The Tuesday Tune Ep 10: What's in Your Oil? - Video

Jan 10, 2017
by Vorsprung Suspension  
Views: 3,062    Faves: 20    Comments: 0


This week on the Tuesday Tune we're delving into suspension fluids to discuss some of the demands placed on them and how the manufacturers develop the properties that are necessary to meet these demands. Since we at Vorsprung Suspension aren't chemists, we invited Alex Marangoni, Canada Research Chair, Professor of Soft Material Sciences at the University of Guelph and the scientist behind Whistler Performance Lubricants to explain a few things to us:
1. What the major demands on suspension fluids typically involve
2. What base oil types are used and their properties
3. Some of the compromises involved in oil design
4. How oil properties change with temperature and over time

From the workshop's point of view for servicing, we consider three main factors in the most relevant priority order when selecting an oil for a given application:
1. Viscosity - how thick the oil is, and its resistance to flow through shear
2. Viscosity Index - the thermal stability of the oil and ability to minimise changes in viscosity as temperature changes
3. Lubricity - its ability to reduce friction.

Each of these factors has to be considered in terms of its relevance to the oil's application. For example, fork splash bath lubricant needs to lubricate first and foremost, and forks in general are more sensitive to stiction than rear shocks as the rear shock has the leverage of the suspension linkage to help overcome its friction. Conversely, rear shocks see more heat than forks, so thermal stability becomes a bigger concern.

Following those three primary considerations are secondary considerations, in no particular order:
1. Oil durability - oil breakdown through thermal and shear stress occurs over time.
2. Environmental concerns (side note - WPL's oils are biodegradable and non-toxic... but they taste terrible and eating or cooking with them is still generally not recommended)
3. Price
4. Anti-foaming characteristics (for open bath/emulsion dampers only)
5. Other factors affecting performance such as adhesive additives ("tackifiers") that can drag oil past seals

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55 Comments

  • + 9
 Just awesome. You have an uncanny ability to answer the questions that come up from week to week. Thank you again for this series!
  • + 5
 Thank you for making these videos and providing the opportunity to better understand suspension. What was previously voodoo is slowly becoming slightly less voodoo as each video is released. Keep 'em coming.
  • + 3
 Are forks recomended oil levels for the best performance possible, or a balance between weight and performance? For example, the dvo emerald uses nearly twice the oil of a boxxer or fox40. Would more oil benefit the performance of a boxxer/40, or is due to the different fork designs?
  • + 7
 That particular case is more to do with the fact that the Emerald's damper is open bath - these always require a lot more oil than sealed cartridge dampers like the Boxxer and 40 use. In many cases there are limitations on how much oil you can physically fit in the fork lowers before the fork would have issues with hydraulic lock, or at the very least excessive pressure build up. Any forks where the bottom of the stanchion is sealed off for any reason will run relatively little oil in the lowers.
  • + 2
 @VorsprungSuspension: Hi Steve, can you recommend the best 85/150 5wt open bath damper cartridge fluid - can anything beat Golden Spectro...not seeing a lot of info online talking about this and as you state, not all fork oils are the same? Also, along the line of what's being asked above...how might residual OEM oil impact oil characteristics when switching in a damper (closed --> open bath)? Thanks
  • + 3
 You did not mention anything about compatibility between the suspension fluid and the other components of the forks, I am mainly thinking about seals, gaskets and bushings here. Is there a risk of compatibility issue or is this a kind of urban legend to keep you from buying something else than the oils recommended by the manufacturer?
  • + 8
 Alex here....so, here comes the geeky answer. There is a parameter the scientists like Hildebrand and Hansen developed which characterizes the "chemical nature" of a polymer (elastomer). They were interested in predicting if a certain polymer was soluble in a particular solvent. The treatment is not difficult and it comes down to "like dissolves like". Like water does not dissolve oil but a mineral spirit does. So, if the chemical nature of the solvent is similar to the polymer....wham....it starts swelling and eventually dissolving, losing tensile strength, going to hell. What you could also do is washing out "plasticizers" which are added to the polymer to make them nice and soft and then your seals turns hard as a rock......not good.

So, here it comes....if the absolute difference in HIldebrand solubility parameter between the polymer (elastomer) and the solvent (suspension oil) is greater than 2, then they are compatible. This is based on experience and testing.

Now, which elastomer you say. Let's assume that all seals are made of NBR (Nitrile butadiene rubber under trade names such as Nipol, Krynac and Europrene), there is NO PROBLEM AT ALL since this elastomer has a solubility parameter of greater than 20, while WPL oils have a solubility parameter of about 15-17. So, we are all good. Having said this, let's pay tribute to mineral oils and PAOs which have Hildebrand Solubility paramters around ~10.

However, this analysis will depend on the type of polymer that you use....natural rubber (NR), styrene-butadiene rubber (SBR), epoxidized natural rubber (ENR), ethylene propylene diene monomer (M-class) (EPDM). You could just look up the value of the respective polymers and judge by yourself (all in interenet). But I think most manufacturers are using nitrile rubber, so, we can pretty much be cool about the whole thing. If we are talking about natural rubber....then we may have problems.

Does this help?
  • + 1
 There is always that risk if you're using oils that aren't designed for the task you're using them for. Lots of engine oils, for example, have detergents and seal-swelling additives that can mess with some of that stuff. Suspension oils often contain seal conditioning agents that help keep them soft and lubricated rather than swelling up or cracking.
  • + 1
 @amarango: yes it does, thanks! I feel kind of lucky that I studied material science back in the days! Wink

Next question would be what is made of what in a fork?

Orings are most likely NBR as you mention. Bushings seems to be made of PTFE. Dust seals from SKF (or Fox, RS and racing Bro) are made of NBR.
PTFE has a Hildebrand parameter of 6.2 which is then close to mineral oils and PAOs. But maybe 6.2 to 10 is enough? And maybe these 2 are not so common in suspension fluids?

What about the other components of the suspension oil like detergents, tackifier, VI improver, lubricants, etc...? Would they have similar Hildebrand parameters as NBR or PTFE?
  • + 1
 @VorsprungSuspension: thanks for answering while I was replying to Alex!
It sounds like as long as I use fork oil in the right place (damper oil in the damper with the appropriate viscosity and lubrication oil in the lower legs) I can use any brands I have available.
  • + 1
 @Happymtbfr: Are bushings made from PTFE? When I looked at the bushings in my forks (Magura) I just thought these were made from POM. POM has a good chemical resistance (also used in cigarette lighters) and good lubrication (used as gears in kitchen appliances etc)so it thought that was a fair guess. But I didn't even think of PTFE. Then again I don't even know what PTFE looks like. My bushings are white. Teflon tape used for gas fittings in plumbing is white too but teflon in pans for cooking is black. Or does bushing material just vary a lot between brands?
  • + 4
 @Happymtbfr: Great to meet a materials science bro. Now that you mention it, mineral and PAO synthetic oils are a bit close to PFTE solubility parameter for comfort.......will look into it. Actually, I said 10, but it is more like 7-9, like you said.....WPL oils are very far away from that region. You bring up a great point about the effective Hildebrand solubility parameter of the combination of ingredients. On the other hand, you can just plop a seal into the oil and see if it swells....
  • + 2
 Awesome video. One question: Currently it's winter in the northern hemisphere and the temperatures can get very low, right now it's about -10°C in my country or even less. My fork (Manitou Mattoc Pro) is really sluggish in temperatures below 0°C. I can only use half of the travel and the rebound is slower. Is this normal with low temperatures? Obviously the problem is in the oil. On a long descent the oil warms up and it works great again. What do you recommend doing (specific type of oil?), so I can get quality performance from suspension in winter weather? Thanks.
  • + 3
 That is normal with low temperatures unfortunately. Try changing your oils out to lighter ones (the damper oil makes the biggest change, but in -10C it won't hurt to lighten the bath oils either), and open up your compression/rebound adjustments somewhat.
  • + 4
 I've had the pleasure of meeting Alex to discuss suspension oil in depth and I can say that he's truly an expert on his field and his products are amazing.
  • + 2
 Thank you. Main motivation is, for example:

Of the 1.4 billion gallons of lubricant oils used in the U.S. every year, 40% is lost due to evaporation or spillage into ground and waterways. That is way too much for me.....you even wonder where does the "properly" disposed oil go to?
  • + 3
 Hey Steve, can you touch on the relationship of certain oils and factory seals? Are seals designed/engineered around certain oils to create a better seal and therefore longevity?
  • + 3
 Not being a seal designer I can't say for sure, but in an ideal world they would be. Seals are imperfect at the best of times though - if you have more seal squeeze and therefore better sealing capacity, you increase friction and seal wear. In cases where you have relatively consistent or steady state movement and oil pressures (think car engines/transmissions) then you can begin to factor in seal lubrication to the design, but in cases with extremely erratic motion such as suspension, I can only imagine that would be extremely difficult to do.
  • + 1
 Positively, the big players in MTB suspension manufacturing design their systems and choice of oil//lower leg bath oil around seal swell compatibility. This is why - for example - in a RockShox BoXXer, Pike, Lyric etc. that you have a damper oil and a lower bath oil - which are entirely different oils. Same for Fox etc. Hat's off to these guys for trying to breakdown the insanely complex world of oils into layman's terms.
  • + 4
 Alex here....so, here comes the geeky answer. There is a parameter the scientists like Hildebrand and Hansen developed which characterizes the "chemical nature" of a polymer (elastomer). They were interested in predicting if a certain polymer was soluble in a particular solvent. The treatment is not difficult and it comes down to "like dissolves like". Like water does not dissolve oil but a mineral spirit does. So, if the chemical nature of the solvent is similar to the polymer....wham....it starts swelling and eventually dissolving, losing tensile strength, going to hell. What you could also do is washing out "plasticizers" which are added to the polymer to make them nice and soft and then your seals turns hard as a rock......not good.

So, here it comes....if the absolute difference in HIldebrand solubility parameter between the polymer (elastomer) and the solvent (suspension oil) is greater than 2, then they are compatible. This is based on experience and testing.

Now, which elastomer you say. Let's assume that all seals are made of NBR (Nitrile butadiene rubber under trade names such as Nipol, Krynac and Europrene), there is NO PROBLEM AT ALL since this elastomer has a solubility parameter of greater than 20, while WPL oils have a solubility parameter of about 15-17. So, we are all good. Having said this, let's pay tribute to mineral oils and PAOs which have Hildebrand Solubility paramters around ~10.

However, this analysis will depend on the type of polymer that you use....natural rubber (NR), styrene-butadiene rubber (SBR), epoxidized natural rubber (ENR), ethylene propylene diene monomer (M-class) (EPDM). You could just look up the value of the respective polymers and judge by yourself (all in interenet). But I think most manufacturers are using nitrile rubber, so, we can pretty much be cool about the whole thing. If we are talking about natural rubber....then we may have problems.

Does this help?
  • + 3
 Completely unrelated, but why don't they make shocks with even bigger negative chambers than they have now? Surely it would just heighten the benefits of the already added volume of the negative spring no?
  • + 8
 While I'm inclined to agree with you (the negative chambers we use are proportionally the biggest in the industry as far as I'm aware) there are limitations to that too. As negative chamber size increases, so does the pressure requirement, which means you then need a larger positive chamber to avoid excessive ramp up (which is why we recommend going down a size in volume spacer if you install one of our Corsets or dropping a couple of tokens if you install a Luftkappe). Eventually you run out of space, or have chambers so large that they weigh too much (as air can diameter goes up, so does the required wall thickness), and/or people are running the kind of pressures that create neutron stars etc.
  • + 2
 @VorsprungSuspension: on that topic, will you be offering Corset like air sleeves for CCDB air in the future? I know that there are some space restrictions on that shock but you are a smart guy and should find a way around it! Smile
  • + 2
 Thank you so much for the awesome video. Is it advisable to use regular 80w gear oil to relube the fork / shock after each wash? Or do we need to stick to certain manufacturer's fork oil eg the blue Fox Float Fluid?
  • + 3
 You do not need to stick to the OEM oils of the fork manufacturer, but you should try to use an oil with similar viscosity as the one recommended by the manufacturer.
  • + 4
 do does WPL do a flight club and get its biosynthetic fat from liposuction clincs?
  • + 1
 HAHA that would be amazing. They're vegetable oil based I believe.
  • + 1
 Good point and that would be a good source of oil for sure. However, not all oils are the same and the ones from human liposuction clinics contain a lot of saturated fatty acids, which would make your oil crystallize at pretty high temperatures, (think of butter or lard).....imagine that in your suspension. Maybe in Dubai (hot!) it would fly. Love fight club, but no go.
  • + 1
 Oleic acid then, they raid Italian restaurants lol

@VorsprungSuspension my luftkappe was despatched from tftuned today, looking forward to the change it makes.
  • + 1
 Terrific! For shock dampers, if vegetable oils keep their medium VI longer over use, could it be the petroleum/additive options just need a higher VI to start so that they still have adequate VI performance at midpoint in their useful life? Does high VI even matter in shocks that aren't dropping a thousand metres of vert at high speeds? Ease of working with veg oils plus the environmental factors makes me willing to put up with some heat fade...
  • + 1
 Thanks Steve! Great introduction to the topic! Can you speak to why someone like Push Industries (or Vorsprung) would use different oil specifications with their Fox 36 Factory re-valving service? Can you speak to how well these tuning services actually improve the forks performance and longevity for a given rider? Thanks again for all of the excellent and valuable content!
  • + 7
 I can't speak for other companies' rationale, but we use WPL oils in all fork services and certain shock services now, including revalving & custom work, simply because they're the best lubricants we've found in terms of reduction of friction. Fox's 20wt gold is also great as a lubricant, on par with ShockBoost 20wt for friction, but we find its adhesive qualities mean that it gets drawn past seals quicker than the WPL equivalent (Fox and several others actually had to redesign their wiper seals when they released the 20wt Gold for this reason). As a damping oil, it's great in forks, and suited to certain shocks but not so well suited to others.

As for how well tuning services work, that is not a realistic generalisation that can be made. Some make a world of difference, some are a complete joke; some are very arbitrary guesses and some are well measured. The end result to the rider depends on how well developed the tuning method is, how well the tuner has managed to interpret the needs of the rider - that one is an art form in itself - and how capable the tuner is of creating measured and quantifiable changes to meet the rider's needs. Read between the lines of anyone's marketing spiel, including ours, and you'll usually be able to get an idea of what you're really getting. This is definitely an industry in which skepticism is warranted.
  • + 1
 Hey Steve, a bit off topic but I've been trying to reach you via email and I'm not having any luck. Can you confirm an email address. I would like to talk with you about specific topics... btw the video series is excellent!!! Keep em coming!
  • + 1
 Hi Scott, I got your email, have just replied Smile
  • + 1
 I always thought that renewed feeling a air can service provides came from the seals alone but it sounds like the age of the additives might have an impact as well. How long do the additives last before degradation starts to impact performance?
  • + 2
 The additives are destroyed after 69 hours Smile

There are a lot of different additives in various oils, some of them break down relatively rapidly and some don't. In the case of air sleeve services specifically though it's less to do with oil breakdown and more to do with the fact that everything is clean and well lubricated again.
  • + 2
 This depends completely on the level of activity the shock is enduring as well as many other factors that affect the thermal stability of additives. We are running thermal stability tests in the lab and one thing is clear: oils with additives don't last nearly as long as oils without them.
  • + 3
 I could listen to you guys talk about this stuff for entire days at a time hahaha Smile

Keep up the awesome work.
  • + 4
 Thanks again, Tuesday Tune is getting me through winter
  • + 2
 in the early 70s we put Type F Ford Automatic Transmission Fluid in our motocross bike forks and it worked well... how would something like that work now?
  • + 1
 Not all that badly actually, but it's not as good as the right tool for the job. Quite a few people have tried ATF as a splash bath oil over the years, us included, and while it's functional enough it's definitely not as nice a lubricant as something like WPL's ShockBoost 20wt, for example.
  • + 1
 I noticed that you did not mention fluorinated oils. I would be extremely interested in understanding how perfluorinated oils would perform with mtb.
  • + 2
 Another great installment. Most people don't realize the intense amount of engineering that goes into oil design.
  • + 1
 Biolubricants are a fairly new area of innovation that we are happy to be a part of!
  • + 1
 Very good video guys Alex, very good explanations of fuzzy rope ! I liked it !
  • + 1
 String of pearls (mineral oil), fuzzy rope (PAO), stars (triglycerides), still working on monoesters......just remembered that stars have 5 points, not three. Need a 3-point structure found in nature to describe our oils.
  • + 2
 Great work again Steve (and Alex), I was hoping you'd do one on oils
  • + 2
 WPL stuff is Awesome! Keep up the good work!!
  • + 1
 had to tell me not to cook with my suspension fluid, what a buzzkill.
  • + 4
 Isaac from WPL actually cooked eggs in ForkBoost once, just to prove a point. Apparently not the greatest tasting things ever though...
  • + 2
 My favourite program.
  • + 1
 Awesome info guys, thanks! More of this please.
  • + 2
 interesting
  • + 1
 Whats in my oil.... shit.. is there even oil in there!
  • + 1
 70% oil and 30% additives.....

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