Micky V
Junior Member
1978 SR500
Posts: 43
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Post by Micky V on Sept 29, 2008 5:16:45 GMT -5
Hi guys I have a question about what fork oil to use in my SR. I have some new Ikon heavy springs, cartridge emulators, seals, and tubes. Now allI need is the lube! I'm going for 15 weight oil and have heard that you can use engine oil is this true? If so does it do a good job?  Thanks for your help Mick V |
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Post by miker on Sept 30, 2008 10:14:41 GMT -5
Fork oil is supposed to have different additives than engine oil - makes sense, it's a totally different environment, temp, etc. and often doesn't get changed for years either. For the little bit you have to put in (and how long it lasts), why not get something good - I got Bel-Ray.
miker
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Post by solo2racr on Sept 30, 2008 10:46:15 GMT -5
I also read where the viscosity ratings are different as well. Something like 10-40 engine oil was equivalent to 70wt fork oil.
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Post by G Man on Sept 30, 2008 11:53:07 GMT -5
See this thread, some useful info: Click HereG Man |
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Post by gcrank1 on Aug 19, 2023 15:59:10 GMT -5
Fork oils do not translate well in the old, Nominal, engine oil 'weight' thing, nor is there a standard for them to formulated to, each manufacturer mixes their own blend of snake oil, etc. and throws a 'rating' on the container. This is fine if you stick within the fork/shock oils of the brand but no good at all if what is available at time of need is another product; ie one companies 5w could be another's 2.5w or 7.5w, etc.
The old 'damper rod' forks were pretty happy with atf on the 'light' end and the thicker/heavier engine oils, that is, they did 'ok'. They werent much past a butter churn system. We are far beyond that now with the cartridge forks and rebuildable shocks.
The somewhat 'new' method of comparing the flow characteristics for these hydraulic units is the 'cSt' rating. It is based on how fast a fluid moves through a 1mm hole, a numerical designation and much more precise than the old 'weight' thing. The charts are readily available online. Knowing where you start with X fork fluid's cSt number will allow you to incrementally move through the product list to change up or down to adjust compression and/or rebound.
Pardon the pun, but It Is Slick!
Note that fork/shock fluids are heavy on anti-foaming (anti-cavitation) agents and synthetics are a good thing.
A recent '81 SR fork drain, flush and refill had me starting with a bit more than the book quantity at 7(US) oz. of what would equate to about a '10w' of many brands. I know the cSt and can adjust up or down for the fork action I want to address. I can also fine tune a bit with quantity, but beyond a certain point there be dragons. I advise you use the recommended quantity until you feel like playing wizard.
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