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Shock Absorber Information

We sell approximately 20 different brands of shock absorbers for Cars, Utility vehicles, 4 wheel drives, Light trucks, Trailers, Caravans and Motorcycles!

We only sell reliable products that are competitively priced, are backed by their respective manufacturers and have fair and decent warranties.

We have discovered that over the years of being in the forefront of the suspension industry, some brands are not too well suited to certain vehicle models or vehicle uses despite what some of the brands may have you believe!

Before you buy any shock absorber, ask us first!

Below are some of the brands we currently sell however not all are listed:

BILSTEINKONIEFSMONROEOLDMAN EMU POWERDOWN, RAW, KYB, LOVELLS, DOBINSONS, TOUGHDOG, FOX, ULTIMAXYZ, BOGESACHSOZTECSPAX

Motorcycle Shock Absorbers

We now sell IKON motorcycle shock absorbers and front fork replacement springs.

BIKE   ikon  ikie  ikon family


 

What are shock absorbers?

Essentially, shock absorbers do two things. Apart from controlling the movement of springs and suspension, shock absorbers also keep your tyres in contact with the ground at all times. At rest or in motion, the bottom surface of your vehicles tyres are the only part in contact with the road. Should at any time a tyre’s contact with the ground is broken or reduced, your ability to drive, steer and brake is severely compromised.

Despite some popular belief, shock absorbers do not support the weight of a vehicle, its the springs that do the work.

 

How do they work?

Firstly, a little bit of science. Shock absorbers work by taking the kinetic energy (movement) of your suspension and converting it to thermal energy (heat) that is then dissipated into the atmosphere through the mechanism of heat exchange.

But it’s nowhere near as complicated as it may sound.

As mentioned, shock absorbers are basically oil pumps. A piston is attached to the end of a piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through orifices (tiny holes) inside the piston. Because the orifices only allow a small amount of fluid through the piston, the piston is slowed which in turn slows down spring and suspension movement.

Shock absorbers automatically adjust to road conditions because the faster the suspension moves, the more resistance they provide.

 

Types of shock absorbers

Although all shock absorbers do the same job, different types of vehicles and suspension designs require different types of shock absorbers which can appear radically different.

No matter the application, all shock absorbers fit into one of three broadly defined types – conventional telescopic shock absorbers, struts or spring seat shocks.

Conventional telescopic shock absorbers

This is the simplest type of shock absorber and is generally replaced rather than repaired. This type of shock absorber can be found on both front and rear suspension systems and is relatively inexpensive.

Strut type shock absorbers

Although they do the same basic job, struts replace part of the suspension system and must be more ruggedly built to cope with greater loads and forces. Although most commonly seen on the front and rear of small to medium cars, larger cars and utes are now tending towards strut based suspension design. The strut category is further divided into sealed and repairable units. As the name suggests, sealed units are designed to be fully replaced, whilst repairable (McPherson) struts are able to be fitted with replacement strut cartridges.

Spring seat shocks

The spring seat type shows characteristics of both telescopic and strut type shock absorbers. Like struts, a spring seat shock is a suspension unit and damping device in a single unit. Unlike struts however, they are not designed to be subject to high side loads. Built using similar components to conventional shock absorbers, spring seat shocks are also sealed requiring full replacement. They are commonly now found in vehicles such as Toyota Hilux, Landcruiser Prado, Nissan Navara etc.

We sell over 20 different brands of shock absorbers!

Why? Because we can and we do! This gives you our customer more choice!

Manufacturers supplied and fitted shocks require replacing around 60,000 to 80,000 kilometres from new. Why? All new cars, 4×4’s, utility vehicles and commercial vehicles have soft springs and coils. Soft small bore shock absorbers and are all mounted on soft rubber components. WHY? So the manufacturers through their dealers are able to sell new vehicles that drive smoothly and softly. The result in the real world is that when we start using them, to and from the shops, fitting permanently bolted on accessories we inadvertently overload them and also drive them hard often on harsh terrain.  Cooking those sweet little new shocks and playing a crushing game on the springs!

For shock absorbers please read on. Please read our springs section for additional information. Thank you

Many of us sheepishly avoid eye contact when the subject of shock absorbers comes up. It seems that everyone we speak to is an authority on the subject, often with strong views on the best shockers for our vehicles be it a sedan, ute or 4×4 vehicle.

This page is an attempt to explain in simple terms what a shock absorber is, what it does and the different types available. Hopefully it’ll arm us with some self respect to at least maintain eye contact with the experts.

What’s a shock absorber?

It’s a device that offers resistance when the suspension moves up and down. The neat thing about shock absorbers is that they only offer resistance when there is movement and the amount of resistance is related to the speed at which the suspension moves. Typically, the faster the movement, the higher the resistance.

Why do we need shock absorbers?

Our cruisers use springs to keep the vehicle up. Just like any spring, if we compress or stretch it and then let go, it will keep bouncing up and down for a long time.

Rough Ground Example

If we follow the movement of the vehicle (magenta curve) after hitting a bump, without shock absorbers, the vehicle would continue to bounce up and down well after hitting the bump. Shock absorbers offer resistance to this uncontrolled movement so that the vehicle quickly returns back to a level ride on level ground.

In the case above, by offering resistance to (or more correctly damping) the movement, it takes energy away and dissipates it as heat (that’s why shock absorbers get hot).

How does a shock absorber work?

Most shock absorbers for our Cruisers are based on a piston pushing (as the suspension compresses – compression) and pulling (as the suspension extends – rebound) inside a cylinder containing hydraulic fluid.

The piston contains holes, slots, valves, shims etc which controls the amount of fluid which can pass through it. A basic interpretation shown to the left displays 4 large holes in the piston. As the piston moves in the cylinder, fluid is forced through the holes to the other side of the piston and whilst doing so, creates a resistance to the movement. The amount of resistance is often referred to as the damping rate.

Inside Shock

There’s a lot more in there of course. There are more valves, etc at the base, gas chambers etc which we won’t go into right now.

As you may have guessed, by altering the size and number of holes, you can alter the amount of restriction to flow and hence the amount of damping force the shock absorber exerts. We alter the damping rate.

Shock Under Pressure

In the above example, with 2 smaller holes instead of the previous 4 large holes, the damping rate will be much higher. Where things become clever here is the amount of restriction can vary with speed with which the piston moves inside the cylinder. You may have come across the term “multi stage valving” used to describe a shock absorber, or advertising claims of “5 stage valving”. This describes the fact that there are a number of distinct stages in the amount of restriction to flow within the shock absorber.

Another important aspect of damper performance is the thickness (or viscosity) of the hydraulic fluid we use. The thicker it is, the higher the damping rate. Conversely, the thinner the oil, the lighter the damping. This is important to remember as we learn about shock absorber fade.

So why do we need different damping rates?

The general design requirements of shock absorbers for our Cruisers is to have “light damping” or minimal restriction for slow speed movement (to keep things comfortable and to enable the wheels to track over small undulations). For high speed piston movement, we’d be looking for high damping or high restriction to keep the suspension from bottoming out or extending back too quickly.

Yes, you did read it correctly. The bit about extending back. You see a shock absorber works both ways and interestingly, the amount of restriction or damping rate as the suspension compresses (damper compression rate) is different to that as the suspension rises back (damper rebound rate).

This of course is a very simple way of looking at it and shock absorber design is a real science which we’re almost insulting by telling it in such a simple way…. But it is Shock Absorbers for Dummies after all.

What’s all this stuff about fade?

 A shock absorber’s worst enemy is heat. High heat can alter the viscosity of the hydraulic oil and it becomes thinner. If we remember, the thinner the oil, the smaller the resistance and hence a lowering of the damping rate. The car feels loose in the suspension and tends to bounce around much more, with higher chances of bottoming out.

Another problem with some designs can be aeration. There’s gas or air inside the shock absorber as well as oil. The gas or air may mix with the hydraulic oil which again offers less resistance and lowers the damping rate. It’s a bit like shaking up a Coke bottle. Looks like liquid until you release the top and all the gas comes bubbling out of the liquid. As we’ll soon see, there are a number of designs which address the problem.

People keep talking about different types of shock absorbers. What do they mean?

Ah, we’re into the 4×4 magazines and online chatroom’s territory here. Ever been talking to someone claiming to be an expert and he (or she) throws you a line like “They’re foam cell shockers mate, ya can’t go wrong”. Naturally you agree and subsequently avoid any further eye contact.

Let’s see if we can explain some of it.

 

Twin Tube GasThis type of shock absorber has two tubes. An outer reservoir tube and inner pressure tube. The piston moves up and down inside the pressure tube and oil is forced through the compression valve or the rebound valve.As the oil displaces, an inert gas such as nitrogen at relatively low pressure (around 5 atmospheres) is maintained on the oil in the reservoir tube.The reason why an inert gas at pressure is used, is to reduce the chances of aeration. This type of shock absorber eventually will fade if used hard and simply requires time to cool for full damping to return. Twin Tube Shock Absorber
Foam CellAgain a twin tube but an interesting design where instead of allowing any gas to come in contact with the hydraulic oil, nitrogen impregnated foam cells are used.These shock absorbers virtually eliminate aeration and will generally hang on a bit longer than the twin tube gas shock absorbers before fading. Unfortunately if this type of shock absorber is overheated, it will not regain its damping qualities when cooled. Foam Cell Shock Absorber

 

 

Mono TubeAs the name implies, this type of shock absorber uses only one tube and the piston valving controls both rebound and compression damping. A floating piston separates the nitrogen gas from the oil and the gas is at a high pressure generally above 20 atmospheres.This type of shock absorber is more prone to stone damage than the twin tube types. Once the tube is hit, the rod piston and/or floating piston will no longer seal properly against the cylinder wall.With the gas at the bottom of the shock absorber, it’s difficult to design one with as much travel as the twin tube designs above. As such it’s a popular shock absorber on road cars and as it heats up, the gas pressure increases and exerts more force on the oil. The end result is that the damping rates increase with heat. Mono Tube Shock Absorber

 

 

Twin Tube HydraulicThis type of shock absorber is similar to the twin tube gas type except instead of using an inert gas at pressure, it simply uses air at atmospheric pressure.Generally, it’s prone to aeration and will fade quickly. Allowing the shock absorber to cool will see a return of its damping qualities. Hydraulic Shock Absorber

 

For more information please contact us.

icon (08) 9302 6648      iconemail apesprings@bigpond.com

Thank you we hope you have found this article of interest.