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View Full Version : oil Vs gas shocks - whats the difference?



THRSTY
20-05-02, 06:50 PM
ok, im just curious what the main differences are between oil and gas filled shocks, apart from one having gas, and the other having oil in it (for all you smart asses :p)

eg, life expectancy, handling, rebound, etc etc

the shocks in particular are koni gas and koni oil shocks.

recommendations etc?

thanks

X605
20-05-02, 07:13 PM
Firstly oil and gas shocks are the same in design except for the gas....
The gas in gas shocks in pressurized nitrogen.
The only use of the gas is to keep the oil cooler for a longer time and therefore keep the shocks valve rate more constant ...

normally as the shock works the oil heats up and as it does so it thins out, with the oil being pressurized it takes longer to heat up and therefore stays thicker longer

the pressurization has no other "real" effects to the shocker other than make it extend when there is no load apon it

Kinks
20-05-02, 07:44 PM
yep, standard oil shocks are just filled with oil, when they heat up the oil gets foamy with little gas bubbles and the shock rate changes. gas shocks have nitrogen inside them to exert pressure on the oil and prevent it from foaming up.

X605
20-05-02, 08:30 PM
and there is also foam cell shocks too!!!
which are used in off road and rally cars.. they are designed to really cut down on foaming of the oil

THRSTY
20-05-02, 11:09 PM
ahhh, that sheds new light on the subject

thanks all those who replied, much appreciated.


so how long does it take oil shocks to change their rate (i realise you cant really say this as it depends on many many things, but just an approximate time on normal roads driving both hard and normal eg a few minutes, a few hours, etc)

X605
20-05-02, 11:24 PM
well as you susgested its very had to say......

but say you were really giving it to the car on a rough road or through the hills the oil would basicly start "going off" after a few mins..... were as on a smooth freeway they might not even think of "going off"

Also you might of see some shocks that have remote canisters on them (v8 supercars, DMT touring cars and some off road cars) these basicly are just a resavoir of oil (gas charged) that is hooked up to the shock.. the theory is more oil takes longer to heat up and therefore longer before it can "go off"

THRSTY
21-05-02, 01:43 AM
ok cool, cheers for that.

i knew that gas were better, but wasnt sure of the reasons why

why would koni make most of their shock types of this type if it is obviously this case. how affected does the rate get? can you really tell?

dont worry, last q, so no more pestering after this question :)

cheers buddy

tandy ass
21-05-02, 09:28 AM
I've also heard of shocks with an external oil cooler for the real exotic cars!

But its true, go feel your shocks after driving down a bumpy road, they get quite warm, at times I even wonder why they dont just put some fins on it to help dissipate the heat...

arti
21-05-02, 01:10 PM
Car is always lower with oil shocks as the pressurised gas shocks are always pushing the shaft up.

Cordia1
21-05-02, 07:19 PM
What about with lowering your car... if u have gas shocks can u still lower the car or does it affect the way the gas part works? I know with oil its usually fine as long as you dont go too far and hit the end (say on big bumps etc)

hotgemini
21-05-02, 07:24 PM
On most shocks as long as you aren't going to bottom out the shock and the damping rate is suitable, then you won't have any problem.

One area where you may strike dificulties is with shocks like the sensatrac which damps differently depending on where in the stroke you are, most other shocks the damping is only dependant on piston velocity.

X605
21-05-02, 11:10 PM
Car is always lower with oil shocks as the pressurised gas shocks are always pushing the shaft up.

this really isent a concern the pressure of the shock in most cases isnt engough to raise the car at all.. in the casae where they do "hold up" the car its at most only 5mm or so



One area where you may strike dificulties is with shocks like the sensatrac which damps differently depending on where in the stroke you are, most other shocks the damping is only dependant on piston velocity.

Ive seen a few sensor tracks that have been cut open to see whats going on inside and i can say the major prob with sensortracks is the "soft zone" is created from simple oil bypass channels in the wall of the shock , where the valve would sit at normal ride hight.....
on std hight cars the shock sits in this 10-15mm zone (approx) and when the valve travels beyond this zone (out of the bypass gallerys) and in larger bumps in the road, the shock rate is increase as the all the oil is now going throughthe vavle.


therefore if you use a sensor trac on a lowered or rased car it is in its harder setting to start with and can acttually get softer on the biger bumps in the road instead of firmer..



there are some changing rate shock out there that use a 2 stage valve instead of bypass galleris and the 2 stage shock will work on cars that are lowerered, rasied and std high as long as the shouck isnt bottoming out or in the case of rasied cars (ppppft) is extending fully, but keep in mind thease type of shocks are really desgined for extra comfprt not performance