Outer Limits 4x4 Board

Hi there, i have set of tuff dog shocks, (hydraulic i suppose you call them)
and a set of bilstein gas shocks. I am running the tuff dog but wondering if i would be better off with the gas ones. Do gas shocks help force better articulation by forcing the wheel towards the ground.
Cheers.

You wont notice that effect (gas pushing down) but nice theory. The rebound from the springs is much faster than the gas cares to expand and the coil will still be pushing out against the shock.

Gas are a bit stiffer than oil/hydraulic and so you get a slightly sportier stiffer ride. Landrover/Rangie guys like the soft oil shocks. Toyota and Nissan guys tend to go the sportier gas shocks.

Foam Cell are stiffer again. They dont get as hot and when they do warm up they dont fade (go soft) like Hydraulic and gas do. Comp guys should run Foam Cell unless they have the multi valved or coil overs. I believe all adjustable shocks are hydraulic ... bottom the range in technology terms. Funny how comp guys choose the 4Way adjustables. I wouldn't run Hydraulic in a comp rig - Foam Cell for me all the way. Remote canister shocks are a step towards keeping gas shocks 4cool, but that's all they achieve.

By the way Nitrogen is about the cheapest, non combustable and easiest to get and manage gases and so almost all gas shocks are Nitrogen. Funny thing is some brands use "Nitro" as a marketing pitch.

As far as I know all current automotive dampers are hydraulic.

Foam/gas are simply ways of controlling aeration of the oil in the damper body . Plain old hydraulics cannot be completely filled as the oil expands when hot and have no method to control aeration and thus suffer under hard use.

Foam and gas are mechanisms to allow the oil space to be completely filled but allow for expansion into a foam filled or gas pressurised reservoir.

Foam seems to be a cheaper way of achieving a similar effect to gas, the ones I have seen are still coaxial construction and therefore don't dissipate heat as well as a monotube shock - but have a greater level of dint resistance.

Although to be fair good gas shocks use very high quality tube material and are difficult but not impossible to damage.

Plain Hydraulics tend to be the cheapest, with foam next and gas pressurised the most expensive.

The gas pressurisation certainly exerts a force ( try and fit one after its extended ) but due to the rebound damping its going to be very controlled and slow and compared with the usual spring rates will probably not be noticable.

Pretty much what Hobzee said.
All the gas does is keep the oil under pressure which helps stop the oil from aerating under harder working conditions. The faster the shock travels the hotter the oil gets, as it gets thinner it becomes more vulnerable to aerating. The gas pressure increases the the time it takes for the oil to aerate. This is known as fading. The bilstiens will perform better with constant high speed work and have a lesser tendancy to fade. The tough dogs will be fine for slow speed wheeling but may have a tendancy to fade with high speed rough tracks.
Hope this helps
Dan

Hobzee wrote:Funny how comp guys choose the 4Way adjustables. I wouldn't run Hydraulic in a comp rig - Foam Cell for me all the way.

Do you mean 4way as in Tough Dog? Because they are foam cell technology.

Oh, and my first choice for a Disco would be Bilsteins mate.

Bilstein are easily the preferred shock amongst Landy enthusiasts.

Foam cell shocks like the tough dog and the rancho most definately do overheat and fade off. The tough dogs seem to be resistant to this which I assume is due to their bigger capacity and I don't think they have the triple shelling of the rancho. The problem is though, if/when they do fade they don't ever properly come back again when they cool off as the material inside degrades. If you tour offroad with these shocks then I would recommend that you don't run foam cell shocks. If there is no touring then they'll probably be fine. You cant run these upside down if you're trying to fit Landcruiser etc shocks.

For gas shocks there are different designs. There is what commonly called twin shell or gas like the normal OME, Koni, Monroe, TJM etc etc etc. These use a low level of gas pressure to help prevent the airation and fade off of the shock. These come back ee after fading and they also can t be run upside down.

There is also the monotube type shocks like the Bilstein, LTR and any other remote canister shock. In this setup the oil is physically seperated from high pressure gas and the shock can not airate or fade. I have heard as much as they stiffen when hot, but my experiences with these are that they continue to work perfectly and maintain handling and control when other shocks have long given up. The LTR has a double shell which give protection, the Bilstein has a single shell which is thick and will remain undamaged after many twin shells are badly damaged, but if they do get dinged... then throw them out - it's not a common problem even in 4WD's though. I'd definately run these if touring, and also if you're fitting shocks into your truck upsidedown.

For shock rates... it has a lot more to do with the valving of the shock than the method used to control fade and control volume as the shaft travels. well... then they get hot and things change a bit.

The shock length is what will make changes with articulation if anything. Gas pressure makes no real difference.

I believe that the longevity of the shocks has a lot more to do with the build quality, the quality of every single part, the tolerances and the design.

As with everything in life there is a lot more to them then meets the eye and a lot that can go wrong and compromises made.

The theory that the foam cell shocks are better is good advertising. Time will tell if someone gets it right.

Bilsteins are more responsive but if you ding the outside of the shock say good night. Mind you the Tough Dogs don't like too much side loading either.

It has been a while since I have pulled at a Bilstein shock but if I remember correctly it came out very slowly as do Dobinsons.

Can someone correct me on that point.

Shane

I'd actually steer clear of Dobinsons.

Now I might upset some people, and I'm sure plenty of people are happy with them, but I worked for Dobinsons in their spring factory here in Rockhampton about 2 years ago.
As far as the springs go, both coil and leaf, I'd have to say top stuff! The machining and equipment they use to make them is top of the line and as far as testing and quality goes, brilliant.
BUT! The shocks are just that! Shocking! We would get pallets and pallets of the things in, and they would source them from the cheapest Malaysian/Chinese/African (maybe even New Zealand...kidding!) and we'd have to go through and test each one by hand, moving them up and down to see if there was any play, and honestly, at least 60% were able to be moved with no resistance at all!
They were actually that cheaply bought that they made a profit on the useless ones selling them to a local scrap metal yard!.
The good ones got painted, a sticker and boxed to look all nice and neat, but the bins full of dodgy shocks had much more than the shelves.
Even the owners (2 brothers) told me never to buy the shocks!

Operations may have changed since then, as I said it was a couple of years ago, so they may have actually changed to a decent supplier, I really don't know. But I know I wouldn't be taking any risks.

And to add to the "think very carefully before buying" category - don't buy Pedders IMO.

Did a ToughDog and as the Bilsteins were a few weeks away bought a pair of foam cell Pedders as a stop gap and they didn't even last a single day trip.

One had no damping at all and the other was leaking around the shaft seal

4WD Stuff wrote: It has been a while since I have pulled at a Bilstein shock but if I remember correctly it came out very slowly as do Dobinsons.

Can someone correct me on that point.

Shane

Shane they come out pretty quickly, they can be a mongrel to compress again when you need to!

Hobzee wrote:You wont notice that effect (gas pushing down) but nice theory. The rebound from the springs is much faster than the gas cares to expand and the coil will still be pushing out against the shock.

Gas are a bit stiffer than oil/hydraulic and so you get a slightly sportier stiffer ride. Landrover/Rangie guys like the soft oil shocks. Toyota and Nissan guys tend to go the sportier gas shocks.

Foam Cell are stiffer again. They dont get as hot and when they do warm up they dont fade (go soft) like Hydraulic and gas do. Comp guys should run Foam Cell unless they have the multi valved or coil overs. I believe all adjustable shocks are hydraulic ... bottom the range in technology terms. Funny how comp guys choose the 4Way adjustables. I wouldn't run Hydraulic in a comp rig - Foam Cell for me all the way. Remote canister shocks are a step towards keeping gas shocks 4cool, but that's all they achieve.

well for starters foam cell heats up WAY more than nitrogen gas. this is why 4 way make such big piston and bore diameters to try and dissipate that heat. foam cell was originally designed for use in steering stabilisers so when laid on its side would not suffer from aeration. along the way someone thought it would be a good idea to make a shocker from it.4 way and rancho are the same. once foam cells heat up they will break down the cell, and this damage is permanent.nitrogen gas shocks will usually cool down and restore. foam cell is cheap to manufacture and assemble, top quality gas is niether of these which is why they can be more expensive. look at kyb which is one of the worlds experts on shockers and they are the only ones to make a dial adjustable full nitrogen shock.

Mr Sausage wrote:I'd actually steer clear of Dobinsons.

Now I might upset some people, and I'm sure plenty of people are happy with them, but I worked for Dobinsons in their spring factory here in Rockhampton about 2 years ago.
As far as the springs go, both coil and leaf, I'd have to say top stuff! The machining and equipment they use to make them is top of the line and as far as testing and quality goes, brilliant.
BUT! The shocks are just that! Shocking! We would get pallets and pallets of the things in, and they would source them from the cheapest Malaysian/Chinese/African (maybe even New Zealand...kidding!) and we'd have to go through and test each one by hand, moving them up and down to see if there was any play, and honestly, at least 60% were able to be moved with no resistance at all!
They were actually that cheaply bought that they made a profit on the useless ones selling them to a local scrap metal yard!.
The good ones got painted, a sticker and boxed to look all nice and neat, but the bins full of dodgy shocks had much more than the shelves.
Even the owners (2 brothers) told me never to buy the shocks!

Operations may have changed since then, as I said it was a couple of years ago, so they may have actually changed to a decent supplier, I really don't know. But I know I wouldn't be taking any risks.

Dam don't hold back hey.

I hope you did a good job of separating the good from the bad. It sounds like they were feeling their way through trying different factories. They tell me that they now use the Viton seals, the same seals as Bilstein use.

The Dobinsons shocks are valved a bit too firm for most people, they must have been designed by someone who drives a sports car. Some people love them. Generally I recommend Lovells shocks and Dobinsons coils.

But wow, you have really let the cat out of the bag.

Shane

Mr Sausage wrote:I'd actually steer clear of Dobinsons.

Now I might upset some people, and I'm sure plenty of people are happy with them, but I worked for Dobinsons in their spring factory here in Rockhampton about 2 years ago.
As far as the springs go, both coil and leaf, I'd have to say top stuff! The machining and equipment they use to make them is top of the line and as far as testing and quality goes, brilliant.
BUT! The shocks are just that! Shocking! We would get pallets and pallets of the things in, and they would source them from the cheapest Malaysian/Chinese/African (maybe even New Zealand...kidding!) and we'd have to go through and test each one by hand, moving them up and down to see if there was any play, and honestly, at least 60% were able to be moved with no resistance at all!
They were actually that cheaply bought that they made a profit on the useless ones selling them to a local scrap metal yard!.
The good ones got painted, a sticker and boxed to look all nice and neat, but the bins full of dodgy shocks had much more than the shelves.
Even the owners (2 brothers) told me never to buy the shocks!

Operations may have changed since then, as I said it was a couple of years ago, so they may have actually changed to a decent supplier, I really don't know. But I know I wouldn't be taking any risks.

I am sure that some will be interested in the follow up I did.
I phoned Dobinsons for their view on the above. About 5-6 years ago they did get some Gabrial shocks made up from America as did other Australian companies. As it turned out a lot of them were binned therefore another supplier was sourced. So what Mr Suasage says is true but further back then a couple of years. Now, Dobinsons have probably got the lowest return rate along side Lovells shocks.

Cheers
Shane

cheers for all that guys, should have know better than to think it would be simple, but a big help anyway. Tell me though, my truck is purely for off road weekend use, nothing else other than getting there, and am having silly thoughts of venturing down the comp truck direction in an evolution type manner. When am out there, am working everything pretty hard, (and my in-experience means plenty silly lines working things harder than they need), but not necessarily fast just hard and so there for would assume am getting the shocks quite warm and so thinking should be running the Bilsteins rather than the Tuff Dog?

What sort of style comp? If you're talking slow speed rock crawling, your shocks won't be getting as warm as high speed racing over corrugated roads where the shocks are working overtime.

mmhey wrote:

Hobzee wrote:You wont notice that effect (gas pushing down) but nice theory. The rebound from the springs is much faster than the gas cares to expand and the coil will still be pushing out against the shock.

Gas are a bit stiffer than oil/hydraulic and so you get a slightly sportier stiffer ride. Landrover/Rangie guys like the soft oil shocks. Toyota and Nissan guys tend to go the sportier gas shocks.

Foam Cell are stiffer again. They dont get as hot and when they do warm up they dont fade (go soft) like Hydraulic and gas do. Comp guys should run Foam Cell unless they have the multi valved or coil overs. I believe all adjustable shocks are hydraulic ... bottom the range in technology terms. Funny how comp guys choose the 4Way adjustables. I wouldn't run Hydraulic in a comp rig - Foam Cell for me all the way. Remote canister shocks are a step towards keeping gas shocks 4cool, but that's all they achieve.

well for starters foam cell heats up WAY more than nitrogen gas. this is why 4 way make such big piston and bore diameters to try and dissipate that heat. foam cell was originally designed for use in steering stabilisers so when laid on its side would not suffer from aeration. along the way someone thought it would be a good idea to make a shocker from it.4 way and rancho are the same. once foam cells heat up they will break down the cell, and this damage is permanent.nitrogen gas shocks will usually cool down and restore. foam cell is cheap to manufacture and assemble, top quality gas is niether of these which is why they can be more expensive. look at kyb which is one of the worlds experts on shockers and they are the only ones to make a dial adjustable full nitrogen shock.

Hi, I am not disputing you but how do you know this stuff, is it 2nd hand info or just experience.

Cheers
Shane

interesting thread.....

Another one for your mix.

Koni are one of the best out there, and are not pressurised. Plenty of race cars running on them. I know all about heating, but somehow Koni manages. They just seem to ride so well.

We used to run Bilstein in the rally car, never faded them. Monotube can be dented, but it would take one hell of a knock.

Paul