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post #1 of 17 (permalink) Old 05-24-2015, 11:21 PM Thread Starter
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Fork Oil Research

In trying to translate my '76 T140 owners manual recommendations on fork oil to current products, I thought I share the information found. Hopefully the extrapolations of the information are correct.

The owner's manual lists several specific AFT oils, a couple being Mobil ATF 210 and Castrol T.Q.F.
Information is still available on both these products which are type "F" or Ford spec trans oils. One opinion expressed was that Type F was basically a 20 weight motor oil base with additives and red dye and without friction modifiers.

The specs found on Mobil ATF 210 were: 8.5 viscosity @ 100 degrees C, 39 viscosity @ 40 C., Visc Index 196.
The Castrol TQF specs were 8.5 viscosity @ 100 degrees C, viscosity @ 40 C not listed, Visc Index 166.

The two products were similar except in the VI, which apparently indicates variability of viscosity within a temperature range, higher number being less variability.

One product that seems it may match up is Maxima Racing Fork oil in 15 weight which has 8.5 viscosity @ 100 C, VI 151.
The Maxima regular 15 weight fork oil also has a 8.5 viscosity @ 100 C and 47 @ 40 C, VI 151.
These look similar to the original ATFs seeming to indicate that a 15 weight fork oil may be in the general ball park of the original specs.
I didn't look into other brands but hopefully similar information is available.

That being said, one thing learned was that oil grade (weight, a misnomer?) is Not it's viscosity. A local dealer thought that 7 1/2 weight fork oil was about equal to AFT but it doesn't look that way from the comparisons above

To take the weight out of the picture, there are also a couple current synthetic ATFs, Amsoil and Redline, that are noted as "Racing" and referred to as type "F".
The Amsoil is listed as 7.1 viscosity @ 100C and 40 @ 40C.
The Redline is listed as 10 viscosity @ 100C and 54 @ 40C, a bit higher than the former.

To me it looks like a 15 weight fork oil, or perhaps a mix of 15 and 10wts may be a reasonable match to the ATF specified in the T140 manual, with the Amsoil Racing ATF an alternative.

Any supporting or contradictory information would be welcome.

Last edited by Beemie; 05-25-2015 at 01:38 AM.
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post #2 of 17 (permalink) Old 05-25-2015, 01:33 AM Thread Starter
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Here is a good comparison chart:
http://www.advrider.com/forums/showt...=286065&page=6

Unfortunately it doesn't cross reference ATF.
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post #3 of 17 (permalink) Old 05-27-2015, 09:47 AM
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Hi Beemie keeping in mind forks run cold meaning say 25-110f I did a drip test. Took some paper cups. Poked a pin hole in bottom & filled cup to a line about 3/4 full. Then counted how many seconds it took to drip into a lower cup to marked line about 1/4 from bottom.
I found most atf compares to 7.5w Belray fork oil with the drip test. Type F, DexronIII, Mercedes atf134, 5/40 synthetic motor oil were all quite close. I used atf134 because it's free to me.
I've checked the temp on many auto trans at work as some the level is set at 80c. On a summer day the trans will normally run near 100c which is of course is 220f.
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post #4 of 17 (permalink) Old 05-27-2015, 05:12 PM
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Originally Posted by TR7RVMan View Post
On a summer day the trans will normally run near 100c which is of course is 220f.
It was 212F when I went to school.
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post #5 of 17 (permalink) Old 05-28-2015, 02:01 PM Thread Starter
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drip test. Took some paper cups. Poked a pin hole in bottom & filled cup to a line about 3/4 full. Then counted how many seconds it took to drip into a lower cup to marked line about 1/4 from bottom. Don
Interesting. I'd need to think about whether that was a legit viscosity test or a test of another property of the fluids. Going down stairs to dig out the fluid dynamics book from school.
You say "about" 3.4 full.
First thoughts are that different depths as well as different densities would produce different pressures at the bottom of the cup.

Last edited by Beemie; 05-28-2015 at 02:04 PM.
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post #6 of 17 (permalink) Old 05-28-2015, 08:54 PM
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The forks on motorcycles, are hydraulic actuated. (Except Harley Davidson's "Springer" type forks, that are no longer marketed.)

This means you can use a hydraulic oil/fluid. I would pick a premium oil that has all the additives that are needed. Don't just get an "R & O" (rust & oxidation inhibited fluid).

You'll want anti-foaming, water shedding, & other properties.

My recommendation would be to use 1 (or mix 2) of Shell's Tellus oils. You'll find them in many different viscosity grades.

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post #7 of 17 (permalink) Old 05-29-2015, 02:48 AM
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Sorry, 220 was a boo boo by my fingers...
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post #8 of 17 (permalink) Old 05-29-2015, 09:54 AM Thread Starter
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I ride at 75 degrees and up and as noted before I can find viscosity numbers for the original spec'd ATF and current fork oils at 40C which is 104F to be between 10 and 15 weight Maxima fork oil.

The VI is fairly high meaning there shouldn't be a big change in viscosity in a small temperature change going from 104F to say 80F so I think I'm on the right track, atleast for my usage range.

But I managed to get a more specifically technically trained fellow involved for another opinion.
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post #9 of 17 (permalink) Old 05-29-2015, 09:55 AM Thread Starter
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It was 212F when I went to school.
Ya but Celcius or Centigrade?
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post #10 of 17 (permalink) Old 05-29-2015, 09:57 AM Thread Starter
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Originally Posted by NORTY FLATZ View Post
My recommendation would be to use 1 (or mix 2) of Shell's Tellus oils. You'll find them in many different viscosity grades.
The exercise is to determine an equivalent weight to the original spec'd AFT, which by example is Shell ATF 210.
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