Foam Cell vs Monotube Shocks: Which is Best for Corrugations?

Think for a moment: you have been able to get some time away from work, loaded the 4WD right up to the gunnels, and are now heading into the bush beyond the black stump.

Everything seems to be going great until you come across something that will make you wish that you had stayed at home. That is right, washboard corrugations that seem to go on forever and can shake you right down to the bone in your trusty 4WD. 

The corrugations are the ultimate test of any four-wheel drive. Once you begin researching about upgrades that could make your suspension suitable for handling those terrible trails of dirt, you tend to face two distinct technologies head-on.

You will inevitably get involved in that large debate about foam cell vs monotube shocks. Each technology has its own die-hard fans. They both believe that they are the best thing after sliced bread when it comes to off-road touring.

However, when you are many kilometres away from any mechanic while driving through a road that is rougher than a giant cheese grater, marketing is absolutely meaningless.

All you need at that point is something that works and keeps those tyres stuck on that dirt without overheating and turning you into a bouncing pogo stick. Let us dive deep into how each of these two giants performs on those horrible trails.

How do Corrugations Destroy Normal Suspension?

It is only when we analyse exactly how corrugation affects your vehicle that we can begin to appreciate what we are discussing here. As you roll through corrugations at full throttle, your shocks are constantly extending and contracting with violent force, as much as 12 times per second. Each one of those movements creates friction, which creates heat, which is an enemy to the shock absorber.

A factory shock absorber, when subjected to such heat, will eventually have its oil boil and mix with gas, producing a foamy and aerated substance. This phenomenon is referred to as cavitation, which renders the shock incapable of absorbing any more bumps. 

This produces an extremely dangerous situation known as shock fade, where your huge touring vehicle behaves like a ship in a storm, bouncing wildly and losing all traction. For any shock absorber to conquer corrugations, it must first accomplish one task (dissipate heat) effectively.

What Is the Mechanism of Monotube Technology?

Now let us take a look at our first competitor. The monotube shock is precisely how it looks: a large single cylinder. On the inside of that cylinder, the oil and the high-pressure nitrogen gas are separated entirely from each other with an inner piston that can float freely. 

The single outer wall means that the inner wall could be massive. Hence, more surface area means the shock will react extremely quickly to changes in conditions.

When discussing the performance of monotube shocks, corrugations come into play. 

Since the oil in the monotube sits right next to the outer steel shell of the shock itself, any change in temperature is immediately conducted straight to the outside air. This causes extremely efficient cooling of the shock as the air flowing underneath your vehicle hits it, and high-pressure gas inside the monotube actually prevents cavitation and boiling of the oil itself. 

If you need a shock absorber that will react instantly to all the irregularities of the road while keeping your tyres firmly glued to the ground for maximum stability, the monotube is a godsend. They usually have a sportier feeling compared to other types of shocks.

How Do the Foam Cell Shocks Work?

Now, we turn the coin over and consider the other side. Foam cell shocks work with a double tube principle. So, they have an inner tube where the piston travels and an outer tube serving as a reservoir. 

Usually, the shocks and struts working on the double-tube basis contain the gas-air mixture in their reservoirs. This combination would be disastrous for your shocks when driving through bumpy country roads. 

However, with foam cells, this gas-air mixture is substituted with a special sleeve of the closed-cell foam. Just picture it as a very dense sponge, but it consists entirely of nitrogen bubbles.

Such a small change is completely innovative as far as off-road driving is concerned. Indeed, the fact is that with gas safely contained within the closed cell, there is simply no way for it to contaminate the oil in the shock. 

In addition, you do not require the airspace anymore. Therefore, you can fill the outer chamber to its absolute capacity with oil, and the amount of oil in your shock will be enormous. Of course, such a large quantity of oil gives more thermal mass, and it takes a great deal of time to warm it up.

Nitro Gas vs Foam Cell: Which is better?

But before we begin the battle between the two titans, we need to explore the cheap option that most customers end up purchasing. Upon examining the factory replacement options available in the market, you will realise that it often comes down to choosing between a nitro gas vs foam cell setup. 

A nitro gas shock uses a conventional twin-tube system that does not include the innovative foam technology. Low-pressure nitrogen is used to help minimise the chance of oil aeration. These shocks work perfectly well for city driving and casual weekend camping in the smooth dirt tracks.

However, if you plan on using these shocks on routes such as the Gibb River Road or Cape York, then you are going to be in for trouble. The violent bumps encountered on these rough surfaces are bound to exceed the capacity of the low-gas-pressure shocks, resulting in foaming of the oil. 

This will lead to your car bouncing around wildly. The best thing about upgrading to foam cell shocks is that it solves the problem of oil aeration in the shocks. It becomes the bare minimum requirement for remote travel over long distances.

Foam Cell vs Monotube Shocks: The Differences

Standing inside the workshop weighing your options when you evaluate whether to choose foam cell vs monotube shocks, one thing matters most: the terrain, your actual driving style, and the feel of your car. 

Monotubes are true kings of performance. They deliver very stiff yet precise and controllable handling. These are perfect for light cars or fast dirt driving where precision in control is essential. 

Monotubes have the highest cooling capacity due to their one-wall design. Nevertheless, all that stiff control is accompanied by a small downside. These are a bit stiffer on low speeds. 

In case you encounter any bumps such as sudden ledges or sharp-edged holes in the road, you will definitely feel every single impact in your seat. High-pressure gas tends to always push outward. Hence, the initial contact becomes harsh.

Foam cell shocks, however, reign supreme when it comes to comfort over endless miles of corrugations. Since they do not have the high pressure of gas continuously acting upon the piston, they deliver a much more cushioned, softer ride over the quick bumps. 

The shock absorbs the harshness and keeps your back and dashboard safe. Although they do not cool down as quickly as the monotube shocks, their huge capacity for oil ensures that they will not get hot so quickly. In the end, they are a very hard act to beat when it comes to prolonged outback touring.

Why Is Factoring Weight for Touring Load Planning Important?

Suspension is always going to be a factor to take into account when it comes to the addition of all sorts of accessories to the touring vehicle. Touring load planning is as important as having the proper shocks installed on a car. 

What is the weight of all the accessories that come in a typical touring vehicle? Well, let us break it down into numbers: a heavy-duty steel bull bar, a winch, dual battery packs, steel side steps, a roof rack, a rooftop tent, rear drawers filled with tools, storage, and a full fridge.

The weight added to the car will amount to hundreds and hundreds of kilograms.

The addition of all the above accessories will change drastically how the vehicle will behave under normal conditions. 

Monotube shocks feature high pressure of the internal nitrogen gas. This means they serve as additional springs for the suspension that can absorb the additional weight and prevent waddling. 

However, if you want to reach the legal load capacity, then those large foam cell shocks are what you need. The size of their components and oil amount will allow damping of the kinetic energy generated by the massive three-tonne vehicle.

How to Select the Best Market Shock Absorber Options?

Once you begin looking into the different shock absorber options available on the market, you will soon realise that there is a tremendous difference in the price as well as the physical size of the parts. Consult a professional’s expertise to get the best 4×4 suspension upgrades. 

Monotubes are very precise parts engineered for perfection. It takes exact tolerances to make the piston float within the part, and it is often costlier to manufacture and repair than other models.

Foam cells depend on brute strength and sheer size to work properly. Because of the twin-tube structure, the outside housing can become damaged by a flying rock while driving down a dirt road, but the shock will continue to operate flawlessly, as the pistons inside run within another tube. 

The moment a rock becomes lodged inside a monotube, the shock will be destroyed due to the piston being blocked. This simple fact makes the foam cell a preferred choice among those who enjoy bashing through rocks and dense undergrowth. You give up a bit of precise steering in return for unmatched longevity and comfort.

Frequently Asked Questions

Are monotube shocks too stiff for daily driving around town?

They can certainly feel firmer than factory suspension, especially when the vehicle is completely empty. Because they are pressurised to prevent oil aeration, that pressure translates into a tighter, stiffer feel over speed bumps and potholes in the city. If you prefer a completely plush, soft ride for your daily commute to work, you might find a heavy-duty monotube setup a bit too rigid for your liking.

Can foam cell shocks handle high-speed off-roading like sand dunes?

They absolutely can handle sand and high-speed tracks, but they react differently than a monotube. Because they do not have that high-pressure gas forcing the shock to rebound instantly, they can feel slightly slower to react to massive, sudden changes in terrain like deep whoops on a sandy track. They will not fade or boil, but they might feel slightly less sporty or snappy when you are throwing the vehicle around quickly.

Do I need a lift kit to upgrade my shock absorbers?

Not necessarily. You can absolutely buy upgraded heavy-duty shock absorbers that are designed specifically to bolt straight into your vehicle at the standard factory height. However, most people who are tackling brutal outback roads usually upgrade their coil or leaf springs at the exact same time to carry their touring weight better, which naturally results in a slight suspension lift.

How long do these heavy-duty shocks actually last on the road?

Their lifespan completely depends on how hard you treat them. If you spend your weekends pounding over brutal corrugations at high speeds while carrying three tonnes of gear, you will wear out any shock much faster than someone driving on the highway. Generally speaking, a high-quality aftermarket shock from a reputable brand will easily outlast your factory suspension, often providing tens of thousands of kilometres of reliable off-road performance before needing replacement or rebuilding.

Time to Upgrade Your Ride: Get in Touch Today

Deciding between whether foam cell vs monotube shocks will be better for your vehicle is probably the most important decision that you will have to make. Depending on what you are looking for, whether it is the ultra-fast handling and rapid heat dissipation provided by the monotubes or the huge capacity for oil, plush ride, and robustness offered by foam cells, you should get the equipment that you can rely on. 

There are no second chances when it comes to the outback, and you cannot afford to skimp on your shock absorbers if you do not want to end up stuck along the sides of a muddy race track. Drop into Sharp 4×4 Australia today, and let us help you build a suspension package that will eat up the worst corrugations this country has to offer.