fork oil viscosity ?

[Speedy1959]

Ordered all the parts for my fork refurb from Fowlers (£137)!!

What viscosity of fork oil do you suggest?
My riding weight is about 100kg..
Oh and how much oil should I buy for both forks ??

Thanks in advance

[mlivkovich]

Changed oil on mine k2. I used 10w oil as I am 120 kg You will need cca 1.2 litre.

[Hooli]

That ^^

It's 576ml or something daft per leg, but it's more accurate to do via the air gap.

[Speedy1959]

Thank you both..
I will buy 2 litres of the 10W stuff

Thanks again

[T 24]

I use 10w.

[gsxbarmy]

5W oil is the recommended standard from Suzuki, and what the handbook recommends. Many use 10W, personally I preferred the 5W Castrol Synthetic Fork Oil, little dearer but works a lot "quicker" than normal oil, so good for roads that are not so smooth as the fork can react quicker to the bumps etc

https://www.ebay.co.uk/itm/Castrol-Synthetic-Motorcycle-Bike-Suspension-Fork-Oil-5W-500ml/142673285610?epid=15011414387&hash=item2137fd91ea:g:XW0AAOSwRE5acCsz

Putting 10W oil in will make the fork react slower. Practically its not the way to "adjust" your fork movement, use the recommended 5W oil and then use the adjusters on your forks to fine tune how you want them to work / work for your weight.

Oil/Air gap (the way to set them) is 108mm

[Andre]

Unlike motor oil, there is no viscosity standard for fork oil. Brand A's 10W is Brand B's 5W. If you want a apple-to-apple comparison you need to look at the viscositiy the oil has at 40°C (cSt@40°C). SUZUKI FORK OIL L01 (the one recommended in the Workshop Manual) has 15.50 cSt@40°C. As was suggested here, it is a 5W oil. Let's say you replace it with 10W from Castrol. Will that increase your damping? NO! The 10W from Castrol has only 15.00 cSt@40°C. To make matters even more complicated, the Castrol Synthetic Fork Oil 5W has 28 cSt@40°C and in 10W it is 42.00 The 7.5W Motorex Racing Fork Oil has 35.9 cSt@40°C while the 10W Silikolene Fork Oil has 34.90 cSt@40°C.

Here are a couple charts listing a bunch of fork oils and their cSt@40°C http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid http://mahonkin.com/~milktree/motorcycle/fork-oil.html

You need to check the manufacturers' data sheets to be sure not to get oranges instead of apples.

I am about 100kg and will put in a 22.7 cSt@40°C over the weekend. I expect to use a slightly stiffer compression/rebound setting over the standard settings. Will see how it goes.

A few good words from an experienced suspension guy on fork oil: https://www.youtube.com/watch?v=lXRxxmvBHCQ:

[mlivkovich]

Heavier oil will increase the effective damping, in other words the forks will move up and down a little slower and feel stiffer. Lighter weight oil will do the opposite, allowing the forks to move up and down faster and feel softer.
So, I am heavy and often have passenger and luggage and sometimes it is too heavy for my bike's suspension. With 10w oil I found that I can adjust damping and rebound to cope with extra weight. Not sure is it really a benefit using 10w oil but my feeling is that fork is stiffer.

[T 24]

And one more thing to mix your heads... 
Mineral base oils are MOSTLY more gentle to oil seals, but synthetic base oils CAN have additives for longer seal life

[mlivkovich]

And one more thing to mix your heads... 
Mineral base oils are MOSTLY more gentle to oil seals, but synthetic base oils CAN have additives for longer seal life

now we have one more thing to debate...

[seth]

Can you get blue and white oil

[mlivkovich]

I put candy blue 10w oil in my fork so it moves faster,  just like if I used 5w 

[shanered6]

I just use 10w in the left and 5w in the right ..... it just saves me having to decide !! 

[T 24]

Can you get blue and white oil

Blue and white is the fastest oil, but black oil is spoilt

[Speedy1959]

The way I ride I doubt I will nkotice any difference whatever grade I use..

I still say may 4 pots are way better than my 6 pots..