Strut Cartridge Replacement - Dampening Oil

[Mike]

Dampening oil added to strut housing between cartridge and housing:

I recently had to change the shocks in my Z, and the previous owner

had changed the shocks about 3-5 years before, and he had not put any

oil in the shaft the strut cartridge had gone in. The Cartridge over

time had fused to the strut most likely do to excessive heat, and a

lack of lubrication. As a result, this made this out to be a very

unpleasant experience for me after being in there for a while the

cartridge was stuck in the shaft to where it was VERY VERY difficult

to come out. In fact one of the four never came out.. even after the

strut had been heated with a torch (which was necessary on the others

to remove them) it never came out... I was really stuck because the

original strut was now damaged in trying to remove this cartridge, and

where was I going to get another one when I was getting this work done

with a friend, out of town, on the weekend??

I sooooooo lucked out that the Nissan dealer had an original brand new

strut tower that you could no longer order sitting on the shelf

because it was ordered 5 years before, and was never picked up. This

was the original style with a non cartridge style shock already in it,

but since I was using the same Tokico shock on the other 4, just a

cartridge version it didn't matter.. I can just put in a cartridge

style in there next time it needs to be changed.

In short.. I really recommend lubeing the strut cartridges

>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<

On 5/1/00, 6:31:15 PM, Mike Gholson <mtg@mgdesign.net> wrote regarding RE:

<240z-club> Rear Struts:

> -- Group Message from Mike Gholson <mtg@mgdesign.net> --

> It is my understanding that you shouldn't need to add any

> oil with MODERN strut cartridges.

> The manual recommends it because the older struts depended

> on the oil for heat dissipation and lubrication of the shaft.

> Again, this is MY understanding. I could be totally off.

> But, I didn't add any oil to my new Tokico Illumina's because

> of this advice.

> [m]

> > -----Original Message-----

> > From: Panos A. Rontos [maimailto:Prontos@gte.net]

> > Sent: Saturday, April 29, 2000 11:02 AM

> > To: 240z internet club

> > Subject: <240z-club> Rear Struts

> >

> >

> > -- Group Message from "Panos A. Rontos" <prontos@gte.net> --

> >

> > I know that this has been covered; however, my computer has

> > gone through at

> > least one rebuild since then and I have lost the message. The Datsun

> > service manual states I should pour 400cc of geniune Nissan

> > strut oil or

> > equalivant into the case for cooling. Any suggestions as to

> > what to use?

> --------------------------------------------------------------

[Mike]

-- Group Message from "Pete Paraska" <pparaska@tidalwave.net> --

Mike Gholson <mtg@mgdesign.net> wrote:

>Is this really a concern if you purchase a high-end strut

>cartridge? I figure that their engineering methods would

>lessen this possiblity.

Strut cartridges and shocks convert mechanical energy to heat.

The amount of heat generated is proportional to the damping.

Damping is the mechanical energy involved and has to do with

the force (related to the Illumina's setting), velocity and

translation of the two ends of the "damper".

I don't have handy any numbers on what the amount or rate of

conversion of this heat is for different driving conditions,

but it's not inconsequential. I wouldn't bet that air alone

is enough to convect the heat away quick enough from the strut

cartridge body to the strut tube during spirited driving. The

amount of connection between the strut tube and cartridge is

minimal for conduction heat transfer.

Any racers here want to chime in?

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[Mike]

> Any racers here want to chime in?

OK, chiming in...

> I wouldn't bet that air alone

> is enough to convect the heat away quick enough from the strut

> cartridge body to the strut tube during spirited driving. The

> amount of connection between the strut tube and cartridge is

> minimal for conduction heat transfer.

FYI... my Tokico Illuminas are in the struts dry. Purely a maintenance,

cleanliness issue.

Shocks heating up and loosing effectiveness is not really an issue in autox

because you have time between runs for everything to cool down. Tire

overheating will occur way before you have any issues with the shocks. At

the MSA autox last Saturday I did 6 back-to-back 46 second runs and greasy

tires ended my fun, not the shocks getting hot. Also, I've run 20 and 30

minute track sessions at Buttonwillow and WSR and hot shocks were never a

concern.

But, Peter is right from a theoretical point of view and if I was building a

rally 240Z I would definately do everything I could to cool the shocks.

----------

John Coffey

johncof@veriomail.com

[Mike]

-- Group Message from Rob Harville <RobH@Insynq.com> --

I would think shock overheating would be much more of an issue in off-road

racing like the Baja series. They have MUCH more suspension travel and at

high speeds. The tire heating isn't as much of an issue because of the

loose "track" surface. This is why they run remote-reservoir shocks with a

very high oil capacity w/ coolers on the reservoirs. I've never heard of

this being an issue with NASCAR, CART or INDY. Even with autox, there just

isn't enough constant full-travel articulation.

[Mike]

> How about every-day drivers? Or, weekend excursions along

> the coastal highways?

If I can't heat these things up at an autox or a track like Buttonwillow

then I don't think a street driver can do it, unless they are driving fast

over the pot-holed roads of Detroit. You would need a lot of low frequency,

large travel or high frequency, short travel inputs to start generating

heat. You really aren't much of that on the street unless the road are

really bumpy. Also, have you driven Pacific Coast Highway lately? You'll

spend most of your time going < 25mph behind a Mini-Winnie watching two

brats smear food on the back window while Dad drifts into oncoming traffic

at each corner.

Now, I WOULD put some oil in there to avoid the corrosion issues mentioned

in a previous post.

----------

John Coffey

johncof@veriomail.com

[Mike]

-- Group Message from RICHARD SCHULZE <richard@eoa.com> --

Dear Group:

>-- Group Message from "Pete Paraska" <pparaska@tidalwave.net> --

>I don't have handy any numbers on what the amount or rate of

>conversion of this heat is for different driving conditions,

>but it's not inconsequential.

Pete hit the nail on the head! The energy generation from shocks is not

inconsequential. As a Mechanic, I always put a little oil in the strut

housing when replacing inserts. Now I find that many Auto manufacturers

are designing and making Hybrid cars that are gas and electric. They

gain efficiency by recouping wasted energy. One of the prime waist

sources is the cars kinetic energy which is converted into brake heat

every time you stop. On the hybrids, when you hit the brake pedal, a

generator is linked to the drive line which drags the car down while

producing electricity to charge a battery pack. One of the biggest

secondary sources of wasted energy is shock absorber dampening. The

makers of Hybrids are designing shocks that are like linear motors which

get their dampening from electro magnetic repulsion while generating

electricity for the batteries. There is a significant amount of energy

coming from these shock and good heat dissipation will extend seal life.

Richard Schulze

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[bpilati]

I wanted to make sure this thread wasn't a one man show.