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Heavy Duty Foam Cell Shock Absorbers
(Specially formulated for Heavy Duty and coil sprung 4WDs' usage for the
elimination of vehicle's body roll, bounce and dive)


The use of Micro-cellular foam inserts has produced a new breed of shocks, which are more resistant to fade. After heavy work, all shock absorbers, whether they are hydraulic, gas or foam cell shocks, show signs of fade or lack of damping force. However, Foam Cell shock absorbers are far more resistant to fade than other types of shocks. Tests have shown that foam cell shocks maintain almost optimum efficiency in conditions that can cause gas and especially hydraulic shocks to lose much of their dampening force.

To understand how foam cell shock absorbers could produce such superior performance, we will look at the common causes of fade and how foam cell inserts affect shock absorber operation.

AERATION is the mixing of the oil with gas or air in the oil reservoir, i.e. the outside cylinder of the shock. This causes the oil to "FROTH", reducing its viscosity so that it passes more freely through the valving. This causes the shock to lose some of its damping force and the air bubbles passing through the valving causes the shock to operate unevenly and noisily.

Also, when aerated, the oil is compressible. Instead of the oil being forced through the valving and into the outer cylinder, the action of the shock absorber compresses the oil within the pressure cylinder. When extremely aerated, a shock provides a cushioning effect rather than a controlled resistance to movement. This is loosely called "FADE".

CAVITATION occurs when the oil inside the pressure chamber starts to boil. This is due more to LOW pressure than to high temperature, although both contribute to cavitation.

The pressure drop is caused when the shock extends Rapidly, but the flow of oil into the pressure chamber is insufficient to fill the space left by the retreating piston and rod. A vacuum is created in the pressure cylinder and the oil begins to boil. Under low pressure, a liquid can in fact boil without heating, and this is what occurs when a vacuum is created inside a shock absorber- instantaneous boiling due to a sudden drop in pressure. The boiling of the oil produces air bubbles within the shock, which produces the same effects as aeration of the oil.

Gas pressurization of shock absorbers can significantly improve their performance, however gas shocks are also subject to aeration & cavitation. Under unrelenting and extremely rough conditions a gas shock provides only marginally resistance to fade than a standard hydraulic unit. The FOAM CELL shock absorber, on the other hand, performs with an almost negligible reduction in dampening force. To do this, it must virtually eliminate aeration & cavitation. How does it do this?. Quite simply. The foam cell insert occupies the space in the oil reservoir which in the case of hydraulic or gas shock absorbers would contain air or gas. While oil can mix with air and even pressurized nitrogen, it cannot mix with the foam. The foam used in shocks has tiny closed cells, which contain bubbles of gas. The oil inside the shock cannot mix with the gas bubbles inside the foam because they are enclosed inside the foam.

When the shock is compressed, the foam works not like a sponge absorbing the oil, but rather like a spring or air bag. At the end of the compression stroke, the compressed gas bubbles inside the foam push the oil back into the pressure cylinder.

No oil / air or oil / gas mixture has occurred, so there is no risk of aeration. The pressure extended by the foam pressing the oil back into the pressure cylinder prevents cavitation occurring. Hence, no aeration and minimal cavitation for unrivalled resistance to fade.



Extraordinary features :

  • Rod Wiper Seal

  • Multi Lip Seal

  • Massive 18mm Rod

  • Hardened Sintered Piston Rod

  • Double Chrome Plated Rod

  • High Temperature Resistant Fluid with Twin Tube Design

  • Massive 41mm Bore

  • Custom made for each 4WD

  • Valved tuned to match OEM or Tough Dog Spring rate

  • OEM or Longer Length Shocks to suite Standard or Raised 4WD for maximum articulation, comfort, safety & durability

  • 2 year / 40,000km Warranty (Refer Important Notice & Conditions on Warranty).


Both the Heavy Duty Foam cell and Gas Charged shock absorbers come with multi stages velocity sensitive valving and large piston for better control and damping, larger twin tube design for more fluid retention and longer piston travel, multi-viscosity synthetic oil for better heat resistant and the high quality heat and wear resistant piston and shaft wiper seals for longer life which are all lacking in the cheap original shock absorbers and even in some of the aftermarket shock absorbers.

Further more, most of the Tough Dog shock absorbers come with 2 or sometime 3 different lengths for different raised height applications (i.e. the original length to suit the original springs height and the longer lengths to suit the raised height of Tough Dog springs) because when a vehicle is raised by higher rate springs, it would certainly need to replace the original length shock absorbers with a set of longer length (which is equivalent to the amount of height raised)  shock absorbers as otherwise, the travel of the shock piston rod would not be sufficient to give a good and stable ride on the road and good wheels' articulation when off-roading. A shock absorber cannot be too short or too long than necessary. A too short a shock absorber would cause the piston to hit against the top of the shock absorber when the vehicle body is bounced up by its springs or doing a sharp cornering or braking. A too long a shock absorber would cause the piston to hit against the bottom of the shock absorber during its downward stroke or doing a sharp cornering or braking. Too long or too short a shock absorber would not only constitute to an un-comfortable and un-safe ride it would also damage the shock absorber itself in a very short period of time. Tough Dog shock absorbers are the only one that have come up with the different lengths and the different type of shock absorbers to suit the different leaf sprung and coil sprung 4wds, the different applications and the different vehicle's raised height as Tough Dog does not believe in giving its customers a compromised suspension system !  Tough Dog shock absorbers are also valve coded to match each vehicle's weight, weight distribution and the rate of the original springs or Tough Dog springs.



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