ATF in Forks?

Status
Not open for further replies.
Joined
Dec 28, 2016
Messages
2,892
Location
MURICA
So I have seen many online threads about using ATF(or PS fluid) in motorcycle forks.

Question is, I have quite a few types of ATF laying around, can it be any ATF? Or rather stick to fork oil.

What's the take of BITOG about using ATF in fork?
 
The front forks on a motorcycle are an integral part of how the vehicle preforms under steering and braking inputs. They have valving inside designed to meter a specific fluid during these maneuvers. Changing form the OE specified fluid to a fluid that they are not designed for is very dangerous. The seals may not be designed to hold ATF, PS fluid, baby oil, olive oil, or whatever. On a car if you have a from shock failure its bad but on a bike its catastrophic especially if it fails at a high stress load such as entering a turn under braking. If it was me I would only use a the fluid recommended by the OE manufacturer, saving a few bucks is not worth your life.
 
Originally Posted By: Gimpy1
The front forks on a motorcycle are an integral part of how the vehicle preforms under steering and braking inputs. They have valving inside designed to meter a specific fluid during these maneuvers. Changing form the OE specified fluid to a fluid that they are not designed for is very dangerous. The seals may not be designed to hold ATF, PS fluid, baby oil, olive oil, or whatever. On a car if you have a from shock failure its bad but on a bike its catastrophic especially if it fails at a high stress load such as entering a turn under braking. If it was me I would only use a the fluid recommended by the OE manufacturer, saving a few bucks is not worth your life.


I hear you, will stick to OEM fluid.
 
It depends on the type of forks you have, old damping rod style or the more modern cartridge forks. Damping rod forks typically use a heavier grade fluid of around SAE20 which in fact is in the range of most regular ATF's (not the LV variety) than the cartridge types which require like 5-10. That's the biggest factor. Sure, specialized fork oil claims to have all sorts of unique additives that make it better suited, my opinion is that's mostly marketing but opinion vary on that.

That said, I've used ATF for years in my Harley forks which are damper rod forks. Works great. There is nothing in there that is bad for seals, bushings or anything else. It's well developed fluid, and the application is pretty simple. I'd guess it would be too heavy for a cartridge fork but I've never tried it.

BTW the weights you see listed on fork oil bottles mean very little, look at the cSt specs if you want to compare. People take that label as fine science and get in endless debates as to why one is harsh and another isn't, when in fact it's not even an apples to apples comparison.
 
Give it a try.I doubt most forks get worked hard enough to matter most of the time.Worked fine with the old conventional type for me.
 
Originally Posted By: LotI
I like how the KLR forks work with DexIII

It’s too thick for the VFR, too stiff.


I have a VFR too
smile.gif


Do you use Honda SS8 fluid or something different?
 
Nice bike, the VFR's. Always wanted one.

Those bikes have cartridge forks don't they? If that's the case, it would stand to reason they may like something lighter. Honda/Showa SS8 is almost identical in viscosity to DexIII and many other ATF's which are more suited to damper rod forks. I assume that KLR has cartridges, so I guess whatever works works! In any event, back to your original question, ATF certainly will do no harm.

The main reason I use ATF isn't even cost, although it is about half the cost, it's more because I try to avoid keeping special purpose lubes laying around unless there's a noticeable performance improvement. I use ATF in the forks, shocks, and primary on my Harley, plus transmission and power steering on some cars. Shoot, I even use it with acetone as a penetrant on seized up bolts. So.......it's a convenience thing that also happens to perform equal to or better than more expensive specialty alternatives in those applications.
 
Last edited:
Originally Posted By: maverickfhs
Originally Posted By: LotI
I like how the KLR forks work with DexIII

It’s too thick for the VFR, too stiff.


I have a VFR too
smile.gif


Do you use Honda SS8 fluid or something different?

Currently running Redline Lightweight as it’s close in cSt to SS8 but has amazing an amazing VI
 
Originally Posted By: Silk
ATF is all I ever use, although sometimes will use a hydraulic oil like ISO32, 46 etc.


Just curious, what's the weight of hydraulic oil? Is it similar to hydraulic jack oil or something?
 
I've tried ATF, seems like fork oil works better all the way around. "Better" is a function of the bike in question and how you ride it, of course. But even with Progressive Suspension springs preloaded to my riding style, I didn't like the ATF a lot. It certainly helped with the extension speed, putting the front wheel on the ground faster, but I never liked the compression rate.

An uneven, unpredictable, or too fast rate of loading or unloading in a curve can be unnerving, this changes your effective trail, and the rear suspension can even get involved in the dance, which can be sickening.

If you push into corners hard or ride on somewhat rough roads I think regular fork oil works better, and it does come in different viscosity which can help you fine-tune to your style.

If you don't push the bike hard it doesn't matter.
 
saying "fork oil" is like saying "race gas"

you really dont understand what you are talking about.

there are close to a dozen different versions and weights of "fork oil" and vp racing fuels sells at least 2 dozen
versions of "race gas".

mobil 1 atf CAN be used in a motorcycle fork...or shock...oil. so can "hydralic fluid". so can 7.5wt mineral oil.
and so can a 5wt non-newtonian oil...errr fluid.
 
Originally Posted By: sunruh
saying "fork oil" is like saying "race gas"

you really dont understand what you are talking about.

there are close to a dozen different versions and weights of "fork oil" and vp racing fuels sells at least 2 dozen
versions of "race gas".

mobil 1 atf CAN be used in a motorcycle fork...or shock...oil. so can "hydralic fluid". so can 7.5wt mineral oil.
and so can a 5wt non-newtonian oil...errr fluid.


Thank you sunruh, I do have some M1 ATF laying around. But I'll stick to fork oil after hearing some feedback.
 
Originally Posted By: Gimpy1
The front forks on a motorcycle are an integral part of how the vehicle preforms under steering and braking inputs. They have valving inside designed to meter a specific fluid during these maneuvers. Changing form the OE specified fluid to a fluid that they are not designed for is very dangerous. The seals may not be designed to hold ATF, PS fluid, baby oil, olive oil, or whatever. On a car if you have a from shock failure its bad but on a bike its catastrophic especially if it fails at a high stress load such as entering a turn under braking. If it was me I would only use a the fluid recommended by the OE manufacturer, saving a few bucks is not worth your life.


I don't believe this at all. Yes, if you have anti-dive forks - maybe ...

If you have standard valved forks, not at all. The MFG does not know how you ride, or what you weigh, so they go by averages. If you are small and light, or super beefy, you are outside the norm for their fluid. If you ride hard and dive into corners under heavy braking, you are outside their norms. If you ride dirt or dual sport, you must adjust for the terrain and the ambient air temps. The fluid that works well in the snow zone will be way to light for riding in AZ in the summer ...

One of the things a rider/owner must be able to do is to tune the suspension for the ride at hand. Swap shocks, change pre-loads, change dampening, etc. If you can't do that, you are not much of a rider/tuner ... Your behind will not be happy. Your braking will not be sure. Your passengers will not be happy or comfortable ...

ATF (Dextron III) is a great choice for some situations. Tractor hydraulic fluid is good for others. Bel_Ray fork oils come in a range of viscosity from 5 to 50 ... Your choice
smile.gif


I've drained the garbage low-bid fork oil out of countless motorcycles and installed other fluid to get a desired result. Many went straight to ATF. Some went to 7.5 fork oil. Some to 10, a few to 20. Other than short track Ceriani's we never ran anything stiffer than 20. Short track bikes might go to 30. But a side car bike might go to 40 ... Depends on loads, rider style, and expected terrain ...
 
Last edited:
Originally Posted By: BrocLuno
Originally Posted By: Gimpy1
The front forks on a motorcycle are an integral part of how the vehicle preforms under steering and braking inputs. They have valving inside designed to meter a specific fluid during these maneuvers. Changing form the OE specified fluid to a fluid that they are not designed for is very dangerous. The seals may not be designed to hold ATF, PS fluid, baby oil, olive oil, or whatever. On a car if you have a from shock failure its bad but on a bike its catastrophic especially if it fails at a high stress load such as entering a turn under braking. If it was me I would only use a the fluid recommended by the OE manufacturer, saving a few bucks is not worth your life.


I don't believe this at all. Yes, if you have anti-dive forks - maybe ...

If you have standard valved forks, not at all. The MFG does not know how you ride, or what you weigh, so they go by averages. If you are small and light, or super beefy, you are outside the norm for their fluid. If you ride hard and dive into corners under heavy braking, you are outside their norms. If you ride dirt or dual sport, you must adjust for the terrain and the ambient air temps. The fluid that works well in the snow zone will be way to light for riding in AZ in the summer ...

One of the things a rider/owner must be able to do is to tune the suspension for the ride at hand. Swap shocks, change pre-loads, change dampening, etc. If you can't do that, you are not much of a rider/tuner ... Your behind will not be happy. Your braking will not be sure. Your passengers will not be happy or comfortable ...

ATF (Dextron III) is a great choice for some situations. Tractor hydraulic fluid is good for others. Bel_Ray fork oils come in a range of viscosity from 5 to 50 ... Your choice
smile.gif


I've drained the garbage low-bid fork oil out of countless motorcycles and installed other fluid to get a desired result. Many went straight to ATF. Some went to 7.5 fork oil. Some to 10, a few to 20. Other than short track Ceriani's we never ran anything stiffer than 20. Short track bikes might go to 30. But a side car bike might go to 40 ... Depends on loads, rider style, and expected terrain ...


Thanks for your detailed response and help.

Now curious, can I use M1 ATF for normal street riding and being an average weight or healthy BMI?
 
Status
Not open for further replies.
Back
Top