Can anyone tell me what the kinematic viscosity of this fork oil is (in cST@40)?

Is it the same stuff as Yamaha Suspension G10?

Peter Verdone Designs - Low Speed Damping

Thanks

I spent 45euros in 3 litres of PUTOLINE 15W fork oil to fit on my XT's front end (has YZ250 forks) behaves wonderfully!


Don't know about the weight of that other oil tho...
Good luck!


Vando

ATF fluid works fine, i use it & its cheap.

Sorry Ralph thats not the answer you wanted eh.

Mezo.

And to follow up on Mezo's input, have a look here;

Ever wonder about fork oil? - ADVrider

a long report and intresting if not disturbing!

Socks

Just buy any old fork oil.. As long as it's the correct viscosity, you don't need to be spending £££££

The suspension on the XT is pretty terd anyway so getting anal on oil quality will make zero difference.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

That's my issue. I'm not bothered about oil quality or trying to make it better, I just want to keep the damping as it is, nice and compliant for off road use, but not wallowing on road. The Yamaha G10 oil is 33 cST@40, so I need to find something with a similar viscosity. Since, as posted above, the SAE system is pretty useless for measuring viscosity of a hydraulic fluid, I don't just want to go out and buy any old 10w oil and shove it in, I've made that mistake before on damper rod forks as it turned out the 10w I bought was more like a 15 or 20w in most other manufacturers oils.

The Silkolene 10w fork oil fits the bill, but you need just over 1/2 litre per fork, and I can only find it in litre bottles, so I need to buy about twice as much oil as I'm going to use.

The Yamalube 10w comes in 500ml bottles, but I can't find the cST@40 rating anywhere.

hmm !

If you buy a reputable brand of oil, it's going to be the weight on the bottle..

If you want to improve your XT suspension, change it or learn to live with it.

The components are cheap and built to budget. The oil is a very small part in the equation.

You could try some progressive Hagon springs but they will only help so much.. Springs can only be progressive so much before they seriously stop doing what they're meant to do.

You really can't have the best of both worlds. You simply can't have plush off-road suspension which doesn't wallow and dive while hard braking on tarmac.

Have it stiff and suffer off-road or keep it supple and learn to deal with the diving.
There will always be a compromise. You have to decide how you do most of your riding and what you're willing to live with.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Have read of that link Ted (but ignore the Castrol Fork Oil 10wt at 15 cST@40, I find it difficult to believe Castrol would label an oil that light as a 10wt, that may be a misprint, but then again maybe not).

A Silkolene Pro RSF 10w oil is 40% heavier than a 10w oil from the Silkolene 'Maintain' range. The Pro RSF is a high spec oil from the 'Race' range designed for cartridge forks on a sports bike, so you'd normally use a 5 or a 7.5wt, so the 10w oil in that range is really heavy, and that tends to be true of all the synthetics. The 'Maintain' range is more suited to damper rod forks.

This kind of viscosity difference is also true between different reputable brands of 10wt fork oil.

Put anything over 40-45 cST@40 in a damper rod fork and you may start to get a hydraulic lock on your fork when it hits sudden changes in road surface, such as dropped curbs or dropped/raised manhole covers. The heavier oil just can't get through the holes in the damping rod quick enough, so your fork stops. And it would be very uncomfortable off-road.

Not trying to improve, quite happy with my damping as it is now. Just make sure I don't choose the wrong oil and over or under damp my bike, which would be very easy to to inadvertently if you just go and pick up an oil of the shelf based upon the wt rating, particularly if you've had some bad advice that's told you to use a heavier oil weight, such as a 15wt, to control damping on the road.

Think I'll just have to buy 2 litres of Silkolene Maintain, or look at the ATF fluids as suggested by Mezo, I can't find any oil of about 33 cST@40 that I can buy in the UK, which comes in a 500ml bottle.

Well, I have to admit i'm surprised. These things are quite well regulated and have a list of standards to comply with... SAE for one.

But from that website, the whole system seems a pile of crap. You would of thought that motorcycle manuals, literature etc haven't mentioned this in the last 50 years or so Just think of the law suits ??? ... Obviously, some manufacturers do recommend their own brand oil or an affiliate. Maybe that's why !!

I've never seen a Clymer or Haynes say "use this brand and not this brand" though. You would think they would if there is such a huge difference that can cause hydraulic locks. Again, just for legal law suits etc !

I'm still not totally convinced. I've seen countless websites full of charts, figures and graphs in the past. Just because it looks official and well designed doesn't mean it's right...

More research required on this one but very interesting.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

I don't think there is many 10w on that list that would cause hydraulic lock, maybe the Motorex at 52 cST, so haynes are pretty safe just to give the wt rating.

SAE is a good measure for a lubricant, but cST is the right way to measure a hydraulic fluid. It's the way all the manufacturers measure their oils, just that for some bizarre reason they'll put it on the specification datasheet, but not on the bottle. It's thought that people understand better what the wt rating means, because of the SAE system used on lubricant engine oil, so that's what they put on the label. Look at these spec sheets from the manufacturers. Some even tell you what mix ratios to use if you want to achieve a certain kinematic viscosity. On the Silkolene one, you'll even note that the SAE rating and the wt rating are completely different! The wt rating is really nothing more than a 'name' given to distinguish between the different viscosities of oil available within the same range from that manufacturer. They might as well not bother with a wt rating and just call it 'Light', 'Medium', 'Heavy' and 'Very Heavy'.

http://www.motul.com.au/product_line...LEND_CHART.pdf

http://www.silkoleneoil.com/pdf/ProRSF.pdf

http://www.spectro-oils.com/pdfs/tec...Oils_Chart.pdf

http://www.maximausa.com/shopping/in...products_id=45

I started researching this and found the Motul spec sheets after a I caused an SV650 fork to hydraulic lock on a regular basis by putting a Motul Expert 15w in, but I knew loads of people using 15w oils and stiffer springs to improve the SV650, and they didn't have the problem. If you look at the Motul spec sheet though I was using an oil with a cST of 57! The OEM 10w Suzuki oil has a cST of 33. The oil was totally unsuitable.

Anyway, we've got completely off topic, and if anyone does know what the cST rating of a Yamalube 10w is, I'd love to know!

Here,s some more info

The Society of Automotive Engineers (SAE) has established a numerical code system for grading motor oils according to their viscosity characteristics. SAE viscosity gradings include the following, from low to high viscosity: 0, 5, 10, 15, 20, 25, 30, 40, 50 or 60. The numbers 0, 5, 10, 15 and 25 are suffixed with the letter W, designating their "winter" (not "weight") or cold-start viscosity, at lower temperature. The number 20 comes with or without a W, depending on whether it is being used to denote a cold or hot viscosity grade. The document SAE J300 defines the viscometrics related to these grades.

The ratings are performed by testing the flow of the oil at 40 °C and again at 100 °C (using kinematic viscosity, the kinematic viscosity is essentially the amount of time, in centistokes, that it takes for a specified volume of the lubricant to flow through a fixed diameter orifice at a given temperature).

Not much help but interesting..