Gas vs. foam/oil shockies

[cleanskin]

hi lads, its time for me to buy some new shockies for the 75series and im not too sure on what too buy gas or oil shocks.... i dont do extreme 4bing more bush touring and chasing pigs up bush... can you give me your opions on whats best.Thanks

[Suspension Stuff]

hi lads, its time for me to buy some new shockies for the 75series and im not too sure on what too buy gas or oil shocks.... i dont do extreme 4bing more bush touring and chasing pigs up bush... can you give me your opions on whats best.Thanks

I think we should take each shock at its merits. There doesn't seem to be a clear winner, however I have had most experience with gas shocks and have had very good reliability with all the brands that I have used. Lovells, Dobinsons, EFS, Procomp. For most vehicles and applications I would suggest Lovells.

Some say that foam cell is theoretically better but some shocks have let them down. I think it boils down to the sum quality of all the components plus how they fit with each other.

Good luck
Shane

[joeblow]

look at the leading manufacturers...ie- kyb etc, you won't find any foam cell stuff there.

[me3@neuralfibre.com]

The idea of foam is to no have a gas space. The gas being a problem when the shock gets hot and the air foams the oil

I have yet to imagine a foam that doesn't leak some air, and doesn't fall apart after getting hot too many times.

Paul

[KiwiBacon]

There are several types of gas shock as well.

Gas emulsion, where the gas and oil share the same space. Then shocks which have the oil and gas seperated by a piston.

I run two pair of konis on my rig, fronts are emulsion twin tube (lets me revalve them). The rears are high pressure monotube with the pistons seperating the gas from the oil.

Easy way to tell. High pressure gas shocks self-extend. None of the others do.

[chimpboy]

AFAIK they are all "oil shocks", and gas, high pressure gas, foam, etc, are all there purely to keep the oil from foaming/frothing when the shock is working. It's the oil that does the actual work, even in a "gas" shock absorber. But... if you have high pressure gas it will lift the car (not much but a little) due to the added springiness.

Either way I agree with Shane, there are too many other variables that come into play besides the foam/gas question, like manufacturing quality, materials, etc, etc, so choosing the right one is never going to come down to a particular technology, it is going to come down to the specific make and model of shock.

[DIRTY ROCK STAR]

let the price decide i say....
best price on a reputable brand wins?

[Suspension Stuff]

The sole reason why there is gas or foam in a shock is so the oil has somewhere to go when it is displaced by the shaft of the shock. If you have no foam or gas then what chimpboy said.

Shane

[MightyMouse]

Shane's got it completey right - if the oil didn't expand when heated then none of this stuff would be necessary. The gas/foam etc role is to allow the oil to expand but not allow it to aerate which destroys its damping characteristics.

I prefer monotube gas shocks as I've never had a problem with them and their single wall design dissiapates heat quickly but a twin tube ( which many foam cell unts are ) may be a bit more dint resistant but tend to run a bit hotter.

There are lots of other factors as well to be considered e.g some consider single tube gas to be initiall harsher as they damp small movement more effectively than other types but this is a very personal choice.

Good brand shocks are expensive from all manufacturers but personally I'm inclined to stick with the big reputation brands like Bilstein, and Koni.
There's a lot of engineering and development in a high quality shock.

[KiwiBacon]

Shane's got it completey right - if the oil didn't expand when heated then none of this stuff would be necessary.

Don't forget the volume of the shaft entering and leaving the body.

[bazzle]

The sole reason why there is gas or foam in a shock is so the oil has somewhere to go when it is displaced by the shaft of the shock. If you have no foam or gas then what chimpboy said.

Shane

Err Not quite...

Keeping this simple............
1.Oil aerates when it gets forced thru the valve assemblies, the pressure of the gas compresses the size of the air bubbles alllowing the oil to perform its job effectively.
2.There is always a small amount of bubbles in the oil. As it gets hot the bubbles expand reducing shocks performance... the gas pressure acting on the oil reduces the bubble size as above..

Foam cell type just use the foam as a spring to hold pressure down on oil similar as very low pressure gas

Bazzle

[Suspension Stuff]

With the introduction of air you get problems that you have to solve. Because of the shaft going in and out we need air and a solution to stpo the interaction as you say.

There is a lot more to it I would like to learn, hopefully some guru can post up.

Shane

[cleanskin]

Thanks alot guys, im gunna go out n buy some new shockies now! Cheers.

[joeblow]

don't forget, gas shocks can recover from heat, but once a foam cell is damaged from too much heat it stays that way.