5W-30 instead of 10W for fork oil?

[GSX1000E]

If the dust has settled, I run straight 5W-20 synthetic MOTOR OIL in these forks with '79 1000L front springs. It also has S&W 13.5" rear shocks and an 18" rear rim.
It rides close to ideal for me. (synthetic motor oil is full of anti-foaming additives BTW.)

[Gorminrider]

Fork fluid is Designed for forks. ATF+motoroil is not. It is more trouble but given that some original manuals include it, it has to be good enough at the least.
I've wondered why mc manufacturers recommend the mix or even ATF by itself...I've yet to be satisfied by answers I've found, so, I'll speculate.

Today, I think it's because ATF is anti-foaming, good with heat and seals and a consistent viscosity throughout temperature ranges...loosely speaking "7w" I think.It's a hydraulic fluid of a type.
ATF survives in automatic transmissions for a long time.it is tough but does not suffer "combustion" products. ATF alone in forks seems to get dirty pretty quick..perhaps it doesn't hold dirt/water in suspension as well as motoroil.
Multigrade motor oil has detergents and extra lubrication and is probably better at suspending abrasive crap. But barring modern synthetics, is not touted as "anti-foaming".(ie:"detergents,additives?) Say a 10w30 =30 "weight" at 212F degrees. What it is when you pour it in your forks is something less but roughly speaking in an engine, it's supposed to get pumped to wearing surfaces quickly and "thins" to 10w at a pretty cold temperature.

I would think that mixing ATF+10w40 isn't going to change viscosity much in forks without knowing it's "thickness" at the middling temperatures.

Fork oil was available at motorcycle stores in the 70's and before. I distinctly remember changing fork seals on my cl350 with it then.

Someone somewhere suggested MC manufacturers suggested ATF+ motoroil because they figured 3rd world countries wouldn't have "proper" fork fluid. This idea supposes that automatic transmissions were common in the outback...? The same manufacturers are very specific about other things, which does not gybe with an outlook on maintenance in the "3rd world".

[Grimly]

Can anyone say how 5W-30/ATF blend would compare to 10W-30/ATF in front forks? I've got a whole bunch of new 5W-30 sitting here that's never going to be used for anything else (since I no longer own any cages).

Was wondering exactly that, myself. I have several litres of 5W-30 left over from bulk purchase that isn't much use in the bikes. Recalled using 10W-40 and 20W50 blended with ATF in the past, as per various manuals' recommendations and had good enough results, but never used 5W-30 for this.
Of course, I'm not a do-or-die racing type, so don't notice the miniscule differences that might show up.

Fork oil was available at motorcycle stores in the 70's and before. I distinctly remember changing fork seals on my cl350 with it then.

Someone somewhere suggested MC manufacturers suggested ATF+ motoroil because they figured 3rd world countries wouldn't have "proper" fork fluid. This idea supposes that automatic transmissions were common in the outback...? The same manufacturers are very specific about other things, which does not gybe with an outlook on maintenance in the "3rd world".

Speaking from direct experience, I can tell you ATF was more commonly available than specialised fork oil where I grew up and even when it became more readily available was usually only to be found in the motorcycle dealers', where it was priced beyond reason. This state of affairs only changed relatively recently.

[GSXR7ED]

Abrasive Feedback

I will look into your posts on 550 forks Pendulum, thank you. I wasn't looking to pi$$ anyone off. And I realize some here come off as very caustic. What I always have to remember is that everyone is here to help one another.

Bingo! Yes, some are sharp to answer questions--if you haven't seen it by now, bookmark this thread.

At the end of the day it's about valuable information provided.

Ed

[trippivot]

my bike has spectro fork oil in it.

respectfully, I would like to discuss suspension and getting a smoother ride - I am not a clown - nor clowning around. I happen to have an opinion - I work at a privateer motorcycle shop - that is how I feed my family. Giving out tips actually works against my professional bottom line - but since everyone considers themselves a motorcycle mechanic anyway, I might as well attempt elevate the understanding - lets move on.



Motorized bikes have not always had fluid telescopic fork suspension. -- can we agree about that? it is written it is documented.

ok airplanes had the first EVER telescopic fork suspension -- ok -- that technology applied to motor bikes when? .... ok now I am clowning around

what was the first type of oil used in hydro forks? pure whale oil - am I wrong? somebody stop me when I make a mistake


ok we probably use whatever we can get easily - and promise ourselves that we will change it quickly.

[Pete's GS]

As for using automotive oil in your forks, it's okay as the factory manual for the GS750 called for a 50-50 blend of 10W-30 and ATF. As for 5W-30 ATF instead of 10W-30, I imagine the change would like running 5W fork oil. Kind of thin.

[Grimly]

what was the first type of oil used in hydro forks? pure whale oil - am I wrong?

Probably true. The Japanese were still using fish and whale oil in the 60s and 70s.
Alas, poor Moby, I knew him well...
This explains the unholy stink of fork oil the first time you changed it.

[Griffin]

Fork oil is readily available, relatively inexpensive, easy to install/change out for a different viscosity, and one variable is removed (mixing different fluids) when experimenting with different weights to achieve a desired result.

I can buy a bottle of Spectro, Bel-Ray, Maxima, Silkolene, Castrol, PJ1, or many other brands I can't think of off the top of my head that has enough to do a couple pairs of forks for $10-$15. Buy three different weights of the same brand, experiment all you want, and you will achieve your desired results for an investment of about $30. Now you can spend a whopping $5-$8 per year to keep it that way.

I don't argue that you can use different fluids in your forks, but I can't understand why you would? The manuals also say to use 10w-40 automotive oil for our engines. Who here still does that?