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Message started by chiguy on 09/06/13 at 18:21:13

Title: Suggestions for fork oil
Post by chiguy on 09/06/13 at 18:21:13

I'm replacing a set of bent fork tubes with an un-bent set (thanks again, @LANCER). I need to add fork oil and I see that the recommended oil is "SAE 15 fork oil". I'm assuming I'll be able to get some at the local bike shop tomorrow (Saturday), but I'm wondering what options I might have if they don't have any in stock (I'm impatient). I've seen a tiny bit of information various places about using ATF. But it appears that you need to be careful to get the right stuff so the viscosity is appropriate and there are no additives to affect the seal or cause any corrosion.

I should mention that I'm not looking to change the ride characteristics of the bike, so if I can get the SAE 15 fork oil tomorrow, I'll do just that.

Thanks!

Title: Re: Suggestions for fork oil
Post by Serowbot on 09/06/13 at 19:45:27

A veteran Guzzi owner friend of mine, that also owns a Savage swears by ATF...
He says it's right about 13wt... and works real well...
I think it's Honda that recommends it in their manuals...

So, I wouldn't be afraid to try it...

Title: Re: Suggestions for fork oil
Post by WD on 09/07/13 at 05:05:44

Fork oil is just Dex3 ATF w/o the red dye added. Basically.

Type F is a bit thicker than Dex3, but can eat certain seal materials.

Dex6 is super thin, pretty much guaranteed to eat the seals, and is extremely expensive.

Be it Dex3, Type F or fork oil (BelRay brand is the best quality)... it's just a light machine oil, anti-foaming agents, and detergent. Fork oil has more oil than it has detergent, ATF has several times the detergent load of fork oil.

I've had Dex3 in my 98 Savage since at least 2007. Next time I feel like changing the oil, I'll probably use straight 40 weight motor oil. Can't stand front end dive, my biggest complaint with both hydraulic forks and lightweight oils used in them. My very tired Honda forks are getting 85W gear oil.

Title: Re: Suggestions for fork oil
Post by apache snow on 09/07/13 at 06:57:01

The specifications for a good Dexron III fluid generally show a 7.0 to 7.75 cSt Kinematic Viscosity (at 100 C) and a 40 C viscosity of 35 cSt. Flash points are about 367 F, pour points are -60 F, and sulfur is 2200 ppm with phosphorus being 620 ppm. The SUS viscosities are 17,500 cP at -40 F and 1,350 SUS for -10 F.

Here is the chemistry for an ATF such as Dexron III:
(Average additive concentration by wt.% taken from seven (7) different additive packages)

Phosphorous - 0.3% AW additive
Zinc - 0.23% AW additive, anti-oxidant as ZDDP
Nitrogen - 0.9% AW additive
Boron - 0.16% Detergent and AW additive
Calcium - 0.05% Detergent/Dispersant, tbn base chemistry
Magnesium - 0.05% Detergent and base chemistry
Sulfur - 0.55% FM and AW
Barium - various% used as particlate control

The calcium and magnesium need not be as strong in ATF as in IC engines, because these dispersant/detergents don't have to work so hard removing (cleaning) the carbonaceous deposits and sludge created by blowby.

DexVI is also much improved in the area of shear stability.

For a mineral-based Dexron III, the fluid may start out at 7.5 cST and shear down to 4.5 cSt within 30k miles.

For DexronVI, the fluid starts out at 6.0 cSt and may shear down to say 5.7 cSt.

The reason for the improved shear stability is due to two pieces of chemistry:

1. Some formulators use improved and highly stable VII polymers;
2. others use the new HM polymer esters not considered as VII chemistry.

Title: Re: Suggestions for fork oil
Post by ToesNose on 09/07/13 at 13:02:58

Way to just make me feel stupid reading that Apache Snow ;D