Ohlins front spring, advise

I've recently bought 2 ohlins springs .80 spring rate from ebay.
The seller advised me to use 10w fork oil, rider sag between 35 - 48 and static sag between 25 - 30 mm. What is the sag more exactly? How can I achieve those values?
About the fork oil: now I have a 20W castrol fork oil, made only ~3000 km with it so I wouldn't change it. Also there is a plastic spacer (probably fitted by the ex owner) under de fork caps, I guess to increase preload.
So what do you guys recommend about the fork oil, sag and the spacer?

Thanks!

BTW: on the end of the forks there is this code written: "08657-80/L337".

[embee]

I have 0.85 springs in my SK1 and use 10W oil. The particular springs I used did not need spacers to get the right sag, but it depends on the actual spring design.

I guess you have used 20W to try to help the front suspension with the standard springs, which are quite low stiffness (0.709 if I recall), but this doesn't really solve the problem. Your springs will be a much better fix.

I would suggest you'll find 20W too stiff with the new springs. You can always try it of course, and if you feel it too harsh or overdamped them change it. It does depend on teh make of oil too, they are not all the same even with the same nominal rating.

So, if the suspension is to stiff, to little sag (below ~25) the solution is to remove the spacers? If the sag is to big (more then ~30) then I should increase the preload with more spacers?
Yes, I used the 20w oil to help the old springs. The oil is from castrol, witch I guess is not as good as WP or hyperpro for example.
Can I mix it with a 10w or even a 5w oil to reduce it's weight? I's short on budget, so I wouldn't like to replace it
Is there any way of measuring if the corrent fork oil is OK?

Thanks, Alex

You should go for the rider sag. You cannot get static sag and rider sag both at the design value unless you are the design weight. You may be, but if you set the static sag and you are light or heavy, your rider sag will be wrong.

Accuracy is difficult because of stiction. You can overcome this to a degree by sitting on the bike then taking your weight off the front so it rises slightly then gently move back to riding position - no pumping. It should compress a little again. Take this measure. Then get your weight right over the front so it compresses a bit and transfer gently back to riding position. It should rise slightly. Take this measure. If there was no stiction, these would be the same. The theory is that the reading you want is the average of these two. It might be easier if a friend lifts and compresses the front for you so long as they do it gently. That makes three of you - rider, holder upper and suspension weighter.

Do this with the spacer out. If you can get the right results with the pre-load adjusters then you don't need it.

I don't think it makes sense to look for an exact setting. It depends on your style as much as anything. And I suspect it takes a Valentino Rossi to notice anything but fairly significant differences anyway.