fork oil

[ssls6]

I was thinking about fork oils today and wondered why a 5w-20 synthetic oil wouldn't make for a great fork oil? The viscosity of most fork oil is measured at 40C (on the bottle) and at that temperature a 5w-20 should be close to a 10w?

When cold, would it not perform better? How about resistance to fade on really rough roads?

 

[bruce381]

most fork oils are less than 5wt to 10wt a 5/20 would be to thick even cold and would not have the high amount of AF required to control foaming.
but the price is right and may give you the feel you want no harm to try.
bruce

 

[Jaybird]

Mobil1 Synthetic ATF would be a better choice.
I think it is equivilent to a 7wt. fork specific oil.

 

[ssls6]

I believe they measure fork oil viscosity at 40C. At 40C, a 10wt fork oil and a 5w/20 motor oil should be close.

Which will fight oxidation better? Shock fade from temperature build-up? Moisture?

Why would Mobil ATF be a better choice? What attributes does it have other than being a 7wt?

 

[msparks]

quote:

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Originally posted by ssls6:
I believe they measure fork oil viscosity at 40C. At 40C, a 10wt fork oil and a 5w/20 motor oil should be close.

Which will fight oxidation better? Shock fade from temperature build-up? Moisture?

Why would Mobil ATF be a better choice? What attributes does it have other than being a 7wt?

---

Why reinvent the wheel?

Amsoil makes a great full synthetic shock oil that has a very high viscosity index. Meaning that it works in a very wide temperature range. It has special seal conditioners to keep seals pliable as well.

Comes in a 5wt and 10 wt. If you want a 7wt. mix the two.

 

[ssls6]

quote:

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Why reinvent the wheel?

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Why not?

What makes AMSOIL's fork oil special? I've never seen a VOA on fork oil or ATF for that matter. Why would a 0w-20 PAO not make for a better fork oil?

 

[John Ulrich]

quote:

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Originally posted by Jaybird:
Mobil1 Synthetic ATF would be a better choice.

---

Don't go there!!! I tried it once and it was so slick it literally bubbled out of the forks as they traveled.
Replaced with 7W fork oil and it took a few days for the Mobil 1 to wipe itself off the seals. That was 4 years ago and it has not leaked since!

Love Mobil 1 in everthing else.

Later,
JU

 

[satterfi]

Fork oil is designed to have excellent anti-foam properties at temperatures that a fork will experience.

How much anti-foam is in motor oil and does it work as well at relatively low temps?

Most fork oil has a lot of seal conditioners in them. They survive the relatively low temps you see in a fork.

How does motor oil compare?

Mongolian bike riders take used motor oil from broken down Lada's and use it for fork oil. If that's ok by you, then go for it.

 

[msparks]

quote:

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Originally posted by ssls6:

quote:

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Why reinvent the wheel?

---

Why not?

What makes AMSOIL's fork oil special? I've never seen a VOA on fork oil or ATF for that matter. Why would a 0w-20 PAO not make for a better fork oil?

---

The high Viscosity Index provides shear protection over a wide temperature range.

Prevents fading over high temperatures like in racing applications

Great anti-foam properties which also helps with control and keeps the shock feeling more consistant.

Extra seal conditioners keep the seals soft and pliable helping them last longer and preventing leaks from starting.

That's about what makes it so special.

 

[XS650]

What spec governs hydraulic oil like used in MC forks. I keep hearing about SAE 5, 7,5, 10 etc, but can't find out what the spec is.

The engine oil spec, J300, doesn't go that low.

 

[qadsan]

quote:

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Originally posted by XS650:
What spec governs hydraulic oil like used in MC forks. I keep hearing about SAE 5, 7,5, 10 etc, but can't find out what the spec is.

The engine oil spec, J300, doesn't go that low.

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Exactly! The quasi-SAE numbers listed on suspension oils are not standardized and that's why I use the ISO scale instead. I've tested various suspension oils in the past and found some 2.5wt's more viscious than 5wt's and some 5wt's more viscious than 7.5wt's at room and working temperatures. Those quasi-SAE numbers listed on fork oils can be very misleading when comparing one brand of fork oil against another because there is no standard for some of those weights. You've got to be careful even when comparing a 5wt against another 5wt simply because SAE 5wt is a 'range' of viscosities. ISO numbers are more specific and will ensure more consistant results.

 

[Cujet]

Actually, M1 ATF is a favorite among suspension techs. It has a fairly high VI and is considered to be equivalent to a 10W fork oil. I have used it in my Husqvarna 360 forks and shock with great results.

I also used it im my RZ350 forks with good results. Though it was a little thin for such an underdamped bike.

Chris

 

[KellyL]

I change my fork oil yearly and use ATF. I've had no problems. just becuase of how I ride, I mix the ATF with honda 10W fork oil and have had NO problems. It's a much better combo than the straight HD Screaming Chicken oil.

 

[DNS]

quote:

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Originally posted by John Ulrich:

quote:

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Originally posted by Jaybird:
Mobil1 Synthetic ATF would be a better choice.

---

Don't go there!!! I tried it once and it was so slick it literally bubbled out of the forks as they traveled.
Replaced with 7W fork oil and it took a few days for the Mobil 1 to wipe itself off the seals. That was 4 years ago and it has not leaked since!

Love Mobil 1 in everthing else.

Later,
JU

---

I'm using Mobil 1 in the forks of my Kawasai Voyager and it worrks very well. I know others that are using it with good results. None of have any seal leaks from it.

 

[qadsan]

Many of my older motorcycles had ATF specified as fork oil in their factory owners manuals. Mobil 1 synthetic ATF works quite well in some fork applications and it even works in shocks too, but for shocks there are better choices if you're really working the shock hard.

 

[Jaybird]

I asked a proffesional suspension builder about this subject the other day.
He stated that Mobil1 synATF was fine to use in both forks and shocks. He said that he would not hesitate to use it in a shock and it does very well in shocks, but he prefers a lighter weight fluid in the forks.

 

[KX 455]

Running Mobil 1 ATF, in the forks will cause a very stiff rebound,own experience. I had to back out(quicker)rebound to just about the end of the clickers.
Keith
"Let's just ride"

 

[David in Sugar Land]

For the Norton, Dextron ATF is known to be just dandy. I would say that any vintage bike, esp. of the Brit-iron variety, would do well. Others have opined that 5wt. does well.

Type F ATF (the one recommended for older Fords!) in primary chaincase is the other use of ATF in Norton Commandos. Just so you would know...

Adding to oil tank's Rotella is not recommended though! We like our Ro'tel straight outta the jug!