Fork Oil Help

Before I add fork oil to my forks, do I need to change the existing oil to the brand that I am adding?

humm, i just changed my level, i was wondering the same but on another post about this subject, some said yes some said no,so while i had them down i just changed it altogether and also switched to mobile-one synthetic atf, and man what a difference!!!jimbo

I wouldnt recommend using ATF in your forks. we have tried this before, and it works OK, but the weight is around 10-12, which is way too thick. It needs 5 weight. It makes your valving very slow. A friend of mine has ATF in his forks, and everytime you jump it, the damping is so slow it pitches the front end of the bike high. I ould just spend a little bit more on fork oil, it isnt that expenisve.


well it works for me and a lot of other people, i use it and if you choose not too thats cool but it darn sure made a difference in my forks, and the synthetic weight is 7.5 ,maybe regular atf is 10-12 dunno,one of the shock builders on the board uses nothing but atf, so go figure. jimbo

I'm not taking sides on this one, but here's my thought process.

As an engineer, I'm cursed to approach things from a logical point of view. And any time someone says, "hey, you know that oil which is designed specifically for your forks? Well it works ok, but this oil which is designed specifically for transmissions works better" I have to wonder what the trade off is. There must be a difference and it would be interesting to see what it is.

That said, if you want to use ATF then have fun, but I don't think that you can possibly go wrong using oil specifically designed for the forks. Just my $.02... or maybe $.01. :)

JOHN,THANK YOUR SIR!!! i'm not one to just dump "snake oil" in anything. i did my research and saw the facts thus my decision to use ATF, granted it only has been in there for a week but first time out the change was dramatic for me anyway. My forks are totally stock, the oil in them i dumped was clean and clear but the level was too low for me so i rasied it and re-filled with the red-stuff...i'm happy. thnaks jimbo

Over the last few months I have come to the conclusion that proper fork performance is based on only one thing - cartridge pressure.

Meaning that when you strike a bump, pressure in the cartridge tube increases and is then bled off via the collection of valving on both ends of the tube.

When we modify our shim stacks, (or turn the clickers) we are essentially shifting a curve that represents the amount of pressure and the associated release rate.

So...a thicker oil slows the rate of the compression rod speed because it's harder for it to flow past the valving. The same pressure is present, but the bleed off rate is lowered.

See the difference?

Therefore you get a magical smoother ride with the thicker ATF oil.

However, certain applications, usually those involving very very high rates of pressure gains, (supercross, high speed desert...etc) require that rapid increases in cartridge tube pressures get bled at a very fast rate. They simply have to recover much quicker.

This is where the thicker oil fails to perform, as noted in the earlier post.

The other consideration is that when any oil breaks down from use, it loses its viscosity. The greater the initial viscosity, the more dramatic the break down cycle.

Do I think you should use ATF? Sure. It's convenience, cheap and covers up most performance issues.

If you race seriously or at high speeds, get down to the 3wt stuff.


Mobil 1 ATF,

Now there is a good topic.....

Ridepate is correct, the weight is 7.5

We tend to live in a "packaged society" if you will, where we get "accustomed" to go by whatever the label says....if you would have told me a couple of years ago that Mobil 1 ATF transmission fluid works good in forks, I would scoffed at the idea.

The truth of the matter is that the engineers at Mobil worked with MX-TECH on this project a few years ago.

There are 11 MX-TECH associates in the U.S and 4 overseas using this fluid with excellent results. Like I said , I would have scoffed at the idea a couple of years ago, but when I see a customers forks and shock come back a year later for servicing and see how good the fluid looks, I am definately sold.

Take Care, John

[ February 26, 2002: Message edited by: John Curea ]

Therefore you get a magical smoother ride with the thicker ATF oil

I'm sold :):D:D

Ridepate, the reason your old oil was clear is because the contaminants settle at the bottom of the cartidge. They're still in there, believe me.

mx-tech mixes ATF, 50/50 with another Mobil product to reduce overall viscosity.


It does the job, dont get me wrong, but suspension is all personal preference, and I personally like thinner oil (lower weight), so that is probably why I did not care for the ATF. I know it will not hurt anything, but, I choose not to run it. I wasnt putting it down, or saying your going to mess your forks up by running it, I just expressed my opinion, and I failed to realize that not all people like the lower weight oil and suspension set up like I do. So do what you want, and whatever suits you better. I am sorry if I offended anyone.


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