Fork Oil Recommendations

[northwestparider]

I'm curious what everyone is using for fork oil. I need to do the seals so I figured I would clean and refill them. @CYYJ mentioned 10w oil.

I stopped at the local Honda dealer and they didn't have any which I was told was Honda SS-8. They did have some 10w oil in Maxima Racing Oils, for $17.49 a quart. I know I'm a tight wade, but geeze this sounds expensive.

What are you guys using? With my 83 V65 Magna I used Honda Fork Oil years ago, but there is a nagging feeling in the back of my mind that someone then said I could use tranny fluid. Is this absurd?

Anyway, I'm interested to know your thoughts.

 

[motornut]

Go stock weight and use a good brand, Maxima is just fine but there are a lot of good oils out there on the market

 

[jonz]

I'm in the same boat as my ST1300 fork seal is leaking. I remember a long time ago (30 or so years) using ATF in dirt bike forks and it worked fine. Suspension is a little more sophisticated now not to mention ATF chemistry. I'm inclined to go with the recommended weight as I'm pretty happy with the ST1300 fork compliance. I know on my ST1100, it felt a little soft so I went from 10 wt to 15 wt and was happy with the firmer ride. Honda doesn't refine for oil so I'm inclined to use any 10 wt if that is the consensus weight to use.

 

[gmtech94]

that is reasonable compared to what we pay up here . A liter is about $40 and that is for cheaper fork oil . I have some Silkolene at about $ 100 a liter and you need about 3 to do your forks . Motocross guys usually have some of the slipperiest oil and a lot of them are sponsored so it is a bit cheaper .

 

[Andrew Shadow]

I was told was Honda SS-8. They did have some 10w oil in Maxima Racing Oils

According to a previous post by Dave, Honda SS-8 is 10 weight oil, so the Maxima should be good if that is what you want.

I mixed stock Honda Showa SS-8 fork oil that is nominally 10wt with Honda's SS-7 nominal 5 wt oil

I believe that it was Dave (@dduelin) who also had posted a chart that listed what the weight of many fork oils actually is.
i.e. Honda SS-8 is not an 8 weight fork oil, it is actually a 10 weight fork oil, Honda SS-7 is actually a 5 weight fork oil, etc..
The chart allowed comparisons to be able to find equivalencies between the different brands of fork oils. If I remember the post correctly it was because there doesn't seem to be any standardized viscosity rating system for fork oil like the viscosity standards used by engine oil manufacturers.

I don't seem to be able to put my finger on it right now, so maybe Dave will chime in to clarify.

 

[dduelin]

Suspension Fluid - Pvdwiki

www.peterverdone.com

Too much information for some (SAE weight is not an accurate description of fork fluids) but the chart is useful for objectively choosing oils in relation to Honda SS-8 from the factory or Honda dealer stock. Wanting something thinner find the Showa SS-8 and go up the chart and find an oil with numbers lower than SS-8 or below for an oil that has thicker flow characteristics. I recall ATF is listed in the chart.

 

[Al st1100]

Used synthetic ATF on my ST1100, happy with results.

 

[Igofar]

Many, if not all of the Honda service manuals for many years called for type F ATF fluid, which is 10 weight oil.
Showa 10 weight oil is ATF fluid.
I sent a sample of Honda SS8 to the lab for an analysis (virgin oil) and they verified that the very expensive Honda branded pints were in fact ATF fluid.
That said, there are some differences in some of the new designs in suspensions that require special lighter fluids, but the the old style ST forks, ATF works perfectly.

 

[dduelin]

That’s one lab analysis I would like to read in its entirety.

 

[Igofar]

We went through your defending brand loyalty last year sometime, and someone also posted many Honda service manuals recommending ATF, you didn’t want to believe that either, and somewhere on that post I believe I posted the UOA of the Honda fork oil/ATF info.
You even tried to defend Showa special fork oil, which Showa even stated was 10 wt. ATF fluid.
Don’t believe everything you think, or want to believe, as you may be wrong.

 

[dduelin]

Many, if not all of the Honda service manuals for many years called for type F ATF fluid, which is 10 weight oil.
Showa 10 weight oil is ATF fluid.
I sent a sample of Honda SS8 to the lab for an analysis (virgin oil) and they verified that the very expensive Honda branded pints were in fact ATF fluid.
That said, there are some differences in some of the new designs in suspensions that require special lighter fluids, but the the old style ST forks, ATF works perfectly.

The only ATF fluid, Red Line High Temp, on this chart flows half again thicker than SS-8. True that ATF can work well in older style damper rod forks that predate the ST but the ST1300 has modern cartridge forks that usually spec a much lighter fluid. Can you share the referenced lab analysis with us?

 

[ASPC]

We went through your defending brand loyalty last year sometime, and someone also posted many Honda service manuals recommending ATF, you didn’t want to believe that either, and somewhere on that post I believe I posted the UOA of the Honda fork oil/ATF info.
You even tried to defend Showa special fork oil, which Showa even stated was 10 wt. ATF fluid.
Don’t believe everything you think, or want to believe, as you may be wrong.

He doesn’t always agree with user manual. Here he says Honda is wrong.

 

[acedantinne]

Bel ray 10# use this fork oil for years. Sold at the Honda shop I worked at.

 

[dduelin]

For my part this technical discussion has nothing to do with brand loyalty or whether or not older Honda manuals allowed use of ATF in the forks. The ST1300 doesn't have damping rod forks rather it has cartridge forks that allow a set of shims to progressively open and allow the compression damping rate to taper off with speed of compression. Damping rod forks can't do this with their simple fixed orifices. Let's start from there. There can be no logical disagreement as to the differences between cartridge forks and damping rod forks. Fluids like ATF that work well in damping rod set ups are probably not going to be optimal in cartridge forks but opinions can and do vary. I base the following thoughts on technical merit and am happy to discuss same. Turns out that Type F ATF has numbers that suggest somewhat thicker flow rates compared to the stock Honda fork oil so I personally would not go in that direction but others are free to do so.

This site does clearly explain why the use of SAE weight does not work well when comparing very light oils commonly used in forks. We also know the flow characteristics of a fork fluid labeled "10 weight fork oil" of any brand can vary considerably from another brand of 10 weight fork oil just by looking at the chart on this updated chart here Since UOA labs are normally working with engine lubricating oils it would be helpful to know how they determined the viscosity of a virgin sample of ATF and how they compare it to values of a known fork oil like Honda SS-8. If the lab stated viscosity in SAE weight the results are essentially meaningless unless they also give flow rates in centistokes at different temperatures and the stability of the flow rates at the standard temperatures (VI or viscosity index). I'm pretty sure I would have noticed that problem if the UOA numbers were in that other thread mentioned SAE or were given in SAE. If the flow rate is given in the viscosity grades and VI used in the list of oils it's simple to say "Yes, the sample compares very close to Brand X." I've never seen an UOA that uses ASTM standards. Not saying they don't but since they deal exclusively with testing engine oils defined with SAE standards it is very unlikely. Hence the request to show the analysis. Not worth beating that horse.

So for anyone reading this far and is seeking to alter the fork's characteristics by changing the oil "weight" it is helpful to think about what you want to do with the fork action. It's commonly held the ST1300 is undersprung and overdamped for the non Japanese ideal rider. It has way too much sag under the lightest of riders. To help with the soft springs Honda specs a high fork oil level, 62 mm, to help keep the fork from bottoming out. Oil height can make a soft spring feel "stiffer" at the last 1/3 or 1/4 of travel as air is compressible but oil is not. Many riders complain of a harsh feel on large or sharp bumps. I liked the ride of my '05 on small bumps and wanted to keep that. If we want to try and lessen the overdamped or harsh feel on sharp bumps we could try an oil with lower centistoke numbers and a relatively high viscosity index. Benchmark against whatever oil you are using in the fork now and choose the next oil you want to try. Just changing to a lower "weight" oil on the bottle may not necessarily give the results desired but by choosing the oil based on known characteristics we can easily fine tune the fork to our liking. Alternatively to changing oils one could replace with the same oil or one close to it and lower the oil level 15 or 20 mm and see if the harshness on sharp bumps is reduced. If it matters the following is what I did to my bike. I weigh about 165 lbs in riding gear and the fork had 47 mm of rider sag or 44%. Way too much, I wanted a target sag of 30 - 35%. I made spacers 16 mm longer to get sag to 36 mm. I replaced oil with Bel Ray 10 wt oil without knowing anything about why except it was available and it was "10 wt. on the bottle." Turns out it's numbers aren't too far off from the OEM Showa SS-8 but I still felt the suspension was too harsh and the bike ran wide on corners with small bumps. I next tried a 2 to 1 mix of Honda SS-8 and lighter SS-7 to reduce damping harshness but not too much just trying to get rid of the jittery feel over small bumps when cornering. This worked well for me. If it did not I would have tried 100% SS-7 next or an oil close to SS-7's values. By then I had found the Peter Verdone website, done a track day, and began to learn more technically about what I was trying to do. Suspension tuning is part science and part art. I found what works for me and your results could be quite different.

 

[Igofar]

Ooooh you read a book and had a track day
It must have taken you a lot of time to look up all those comments you want folks to believe they were yours.
You want real answers, buy a bottle of Honda ss8 and send it to the lab. It will only cost about $20 bucks, and they will be glad to provide you whatever info you want.
I would recommend you cut and paste all the comments you posted here also, as I’m sure the guys in the lab could use a good laugh.

 

[Igofar]

But to be fair, maybe your home brew of mixing bottles of fluids, and using plastic kitchen sink trap pipes, as pre load spacers works better than all the professional suspension shops who rebuild hundreds of these for a living.

 

[Daboo]

...I believe that it was Dave (@dduelin) who also had posted a chart that listed what the weight of many fork oils actually is...

This is just one of many charts you can find with a simple Interweb search. The point is that fork oil weight numbers are not accurate like engine oil numbers are. Go down about six lines from the top and you'll see Torco RFF 10. The value is 19.90. Go to the next line down and you'll see RockShox 5W which looks like it is made by Torco. It has the same value of 19.90.



I used Maxima 10 wt oil on my BMW for one change. It was cheap and recommended by the manager. The next time I changed fork oil, they didn't have it, and all they had was the Bel-Ray fork oil at twice the price. Ugh. I didn't have a choice. But the suspension felt better than before. Bel-Ray isn't shown on the chart, but it doesn't matter to me. I have the front end response that I like very much. I don't care about the price. I'll buy the Bel-Ray. Not because it is "better". Not because it is more expensive. But simply because it gave me the response I was looking for.

I'm in the same boat as my ST1300 fork seal is leaking.

Have you tried the Sealmate "tool"? Or equivalent? I've used it and removed some grit that was causing some seepage. Months and many thousands of miles later, the fork seal is still good. I carry a couple that I cut out of some thin plastic in my tank bag.

Chris

 

[jonz]

Have you tried the Sealmate "tool"? Or equivalent? I've used it and removed some grit that was causing some seepage. Months and many thousands of miles later, the fork seal is still good. I carry a couple that I cut out of some thin plastic in my tank bag.

Chris

I've got the Seal Doctor tool on one of my motos somewhere. Thanks for the reminder - I'll check my motos up here. Murphy's Law says it's probably on my 1290 in southern California.

 

[dduelin]

This is just one of many charts you can find with a simple Interweb search. The point is that fork oil weight numbers are not accurate like engine oil numbers are. Go down about six lines from the top and you'll see Torco RFF 10. The value is 19.90. Go to the next line down and you'll see RockShox 5W which looks like it is made by Torco. It has the same value of 19.90.



I used Maxima 10 wt oil on my BMW for one change. It was cheap and recommended by the manager. The next time I changed fork oil, they didn't have it, and all they had was the Bel-Ray fork oil at twice the price. Ugh. I didn't have a choice. But the suspension felt better than before. Bel-Ray isn't shown on the chart, but it doesn't matter to me. I have the front end response that I like very much. I don't care about the price. I'll buy the Bel-Ray. Not because it is "better". Not because it is more expensive. But simply because it gave me the response I was looking for.


Have you tried the Sealmate "tool"? Or equivalent? I've used it and removed some grit that was causing some seepage. Months and many thousands of miles later, the fork seal is still good. I carry a couple that I cut out of some thin plastic in my tank bag.

Chris

Plus one on the Seal Mate tool or equivalent. I have used a Seal Mate to stop a weeping fork seal on several bikes and recently on the outer final drive seal on my RT. 7 or 8,000 miles later the weep has not returned.

 

[Mark B]

So what fork oil do we use??????