who told me to wipe the shock down after each ride, because the air can was full of dust. So obviously, something isn’t working right there. and wiping the shock down after a ride doesn’t address the dust that’s getting on it during the entire ride, so sounds like a suspect fix.

Dan E - 12/04/13 - 8:14pm

Here’s what has changed:

Older forks, although not as high-performance, were bullet-proof.

Seems like the more we try to convince ourselves that all the technology results in better performance, the closer we get to “Jaguar” maintenance requirements.

Just got told that my Brain Fork needs to be completely serviced every 30 hours of riding…in So Cal where riding trails is as perfect a fork-life environment can be…and 90 hours before it has to be sent into the factory. Anyone else frustrated that for every month of riding, you spend several hours servicing and you lose your fork every three months for a month for a rebuild?

My Judy DH may not be the greatest, but at least it works, flawlessly, for the last 15 years.

Jeb - 12/04/13 - 9:35pm

@Dan E You lost the plot at “Brain Fork”. “Brain” is Specialized code for “this thing sucks and will fail quickly” I have a Rock Shox Revelation that is 3 years old, gets a seal re-build and oil change every year (at $20.00 a pop for the kit, I do the work) and regular seal lube and still rides like new.

greg - 12/04/13 - 10:31pm

brain systems are quite reliable, and happen to perform awesomely.
@groghunter:
rear shocks are oriented differently on different bikes, making it difficult to distinguish what is up and what is down. also, their “bushings” dont pass oil from one side to the other.
as for brakes, if you have air in your reservoir, you should get the air out. brakes should be able to handle being upside-down, or something is wrong.

goridebikes - 12/04/13 - 11:47pm

Dan E,
if changing the wipers / seals and oil in the stanchions takes anything over about an hour, yourself / your mechanic should cease working on it, and find someone slightly more experienced.
It’s a very quick, very easy thing to do – remove lowers, remove seals, clean uppers, clean lowers, install seals, install lowers. Ride.
FWIW, 30-60 hours is ideal for almost every customer I’ve worked with, and the ones who come in once a year only are the ones I end up turning away after 2 years because the stanchions are scratched and there’s no point in changing seals and oil in something that leaks them out after 2 rides.

John - 12/05/13 - 12:05am

@groghunter: Actually, from what I seen, flipping the bike shouldn’t been an issue. A properly bled brake system will not have air in the reservoir, and will use a rubber bladder to expand and contrast to compensate for the fluid’s changes in temperature, pressure, etc, etc (note a little hole on reservoir caps for movement of the bladder on some brakes). So, flipping the bike over shouldn’t do anything as the air bubble in the line will work itself upwards into the reservoir. If you have enough of an air bubble for the brakes to go soft when flipped, you should get your brakes bled regardless. Half the reason I see people not liking a certain brake system is because it’s not bleed properly, and the pads aren’t bedded in properly.

As for the rear shock, if you have ever seen the inside, you’ll see little white rings next to a rubber “quad” seals. These white rings are teflon rings, and are self lubricating in their nature. Even then, with the amount of oil inside the rear shock, and the viscosity of it doesn’t really do much if you flip it. Rockshox states 0.3ml of 15w50 and Fox 5ml Float Fluid, both of which are viscous. The oil doesn’t really “pool” that well like in the fork.

MrDoom - 12/05/13 - 9:26am

I don’t think the older forks were “bullet-proof”, my Mag-21 and Manitou mach 5′s were high maintenance units and blew through seals and bushings far more quickly than my Pike which after eight years has only had a few oil changes and developed a creak in the crown before it needed seals or bushings. (It was stored hanging by the front wheel BTW.)

Of course it depends on the conditions and type of dirt/dust you ride in, I think the manufactures assume a worst case scenario when calculating how long you should go between servicing a fork and since I ride a rigid SS in the muck of winter my suspension forks don’t get worked over by the elements.

groghunter - 12/05/13 - 11:13am

Guys,

While I understand what you’re saying, brake reservoirs are designed to be a collection point for air in the system. sure, in an ideal world, there is little to no air in the system, however, in the real world, people ignore service intervals in favor of “it’s still working, doesn’t need maintenance.” So brake manufacturers build a method for the system purge air from the hydraulic circuit, which is to allow gravity to push it up to the reservoir, where it collects at the top, out of the normal hydraulic cycle. You may feel fine gambling on someone knowing enough about their bike that they won’t let their brakes go badly enough to cause a problem, but personally, I’m at least going to inform them about the risks.

Secondly, some specific brake models are notorious for pulling air past sealing elements in the system, or allowing it to creep in. So unless you bleed these brakes every few weeks, there is always some air in those systems.

Put simply, there’s a reason why, at a certain bike manufacturers new model year event for their dealers, when they asked if there were any issues or problems that dealers had been having, the entire room stood up and said “no more avid brakes, please.”

ed - 12/05/13 - 11:21am

Great article! Keep up the awesome website BR!

patrik - 12/05/13 - 2:01pm

@Dan E: You should know what you’re getting into before you a buy a “BMW.” Sounds like you’re more of a “Camry” guy.

If you did your homework, you would have known before purchase that high-end components require high-end maintenance. Woe is the customer who moans and gripes that his components aren’t working correctly, when he answers the question “When was the last time you serviced your widget?” with a “Huh?”

It baffles me why people go to Jiffy Lube religiously every 3,000 miles for their car, yet jump up and down like little girls when told that their bike needs service. Higher-end cars have more stringent maintenance requirements, but it’s different for bikes? I don’t get it.

Take any other hydraulic device, pump it up and down for 30 hours, and tell me that it wouldn’t need service. Why is a bike fork any different?

groghunter - 12/05/13 - 2:29pm

patrik,

I think part of the problem is that if you contrast a Fox (let’s be real, that’s who we’re talking about) with an open bath fork, the service intervals seem far too often. look at how long you can go with zero maintenance on a inverted open bath fork, and it looks positively obscene.

While it is in service of a lighter weight, many would argue that costs outweigh the benefits, or that Fox’s strategies for keeping the seals lubricated function poorly, requiring excessive maintenance, and that the damage that can occur if maintenance isn’t done is far too severe for such an expensive part.

Ed - 12/06/13 - 11:40am

Can’t recommend Enduro seals for riders who aren’t diligent with maintenance. (Yes yes you can argue that’s the rider’s fault and technically without maintenance some sort of failure should be expected etc.) My experience has been that the Enduros wear the anodizing off of the stanchions in similar conditions/circumstances when uppers with oem seals are fine. I’ve talked to others who’ve had similar experiences with these as well. Wondering if anyone here has noticed this?

Chris Streeter - 12/06/13 - 2:15pm

Hey, Ed: Stanchion wear is always due to one of two things (or a combination of both):

1) Lack of lubrication at the bushing, causing metal to metal wear.
a) Due to not keeping oil level up
or
b) Due to wrong tolerance between bushing and stanchion tube

2) Ingress of contaminants that get trapped and act as an abrasive.

Seals are not capable of wearing the hardened coating. If they were, when stanchion damage occurred, it would run the entire contact point of the seals. It never does. It always shows up on the fork where the stanchions are at the greatest friction point with the bushings. Very often, all the damage is in fact below the seal level, where the seals have never even contacted the tubes.

If a fork is built with the right tolerance between the stanchion tube and the bushings, and the proper amount of lube is contained in the lower leg, hydrodynamic lubrication takes place, which simply means a layer of lube is maintained between the bushing and the tube. If this layer goes away, metal on metal wear takes place.

Maintaining lube levels, keeping the fork clean, and a quick tilt back on the rear wheel to pre-lube the bushings at the beginning of a ride will prevent this damage as long as the manufacturer has done his part (proper bushing to stanchion fit, properly applied stanchion coating).

Dave - 02/22/14 - 11:31am

The NEW Fox fork seals are SKF and are really good seals, I send my fork and shock off too Suspension Experts every spring. That’s all they do in MTB, PUSH is another company that really knows what their doing. You will feel the difference a good tune makes !!

Tim - 04/16/14 - 12:56pm

Any feed back on using silicone vs teflon stanchion lubes, or other lube fluids?

Chris Streeter - 08/30/14 - 7:56pm

Dave, sorry to be so late in responding. Regarding what lubes to use on the stanchions, I’d start by saying any lubes used inside a fork don’t do well on the outside. They usually attract dust in all the wrong places. Even lubes meant for the outside, if in spray form, have to be applied carefully so that overspray doesn’t “lube” the brakes or attract dirt to other parts of the bike. Some sprays also use different “carriers,” so a “silicone spray” may not be 100% silicone and the additives may affect the wiper material. For this reason, I think it’s best to use something designed specifically for the job.

Just want to reiterate the general principles regarding stanchion lubrication that I stated above in the article:
Some fork and seal combinations benefit from lubrication of the stanchion tubes. Others really don’t seem to need it. In large measure, this depends upon the coatings used on the stanchion tubes. Conventional wisdom would say that the smoother the coating, the less stiction. Conventional wisdom would be wrong. A highly polished very closed pore surface has no place to hold lubrication and often can be rather sticky. In addition, on a microscopic level, it also means more surface contact between the stanchion tube and the wiper and seal surfaces. In this case, Finish Line Stanchion Lube applied periodically can be helpful.

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