Use ATF for fork oil??

[Bugslayer]

I've been looking for information in regard's to changing fork seal's. (yes, I've got a bad seal on my left fork.) When I googled it, I came across more than a few people using automatic transmission fluid in their fork's instead of fork oil. From what I've read, this was common practice until not too long ago. Even Honda shop manual's called for filling fork's with ATF. Anyone else ever heard of this?

[Patrick]

Its common.. ATF is 7.5 weight..

[Bugslayer]

Dang, I've never heard of that.... Guess I need to get out more. 

[woefman]

7.5 wt is little thin in my book but yes iv'e heard of such a thing using it.

I've used Synthetic power steering fluid as well 10 wt

if you upgraded your suspension springs  this may not be to thin only you can decide.

In short .... two things happen in our forks 1. compression dampening ( springs) and
2. Rebound dampening (fluid wt)

[woefman]

Here are my thoughts and they may be just thoughts ....

Reason I do not like ATF for Fork Fluid is most ATF is High Detergent Oil.

If you ever messed with Forks you find the old Oil has a stench to it and Black.

It gets it's Color from the Aluminum Forks.

These Damper Rod fork systems over time tend to beat up the forks a bit Slight Metal Shavings is common.

when these mix with the oil it contaminates it. Could be the Aluminum SHavings added to the oil makes sort of a wet sandpaper type effect. So in my mind you would be better served with Reg Fork Oil, High Grade Fork Oil  or Synthetic.

Such as a Synthetic Power steering fluid . Rather then a High Detergent TRanny Fluid.

But then again that is just me. I certainly would not Flame someone on this board if they chose to use it
Just expressing my reasoning.

Also I would like to add something to my First  Post on this .

I CHanged my GL1800 Suspension for Progressive front and rear.
I added 15 wt Fork oil from Honda.
My thinking was My bike is mostly in Arizona HEat so the heavier the better.

Well Turns out It is too thick.

Remember the Fluid is the Rebound Dampening for our type of suspension.

[Gryphon Rider]

The manual specifies fork oil.  I put 15 weight in mine and find it a little too firm for my liking, especially in cold weather when the forks hardly move for small bumps.

[quexpress]

I've been looking for information in regard's to changing fork seal's. (yes, I've got a bad seal on my left fork.) When I googled it, I came across more than a few people using automatic transmission fluid in their fork's instead of fork oil. From what I've read, this was common practice until not too long ago. Even Honda shop manual's called for filling fork's with ATF. Anyone else ever heard of this?

Have been running mine with ATF for the past 2 seasons. I like it. 

[mirion]

We build transmission test equipment and the only seal materials we use are Urethane and Viton. Most neoprenes as well as rubber swell up when exposed to ATF over in our experience.

[auditray2007]

Are there seals in the damper rod itself?

[jdp]

You can use ATF in suspension or any hydraulic but it's better to use fork oil in forks, motor oil in motors, power steering fluid in power steering, with all the synthetic stuff out there better to use the correct product, the only reason some use ATF and other fluids is the cost, it's cheaper.

[auditray2007]

Bump

[WintrSol]

As was pointed out in another thread (can't remember who posted), back when ATF was the standard, it didn't have all the additives it does now. Modern ATF just isn't great for fork seals, because of this.

[auditray2007]

Does anybody know if there are seals in the damper rod itself?

[WintrSol]

No seals in either the damper or rebound rod - at least, none that are replaceable.

[PAVALKER]

When changing out fork springs and seals on an 02 VTX 1800 and then my previous Valkyrie, they had thinner tranny fluid on one side and gear oil on the other.   I used aMSOIL fork oil afterwards.  Found it interesting tho.

[Paladin528]

ATF is about a 7 weight oil.  Fork oil usually starts around a 10 weight.  I up mine by 10 to a 20 weight because I am a heavier rider and I find it stiffens the damping a bit which I like

[98valk]

http://www.peterverdone.com/archive/lowspeed.htm  big list of suspension oils also
Low Speed Damping, Suspension Oils.

DO NOT GO BY LABELED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.

Suspension oil is labeled by weight because consumers are used to thinking of oil (ie. motor oil & gear oil) in these terms. The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require. Another point of confusion is that motor oils and gear oils are rated for viscosity on the SAE scale at different temperatures, leading to similar viscosity oils having very different ratings. SAE J300 is used to define engine oils, while SAE J306 is used to define drive line (gear) and chassis lubricants.

The Viscosity Index is very important in a suspension oil. “The viscosity index (V.I.) of an oil is a number that indicates the effect of temperature changes on  the  viscosity  of  the  oil.  A  low  V.I.  signifies a  relatively  large  change  of  viscosity  with  changes of  temperature.  In  other  words,  the  oil  becomes extremely thin at high temperatures and extremely thick at low temperatures. On the other hand, a high  V.I.  signifies  relatively  little  change  in viscosity  over  a  wide  temperature  range.” So specifically with regard to suspension, the greater the VI, the more consistent the damping will be over a large temp change.