Fork oil

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Went to the surgery this morning. Medico asked me if I was over 50kg. Had no idea but I knew I was eight and half stone! Problem solved!
 
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I use 20 wt oil - tried 30 wt and it is too stiff for road surfaces, even two up. Filling the legs can be a messy business and lose you your carefully measured volumes. You need to be able to move the sliders a little so its best to take the wheel and the mudguard off, then roll a piece of index card and insert into the top of the stanchion to allow a decent amount of oil to be poured. Then judicious jiggling and a break for a coffee gets all the oil in the fork and not on the floor.
 
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It is tedious. I was blessed enough to do it twice in a month. Once for seal replacement & again for stanchions/seals when seals only failed.
 

Lineslinger

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Went to the surgery this morning. Medico asked me if I was over 50kg. Had no idea but I knew I was eight and half stone! Problem solved!
I grew up in the sixties...hell any self respecting Dead Head knew that a key or Kilo was gold in name and could be acquired in Acapulco and it actually equated to 2.2 pounds...that's weight, not British currency, before all the stems and seeds were cleaned out to make tea. And, it was directly related to stone or stoned depending on consumption....
all clear?o_O:)

Guess what I found in and old socket set that had not been opened in 20 years?!?
 
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I learned metric weights at the very same university. Once the smoke cleared I realized it wasn't doing much to enhance my future so I stopped. Only then did I find the future had become the past, but.....I had a whole bunch of fun and trouble of mine own device.....and....my Norton till death us do part, and...….I flogged it a bit today, and.....it liked it! With 5 fl. oz. US ea. tube 10w-30 held steady with no remorse.
 

illf8ed

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Currency aside, I have always been happy with 150cc per fork leg of any good quality purpose made fork oil of 30wt viscosity. My understanding of multi weight engine oil is the viscosity is the same as the low number. So 10w30 has 10 weight viscosity with engine protection to 30wt. My experimenting with 20wt fork oil ended with not enough damping. 10wt seems like it would have almost no damping. Also since forks don’t require warm up protection as would an engine, why use multi weight oil at all?
 

Lineslinger

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166-8581_A.jpg View attachment 10649
View attachment 10649 I saw that piece on Atlas.com which took me to the science site. I'll bet, back in their day, they didn't put those guys in jail for possession.

I researched fork oil here and I talked to a variety of riders at a bike night along with a recommendation from a local shop that helped me immensely.
I used the above after fork overhaul......
 

lcrken

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For what it's worth, this is the data sheet the factory sent me back in the early '70s when I asked about specs for the 1971 Commando Production Racer that I had just acquired. I've included both pages, just for completeness. Page 2 shows 180 cc of CRI30 Castrol. CRI30 was 30 weight motor oil, not 30 weight fork oil. The fork internals on the PR are the same as on the road Commandos. I experimented a bit with different oils, and ended up using 30 weight fork oil at most tracks. I suspect that might be a bit harsh for street use. On my street Commandos, I mostly just used the factory recommendation, 150 cc of 10-30 motor oil.

Page 1 1200.jpg


Page 2 1200.jpg


vintage-empty-castrol-motor-oil-cri30.jpg


Ken
 
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xbacksideslider

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So, what’s the conversion factor of fork oil to motor oil?

Is 10wt fork oil the same as 10wt motor oil?

And, since cold 10-40wt motor oil has 10wt viscosity, will it dampen the same as cold 10wt fork oil?
 

rvich

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I use hydraulic oil. ISO 32 is equal to 10 wt oil. ISO 46 is about 15 wt oil and ISO 68 is equal to 20 wt. And yes I know I could buy oil specifically made for motorcycle forks. I choose not to shop in the local motorcycle shop and if you lived here you wouldn't either.

Regarding units of measure, when I was a teen and doing my first major tour on my Commando I went into Canada. They still sold gasoline by the gallon back then. I was stunned at how good my gas mileage was while in BC because I was too stupid to realize they were selling Imperial gallons! (1.2 U.S. gallons.)
 
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So, what’s the conversion factor of fork oil to motor oil?

Is 10wt fork oil the same as 10wt motor oil?

And, since cold 10-40wt motor oil has 10wt viscosity, will it dampen the same as cold 10wt fork oil?
Fork oil viscosity seems all over the place vs what is on the label. I will post a list tomorrow.
 

gortnipper

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I used to use 30w fork oil, but after a fork service which included replacing the alloy damper caps, the damping increased quite a lot and I now use 15 weight.
 

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