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Shock fluid weight


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#1 HKSZ

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Posted 21 August 2014 - 11:33 AM

Has anyone got a recommendation for the old style shock weight ie 5w 10w 15w 20w? in a rally car.

Pedders did a wet leg conversion, revalve, coilover on my rally struts 5 years ago and it has been a real good thing. But with the long 20- 30km rally stages now the front end has become floaty, took it back to pedders and the bloke who built them doesn't work any longer and knowone knows anything about them.

Which fork oil is best? 5w is Motox, so I'm thinking lightweight bike USD forks
                          up to 20w which is crusier/harley

I've rebuilt one leg myself and used 15w Motul fork oil, struggle to pull or push the chrome tube by hand now



#2 dat2kman

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Posted 21 August 2014 - 12:06 PM

Always used single 10 weight oil.
Singer sewing machine oil was good.
Floatyness comes from worn holes in the seals, they open up a bit, and oil becomes equivalent to a 0 weight.

Some played with combo of ATF and 10, or ATF and 20, but 20 would blow out seals on hard ( dirt rally) stuff.
Maybe OK on fast road.
Biggest issue is current spec oils foaming up, once foamed/aerated, its useless.

#3 HKSZ

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Posted 21 August 2014 - 04:06 PM

Cheers, I'll run it this weekend on an autocross. The struts had leaked out oil, very little left probably 100ml and very dirty/thin. For some reason the inner tube had soft rubber wrapped around it? so I guesstimated it needed 320ml of fluid.

Replacing oil and seals has cost $25 so it's worth having a go. The one mob who would rebuild the shocks wanted $500

#4 Cozza

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Posted 21 August 2014 - 09:02 PM

I rebuilt the wet legs of my 1600 and used 10w motorcycle fork oil, but couldn't find replacement seals at the time, where did you get them from?
Mine were moderately stiff to compress by hand but seem about right for a standard street car, which is what I was trying to achieve. The 1600 is still a work in progress so I haven't got to do many k's in it yet.

Sounds like you have everything sorted, but I have attached the Factory Service Manual page discussing volume and weight of oil for the 240z.
290ml of Nisseki Shock Absorber Oil A-2 (not sure what A-2 is equivalent to). It also makes a mention that the volume of fluid directly affects damping power.
Its interesting the 1600 FSM suggests 290ml for SSS models, 300ml for all other sedans and 325ml for wagons Nisseki Shock Absorber Oil A-1. I figured the more oil would increase damping power but it seems it's the other way round.

Let us know what you find after your event.
Mick

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#5 HKSZ

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Posted 03 September 2014 - 08:47 PM

I've had a chance to run the zed on some rough gravel, better but I'm still not happy the rebound now looks to be slow.
Might go from the 15w down to 5w next.

Will soon have to invest in some REAL rally suspension, some of the state rounds are like goat trails

#6 dat2kman

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Posted 03 September 2014 - 09:03 PM

As above, the 10W is the go. 5 will be too "quick" through the valving and will foem up..
But yes, some decent inserts would be better. KYB are a good all-rpunder, and less costly than Bilsteins.

#7 HKSZ

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Posted 04 September 2014 - 12:37 AM


OK I'll go the 10w all round, I do have a set of HDT 40mm Billies but pretty sure they don't fit the 51mm 240z strut.

Jason I've got 200lb kings in the rear and 220lb pedders prog in the front does that sound right for gravel, thinking of tossing the pedders for single rate 220lb cos the top 5 coils stack flat.

#8 dat2kman

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Posted 04 September 2014 - 08:46 AM

Yes, ditch the progressive, their initial softness will def make the shock heat up quickly.
If you already have single rate 220's, pop those in, you want supple suspension, not hard.

One possibility with those Bilsteins, have a look at turning up a bit of alloy tube of correct OD/ID to slip inside strut, to hold shock in centre.
The top gland nut may need some form of washer, in alloy welded to top of the sleeve?
Common trick also, race tape some packing washers to bottom of strut insert so that top nut screws down tight.

Watch that it does not bottom out! Quadrant in Melbourne are the Billie agents, they can rebuild these.
For dirt work you want the wheel to fall as rapidly into a pothole, but on rebound, you want it to come up quickly, but not throw the car upwards violently.

I have a set of the big shaft Bilsteins in the race Z, they are very good. Would not use a oil only insert, if buying them.




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