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Old 03-29-2020, 04:54 PM   #1
pjdeb
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Default Shock oil

What do you use for shock oil in the original lever type shocks?
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Old 03-29-2020, 05:08 PM   #2
fundytides
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Default Re: Shock oil

Just bought some from Bratton's
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Old 03-29-2020, 05:10 PM   #3
Ted Duke
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Default Re: Shock oil

I asked an old-timer that once and he said, "Shocks, what shocks?"
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Old 03-29-2020, 05:51 PM   #4
Kevin in NJ
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Default Re: Shock oil

Not an easy question to answer properly.

I was taught that the action of the original shocks should be very hard to turn in one direction and a bit easier in the other direction with the original lever.

A couple of years ago I was able to build a quick test rig loosely based on details from someone with the original KRW test fixture. The weighted arm was supposed to take like 15 seconds to sweep though a number of degrees.

I have a number of very slightly worn original shocks. With some shock oil I had they seems fairly stiff. The one shock that was slightly more worn was a bit easier. Now by wear I am talking a couple to a few thou. Yes they are fairly nice shocks. Of course I do not have a match set of 4 but I want working over correct.

Well I put my 'KRW' test rig on the shock. Well it took like 5 seconds or less to go stop to stop. WAYYYYYY faster then spec!!!!

So my take on all of this...

I know really hard to turn by hand shocks do make the car handle OK. Keep in mind I will think nothing of going 60 MPH on shocks that meet my old 'spec'.

Slight amounts of wear can have profound effects on how well the shocks work.

I need to experiment with heavier oils. I have been using both hydraulic jack oil and motor cycle shock oils. I need to figure out what would be thicker and still work well as shock oil. I am open to suggestions.

I have been underestimating how to properly judge shocks.

I will build a good copy of the KRW tester for better testing.

That being said, why are your shocks dry??

Have you actually checked that the shocks work?

Shocks are notorious for being hard to seal. Also many that are slightly too worn are put into service. Is there any play at the center?
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Old 03-29-2020, 06:08 PM   #5
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Default Re: Shock oil

Originals used castor oil or glycerin. If these have been overhauled then the person performing the overhaul should fill you in. If you are refilling, you may have to try to gain access to whatever is in them now. A very low viscosity mineral oil may be in there. Mineral oil and castor oil have distinct odor to them. Glycerin doesn't have much odor but it has a sweet taste if it's not too dirty or old to bother checking. They used to have different shaped filler caps on the later 30s shocks so you could tell what was in them.
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Old 03-29-2020, 06:17 PM   #6
Gary WA
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Default Re: Shock oil

Ive used 20wt hydraulic jack oil!
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Old 03-29-2020, 07:18 PM   #7
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Default Re: Shock oil

Interesting. I am in the process of changing the front spring and wanted to check the front shocks as I have them disconnected. They do seem to operate as Les' book says.....harder to push down that lift up......60/40. I have not opened the fill plug yet. Will do that tomorrow. Just wanted to know in case I needed to get some. I take it from the comments that whatever is in there (unknown) should not be mixed ....... so I guess that means do not top it off if all it needs is a little?
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Old 03-30-2020, 03:13 AM   #8
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Default Re: Shock oil

Glycerine or glycerol (same thing) mixes with water. It absorbs water from the atmosphere and then corrodes iron and steel. In the 60's I had shocks that were filled with old glycerine which had turned brown and thickened. I cannot imagine after 60 more years there are any unseized houdaille shocks using glycerine, unless someone has religiously flushed and renewed the glycerine.
Being water soluble it will not mix with oils, hence the reason to check the contents. Easiest is to get some on a stick and then see if it washes off with water. I have about a dozen old shocks that had glycerine in them. They are all ruined with corrosion now. All are dismantled and I bought 8 Stipe shocks for two cars because the old houdailles were too far gone to fix without making new rotors, and re- sleeving the bodies. Far too much work for me to contemplate until I retire.
I have not heard of castor oil being used. Shocks get very hot on rough roads and castor oil gels when heated and then cooled. That is why racing engines using it had to be drained immediately after a race.
"Air blown " castor oil is a very thick form and used in old fashioned non-hardening gasket cements and modern rubber greases. Another disadvantage in a shock absorber.
Stipe shocks call for synthetic 20 weight shock oil if I recall correctly. Worn shocks can use 90 or 140 weight oil to compensate for wear, in a suck it and see exercise. This helps slow leakage too.
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Last edited by SAJ; 03-30-2020 at 03:18 AM. Reason: Added data on oils
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Old 03-30-2020, 11:42 AM   #9
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Default Re: Shock oil

Houdaille shock oil was originally castor oil based and I'm not sure if it had alcohol mixed 10% or not. Early airplane engines used castor oil as a lubricant so it wasn't uncommon. When Ford started using them, the "shock oil" preferred was glycerin with 10% alcohol mix. In the mid 1930s they used castor oil base, glycerin base, and mineral base fluids depending on the subcontractor that made them and the filler cap shapes would let you know what was to be used. Since these shocks were not really intended to be overhauled by the average repair shop, I don't think they worried too much about how long they would last. You can still find a number of commercial "shock oil" cans from the early Ford era and many of them don't list what the proprietary contents is. If you had a Ford, you were supposed to use Ford shock fluid or at least fluid made for Houdaille type shocks.

Now days, some of the rebuilders recommend a light viscosity synthetic motor oil for a fluid. The only seal in there was usually a leather packing. The most concerning thing was of mixing of fluids. Some don't mix at all and others will congeal when improperly mixed. It's always a crap shoot about what to use on one you are not intimately familiar with.
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Old 03-30-2020, 01:36 PM   #10
Kevin in NJ
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Default Re: Shock oil

I have attached a PDF of an article in one of the Model A magazines.

The article explains the fluids used over time. That should answer some questions.
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File Type: pdf 2014-06-21 18-26.pdf (1.65 MB, 37 views)
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