Valve springs in forks thread

**Padmei** · 3rd December 2009, 19:06

Thanks for the feedback.
Bugger now it's another $50 to experiment with.

What oil do you guys use with your expensivators? I've been using castrol fork oil 5 ISO15. It says on the back sae viscosity ranges vary widely and the iso relates to oil vis at 40degrees.

So does this mean the oil gets 'thicker' at 40 degrees & doesn't flow as well or the other way around & get too thin?

How long would it take to get up to temp & I assume the more they're working over rough ground the hotter they'll get with friction?

Should I just fill the buggers with more oil? What would happen - just seem harsher as WW explained above?

hmmm

**NordieBoy** · 3rd December 2009, 20:11

It would only feel harsher approching full travel.
I'm using Spectro 5w or something cheap from the Suzuki shop.

**Woodman** · 3rd December 2009, 20:51

Originally Posted by Padmei

Thanks for the feedback.
Bugger now it's another $50 to experiment with.

What oil do you guys use with your expensivators? I've been using castrol fork oil 5 ISO15. It says on the back sae viscosity ranges vary widely and the iso relates to oil vis at 40degrees.

So does this mean the oil gets 'thicker' at 40 degrees & doesn't flow as well or the other way around & get too thin?

How long would it take to get up to temp & I assume the more they're working over rough ground the hotter they'll get with friction?

Should I just fill the buggers with more oil? What would happen - just seem harsher as WW explained above?

hmmm

I used castrol 5w as well. Slightly off topic but viscosity works like this:
Oil does not get thicker as it gets hotter, basically the higher the number the thicker it will be at a given temperature, but never thicker than when cold.When there is a multigrade engine oil e.g.10w40 the first number relates to the relative thickness when it is cold so a 10w will flow faster at start up than a 15w. The second number relates to the thickness at operating temperature so a 30w will be thinner than a 40w when an engine is running at the same temperature. so a 40w offers better protection than a 30w at operating temperature cos its thicker.

Woner what would happen if you put a multigrade oil in your forks.

**NordieBoy** · 3rd December 2009, 20:58

Originally Posted by Woodman

Woner what would happen if you put a multigrade oil in your forks.

You'd want a 10w5 reverse multigrade oil

Firmer damping when you're hammering it and it's hotter. More supple when you slow down...

**dino3310** · 3rd December 2009, 21:00

cool now i know, always wondered what the relationship between the 2 were

**warewolf** · 3rd December 2009, 21:30

Originally Posted by NordieBoy

You'd want a 10w5 reverse multigrade oil

Firmer damping when you're hammering it and it's hotter. More supple when you slow down...

You sure 'bout that? The numbers are cold-W-hot, surely you want 5W10.

Yes, there are multi-grade oils; IIRC I tried a 15w20 in the Triumph years ago, but it was just too damn heavy - felt like straight 20 when cold (15 is standard).

Also Castrol suggest you can mix'n'match ratings to give fine control, eg half 5 half 10 will give 7.5.

Hmmm interesting on the Castrol 5w being 'light'. That's what I'm using now, and lately I've found my forks much less harsh, much less firm, and have been able to set the clickers at close to factory settings. I used to have the clickers backed off a long way to try to get some compliance. Now I'm thinking the 'lighter' 5W Castrol suits my style.

If you look at the chart I quoted earlier, Spectro's 5W (what I used to use) has a centistoke rating at the high end for 5Ws, at 21.60, just shy of Ohlins #10. Maxima 5W is 15.90, down near Ohlins #5 at 16.50, the lower end. 15-ish to 20+ is more than 33% increase - that's a huge difference!! It's quite foreseeable that the Castrol 5W is down near 15.00.