Fork Oil Viscosity

[CarlS]

I have been researching for oil as I my upgrade my XC's front suspension. I am not a suspension expert by any means. I came across a discussion about fork oil viscosity and an interesting chart.

For example the Tiger 800 manual specifies Oil Grade -- Showa SS 8 (which I have discovered is 'something-like' an SAE 10 viscosity). When it comes to fork oil, the SAE viscosities may be too broad of a measuring stick -- one SAE viscosity number can cover a range of viscosities.

Accurate fork-oil viscosity is usually measured by a more accurate scale: cSt - centiStokes or SSU - Saybolt Seconds Universal. If you want your T-800 forks to operate as Triumph intended, then you (probably?) need to use that same oil. If you want to change fork characteristics? -- you may be able to do that, too?

Here is the chart:
http://mahonkin.com/~milktree/motorcycles/fork-oil.html

Also, see the chart's listing of VI (viscosity index) -- that's the number that indicates the oil's resistance to viscosity change with temperature -- usually, the higher the number the better-- the "perfect" oil would not change viscosity with temperature.

 

[Rocky]

Wow, that's very interesting!
I didn't realize that simple fork oil isn't quite so simple and that chart made my eyes glaze over.
Good stuff

 

[CarlS]

I thought I understood fork oil viscosity. My research confused me!

 

[dazco]

Well, I'm too impatient to look at that and really figure out whats what. But i can tell you this much. My bike came with 10W and i put 15w in it and it improved very notably. Later on i changed it before i needed to because i was putting the chrome fork legs on, and i couldn't find 15w so i figured i'd use 10w thinking it had been a while and maybe it wasn't that big a deal after all. Well, wrong. Stiffer forks really make the bike handle better and don't dive so much when braking. I'll be putting 15 back in soon. Should have done it long ago but living conditions make it tought to work on the bike.

 

[boofhead]

I used 12 1/2 in my America to stiffen up the front end , it worked great
A "push bike "mechanic on another forum told me that thicker oil in the forks does nothing , Based on his many years of working on pushbikes