ATF is probably not a bad alternative as it has plenty of anti wear additives and should be shear stable.
It’s probably higher quality than most so called dedicated fork oils.
It’s probably higher quality than most so called dedicated fork oils.
Thank you, this sort of info is exactly what I was looking for.In my experience, the items aside from viscosity, that were considered during formulating fork oils were these, in this order:
1. Low shear
2. Low friction
3. Wear resistance
4. Anti-foam
5. Anti-oxidation
So in your experience how would these compare to something like a mid quality synthetic engine oil (maybe Mobil1) or more modern synthetic ATF (thinking something generic like maybe Castrol Transmax or similar)? Particularly as far as sheer, anti foam, and anti oxidation go?Anti-foam and anti-oxidation are both very important, but they are just so dang easy to incorporate into the formula, it didn't require any effort with regard to formulation. The shear, friction, and wear resistance is where you might see differences from brand to brand.
As @KrisZ mentioned, the wear resistance is nice, but the parts that experience are meant to be changed out anyway. So you may see longer life of those parts with a better formulated product.
Friction and "stiction" you might feel a difference, most probably won't though.
Shear stability is one that will almost definitely vary from high quality to low quality products. Formulating in shear stability costs $$$. No way around it.
The other thing to keep in mind is that fork oil, and fork performance in general, is completely subjective and the only aspect that riders feel from the oil is the effects from the viscosity.
Regarding stiction, most of it is from the seals and the dust boot, not from the internal workings of the fork. I always grease them before installation and the stiction is minimal.
If you install them dry, you will probably have a lot of stiction.
So in your experience how would these compare to something like a mid quality synthetic engine oil (maybe Mobil1) or more modern synthetic ATF (thinking something generic like maybe Castrol Transmax or similar)? Particularly as far as sheer, anti foam, and anti oxidation go?
I know you don't want to consider viscosity, but simply put, and engine oil's low temp viscosity will be really high. You'd probably have to compare it to a "30W" fork oil at least. Besides that, an engine oil like Mobil 1 probably won't have the level of shear stability you'd want to see. A motorcycle specific engine oil should be more shear stable, but your usually looking at even thicker viscosities, then.
ATF would be a much closer comparison, and people have been using ATF for decades with reasonable success.
With regard to your comment about wear resistance being a factor for your costs. Ask the manufacturers for data. Ask them if they have coefficient of friction and wear data for "4-ball wear" and "Falex pin and vee block" tests. (Before anyone jumps down my throat about them not being real world tests, I KNOW. They are simply some basic wear tests that a lot of manufacturers might already have the data on hand; and they at least give some idea of the tribological characteristics of the fluid.)
Viscosity index would seem important for fork oil unless you want damping force to change radically with temperature. That suggests to me that a good synthetic oil.
What is the viscosity index of ATF compared with fork oil ?
The problem with this that for most street motorcycles fork oil temp doesnt seem to have that wide of a range of temps. Forks are out front and have a relatively big surface area. My own testing with an IR thermometer on several different street motorcycles has shown that even as much as 10-15F above ambient is rare. Considering most street motorcycles are ridden in a fairly constrained range of ambient temps, Viscosity Index just doesn't seem that important for fork oil.
The oil in a monoshock in the rear is a different story, but that is a different conversation.
@SuperSalad Have you ever seen fork oil get blended to twice the wear resistance of an ATF?
Also, someone should point out the significant difference and importance of foaming between common man PCMO vs hydraulic oils.