The Confusion that is Fork Oil

[RossKean]

The "weight" of the oil IS the viscosity - measured in some way or other. There is a large temperature coefficient for many oils although this is somewhat less for "Multigrade" oils (i.e. 10W30 motor oil)

You might have to look into it but it is possible that the range of centistoke values reflects the conditions under which the tests were performed. Given the very large change in centistoke values for a temperature range, I still maintain that anything reasonably close to the target would be just fine.

 

[Fred W]

No, I disagree completely. The viscosity is measured in centistokes at a particular temperature. The weight rating is arbitrarily assigned by the manufacturer and is not strictly defined for suspension fluids. That is why you cannot just go by the weight rating printed on the bottle.

I also know for a fact that a suspension fluid that has a viscosity of 30 cSt (over twice the manufacturer's recommended viscosity) will not work right in a fork designed to use suspension fluid of 15 cSt, no matter what is printed on the bottle. Even if you were able to adjust the low speed circuit open enough, the non-adjustable high speed orifices would be far too small and the fork would work like crap.

 

[RossKean]

There is a direct relationship between SAE viscosity (i.e. SAE 20) and the viscosity measured in centistokes. Perhaps the differences we are seeing are a function of the temperatures the measurements are made. For SAE single weight oils, I believe that the standard is measurement at 100 °C. This is obviously different from the operational temperatures of a motorcycle fork. Different oils may have very different temperature coefficients although the measurement at 100 °C could be the same. The problem is not the measurements themselves but the lack of definition on the conditions for the tests.

Here (link below) is a direct comparison table for SAE viscosity and Centistokes. I understand that although two oils may have exactly the same viscosity measurement at the standard test conditions, they may behave very differently under the conditions where they are actually used. So, I guess I am agreeing that you can't go simply by the SAE rating (viscosity) on the bottle because that number was not determined at the operating temperature for the oil. Even the 40 °C determination may not accurately reflect the oil's behavior at 20 °, although I would expect it to be closer to reality.

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=634236

 

[Fred W]

SAE weight ratings are for engine oils and specify their viscosity at 100 degrees C, which has little to no meaning when comparing fork oils. Excerpt from Peter Verdone's wiki page

Viscosity (ISO)Modern fluid viscosity ratings are on an ISO VG (visocosity grade) using test standards set down by ASTM D-2422-97 (2002)& ISO 3448:1992 system of: cSt@40C / cSt@100C / VI. ‘cSt’ stands for CentiStokes, an accurate dynamic measure of viscosity (ISO 3104:1994 & ASTM D445-04). Using these numbers, you can tune oil viscosity with a very high degree of precision in a specific heat range. A straight line graph made from these two viscosity numbers at each temperature can give a very close approximation of the oils viscosity at any other usable temperature.

ISO Grades Courtesy of Shell Oil.

SAE Oil WeightDO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.

These problems can be seem graphically by comparing several systems to each other. Viscosity comparison chart Courtesy of Shell Oil.

Suspension oil is labeled by weight because consumers are used to thinking of oil (ie. motor oil & gear oil) in these terms. The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require

 

[Fred W]

SAE weight ratings are for engine oils and specify their viscosity at 100 degrees C, which has little to no meaning when comparing fork oils. Excerpt from Peter Verdone's wiki page

Viscosity (ISO)Modern fluid viscosity ratings are on an ISO VG (visocosity grade) using test standards set down by ASTM D-2422-97 (2002)& ISO 3448:1992 system of: cSt@40C / cSt@100C / VI. ‘cSt’ stands for CentiStokes, an accurate dynamic measure of viscosity (ISO 3104:1994 & ASTM D445-04). Using these numbers, you can tune oil viscosity with a very high degree of precision in a specific heat range. A straight line graph made from these two viscosity numbers at each temperature can give a very close approximation of the oils viscosity at any other usable temperature.

ISO Grades Courtesy of Shell Oil.

SAE Oil WeightDO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.

These problems can be seem graphically by comparing several systems to each other. Viscosity comparison chart Courtesy of Shell Oil.

Suspension oil is labeled by weight because consumers are used to thinking of oil (ie. motor oil & gear oil) in these terms. The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require

 

[MajBach]

Well all I wanted to know was what oil to put into the forks to give me a slightly stiffer ride than I had previously. Now that I am aware that you can't tell anything about an oil by the label and that the viscosity I require can change depending on the valves in the forks, I haven't a clue what to use.

Good thing engine oil choices are cut and dry.

 

[Fred W]

Look at the big suspension oil viscosity chart here and pick one that has nearly the same cSt rating at 40 F as the Yamaha 01 fluid, say anywhere between 15 and 18 cSt. Buy that and use it. It doesn't get any simpler than that.

To make your forks feel stiffer increase the compression damping adjuster. Putting thicker oil in there is a bad idea as it also increases the unadjustable high speed damping, both in compression and in rebound, which is not what you want.

 

[MajBach]

Look at the big suspension oil viscosity chart here and pick one that has nearly the same cSt rating at 40 F as the Yamaha 01 fluid, say anywhere between 15 and 18 cSt. Buy that and use it. It doesn't get any simpler than that.
To make your forks feel stiffer increase the compression damping adjuster. Putting thicker oil in there is a bad idea as it also increases the unadjustable high speed damping, both in compression and in rebound, which is not what you want.

Well that does help me to better understand the do's and don't and especially the why's. But as mentioned earlier, I had a fork upgrade and GP Suspension uses a different cSt rating oil for their adjustments. Perhaps I will give them a call.

Thanks

 

[Fred W]

Then let me just ask: Why the **** didn't you just do that to begin with?

 

[MajBach]

Then let me just ask: Why the **** didn't you just do that to begin with?

Nice.

Because I didn't realize it wasn't so cut n dry until I read this thread. And clearly I am not alone.

 

[Fred W]

...

 

[Nanahanman]

An interesting and informative thread. (another oil thread LOL)

It seems, at least for fork oil, the easiest solution is to buy the manufacturers recommended product for a stock suspension.

May cost a bit more but it's not like one has to buy it all the time.

Thanks to all for the great info

 

[BanjoBoy]

Look at the big suspension oil viscosity chart here and pick one that has nearly the same cSt rating at 40 F as the Yamaha 01 fluid, say anywhere between 15 and 18 cSt. Buy that and use it. It doesn't get any simpler than that.
To make your forks feel stiffer increase the compression damping adjuster. Putting thicker oil in there is a bad idea as it also increases the unadjustable high speed damping, both in compression and in rebound, which is not what you want.

Great stuff Fred.

Back in the late '80s, early '90s whilst my buddies were racing AFM 'n AMA, we worked closely with a great suspension guru named Jim Lindemann. :RIP:

He always used Roc/Rock? oil from England, but after checking my earlier link, the company has changed. I'm gonna change my fork oil soon, (And add me sum All Ballz) and this here info you provided is great! So don't be so hard on Bach, yer help'in other here.

 

[MajBach]

...You seriously don't see what you just did? You asked us for help selecting a fork oil, and after a bunch of input, all of it helpful, you tell us: I'll just ask the guys I bought my suspension parts from.

So seriously, why would you have not done that in the first place if you weren't going to pay any attention the the advice you were given?

Why should anyone make the effort to help you again?

Well let me paint the picture for you, Fred

It started when I combed through several threads on several forums to learn about fork oil. When I came across this one, there was clearly justification to not grab just any oil off the shelf.

I received a recommendation from one mechanic to go to a heavier weight oil because I am a heavier guy, suggesting to me that the weight of the oil has a relationship with the desired level of damping; something you contradicted earlier in this thread.

Then I received a recommendation from someone who was just as much a stranger to me as you or anyone else on this thread to use a specific oil. That oil, however, was not listed on the viscosity charts and it appeared to have several variations as I illustrated earlier.

YOU also stated that early in the thread that you can't go by what you read on the bottle nor by what was done yesteryear, you have to go to the charts. But the charts that have been referred to so far are either outdated, missing a published date, not from a credited sources, and/or missing currently produced oils.

Then it was stated:

The Motul 5W factory line is the fully synthetic and is the closest to the Ohlins R&T43. Without the exact figures from Yamaha I have been working on the assumption that the M1 is the same or damn close to the Ohlins (19 cSt). My choice would be the Motul 5W (18 cSt) or possibly Silkolene 02 which is also fully synthetic (17.94 cSt)

Then you wrote:

I had never noticed the changes before this thread, but going back through all of the specs that I've accumulated I now see that the Yamaha 01 suspension fluid was only the specified fork oil for 1st Gens. For all second Gens from 2006 thru 2012 only Ohlins R&T43 in the specifications charts. And now all 3rd Gens (both A and ES) the charts specify Yamaha M1 suspension fluid.

and further:

Going with replacement aftermarket valves (or cartridge) can lessen the need for such a thin suspension fluid by increasing the number and size of the high speed orifices. If you have upgraded your fork valves you really NEED to ask the manufacturer what viscosity (in cSt) they recommend with their valves. Just make sure that they understand that the bike will be used on real world streets, not a nice smooth race track.

That's when I piped in stating it was all as clear as mud. Immediately, someone raised the point :

GP Suspension used Motorex 5w fork oil to develop their damping cartridges and that oil has a viscosity of 22.6 Cst at 40C which is pretty close to a number or other premium fork oils, some called 5w and others called 7 or 7.5 wt. I have also mixed oils (Honda SS7 and Honda SS8) to achieve that viscosity with good results. When Jay brought Motul 7.5 to tech day to install in his forks we searched the Internet to verify the actual viscosity of that oil but were unsuccessful, but he has been very happy with the results so that is an viable alternative if you can find it. Maxium 7w is the right viscosity, easy to find, and seem to be a favorite of many suspension shops.

But this doesn't clear anything up for me but rather raises more questions such as: does this apply to 25 mm valves or just the cartridges? And, is "22.6Cst too high" since it falls outside the window that you recommend. Plus, in another thread, someone stated the brand they use is different than the one quoted above. I also found that there was more than one "Motul 7.5" and more than one "Maxium 7w" (actually, it was called Maxima - -or is this another brand? Oh wait...what's Motrex?).

Plus, I don't know if "Jay" has the same front end as I do so his results mean nothing. Don't forget that YOU stated that you have to match the viscosity to the valves, not to the rider or the OEM recommendations. But wait...didn't also state that the oils the aftermarket guys use/recommend is geared to the "smooth track" and shouldn't necessarily be used for normal riding conditions ?

Then you've got one person stating how stark the perceptable difference is when you use the wrong weight oil, another person stating we're all splitting hairs and you say to make sure the cSt falls within such and such a window ( if you're using OEM suspension, which I am not ).

Of everyone contributing to the thread, your tone implied to me more than anyone else that you were the resident expert, but then your stock fell when you implied that you didn't even know what the SIS-VI numbers that are plastered in bold on all bottles of fork oil meant, and you reinforced my belief that this is not a simple as I thought it would be. : Good to know. Unfortunately it is not widely adopted, so only helps if comparing those that do use that technique. It's not like they are making it easy for us. Right?

I looked on my invoice from GP and it stated that they used a "5wt" oil but nothing more specific.

But you then wrote :

See, here's the problem. You know you want something similar to the OEM stuff. People say you should use a 5 weight fork oil. You look on the shelf at your LBS and you see an assortment of 5 weight fork oils:. What you do not see is the centistoke ratings of the oils in parenthesis below

Torco RFF 5 (10.75 cSt)

Maxima Fork Oil 5 Weight (15.9 cSt)

Maxima Racing Fork Fluid 5 Weight (15.9 cSt)

Silkolene Pro RSF 5 Weight (26.7 cSt)

Castrol Synthetic 5 Weight (28 cSt)

PJ1 Fork Tuner 5 Weight (31.2 cSt)

Shell Advance 5 Weight (33.05 cSt)

Combine that with the statement you made earlier of the necessity to inquire direct to the mfg on what oil they use to develop their valves and the recommendation that you made NOT to regard the weight of the oil as something you use to adjust your suspension, I was still far from making an informed decision. The fact that you "disagreed completely" with another in depth contributor to this thread also thinned the reliability of what I was reading from others. Keep in mind as well that all this occurred in what, a 24 to 48 hr period?

And the reason why I didn't call GP in the first place? Well, because it's a business and businesses often do some things on the cheap. Plus I would have to go through a receptionist to get that information. So I figured better to try someplace like this forum first.

So in summary, the reason why I am contacting GP is in fact because I am paying attention to all the advice I was being given. I think you just got upset when I didn't follow yours exclusively.

 

[MCRIDER007]

MajBack, I have been following your childish, repetitive, never ending questions about Suspension 101 for almost 5 years and you don't appear to be capable of learning anything but enough data to ask another question. You seem to be the type of person that will ask someone to write down a phone number, then ask that person to write down detailed instructions how to use a phone, then ask that person to show you how to use a phone, and finally ask them to make the call for you. A perfect example is when you picked up your bike at GPSuspension, completely ignored their attempts to explain how to adjust the suspension, and then came on this Forum to ask 50 questions on suspension adjustment

I told you exactly what fork oil viscosity you needed for your bike with its GP Suspension components and why...but you still found a way to question and distort my comments. Buy some fork oil, 5w, 7w.....whatever, go to Tech day, pay attention for once and learn how to change it, and if you don't like the result then change it again to something different when you get home and quit wasting everyone's time.

 

[Fred W]

MajBach. You are mixing up my replies to other people with replies to you, and taking my posts completely out of context. That is either sloppy or dishonest. This isn't the first time we've had these communication problems, you and I.

Not having ever owned a 2nd Gen, and not having yet changed the fork oil in my 3rd Gen forks, I was unaware Yamahas spec had changed before this thread. Mea culpa. I am not an expert, nor have I ever represented myself as a "suspension expert". Just a guy that can figure things out logically. Not having committed the specs to memory doesn't change how one selects a suspension fluid, or why.

My replies were generic in nature and part of the general discussion in response to evaluating which suspension fluids to buy and why. I did not make any recommendation to you to use any particular oil, or even one of any particular viscosity. What I posted was that if one were trying to reproduce the Yamaha 01 fluid then they would find oils within a small range of viscosities.

Since you knew all along that you had aftermarket suspension valving (which I did not know) then your best bet would have been to ask the suspension maker GP what they would advise using for their valves. I even said as much verbatim. Once you know what oil they recommend you can look up what the viscosity of that is, and then find suitable substitutes that have the same or similar viscosity.

 

[MajBach]

Not trying to stir up ****, just find this all confusing and ambiguous, especially when intermixed with a busy day. It just became personal and condescending and I didn't care for that. The frustration you felt could have been communicated using a different choice of words or via PM I think, which would have resulted in me being a little more receptive to the "communication problem" you refer to. I can assure you I am not being dishonest or rearranging statements to somehow support my case. I've learned as much from this as I can reasonably expect to and I will go from there.
Thanks for your input.

Incidentally, I have no idea what your are referring to. Any hard feelings you and I may have had in the past are loooong since forgotten.

MajBach. You are mixing up my replies to other people with replies to you, and taking my posts completely out of context. That is either sloppy or dishonest. This isn't the first time we've had these communication problems, you and I.

 

[bigjohnsd]

Aside from the past several posts, I think this thread still warrants a sticky

 

[BanjoBoy]

SAE weight ratings are for engine oils and specify their viscosity at 100 degrees C, which has little to no meaning when comparing fork oils. Excerpt from Peter Verdone's wiki page

Viscosity (ISO)Modern fluid viscosity ratings are on an ISO VG (visocosity grade) using test standards set down by ASTM D-2422-97 (2002)& ISO 3448:1992 system of: cSt@40C / cSt@100C / VI. ‘cSt’ stands for CentiStokes, an accurate dynamic measure of viscosity (ISO 3104:1994 & ASTM D445-04). Using these numbers, you can tune oil viscosity with a very high degree of precision in a specific heat range. A straight line graph made from these two viscosity numbers at each temperature can give a very close approximation of the oils viscosity at any other usable temperature.

ISO Grades Courtesy of Shell Oil.

SAE Oil WeightDO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.

These problems can be seem graphically by comparing several systems to each other. Viscosity comparison chart Courtesy of Shell Oil.

Suspension oil is labeled by weight because consumers are used to thinking of oil (ie. motor oil & gear oil) in these terms. The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require

Thanks Fred.

After much study 'n read'in of Peter's Wiki page, think I'm gonna go with the Red Line light. (Yellow) My rebound is maxed out, (Cuz I have stiffer springs) so something slightly "heavier" than Yamaha 01 (Or the Maxima racing I have in there now.) should do the trick. I may lose sum high speed compliance, but with summer come'in on (With a vengeance!) here in NORCAL it should be fine.

Just one more thing to consider with the confusion that fork oil is; the temperature where yer ride'in, 'n the kinda roads ya ride on. :crazy:

 

[HotRodZilla]

If people are "Trying to replicate the Yamaha 01 fluid" why don't they just buy THAT fluid? Is it a matter of a couple of cents, or this another, anal FJR, "I have to find something that is the same, but is better" game so many here love to play?

I cannot believe the OP didn't call GP suspension immediately when he had a question. If he is the same weight as when he had the forks built, I would bet they would recommend the same fluid. If he's heavier, they'll know how to adjust for that, within reason.

THIS is why I pay my Yamaha dealer to do my forks. They have been perfect every time!