Control

Independent suspension systems for

camper trailers – what are the main

differences and how can you choose

the one that will suit your needs?

WORDS BY SCOTT BUTLER, PHOTOGRAPHY BY BRETT SHEARER

The UlTImaTe

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TeChNICalIndependent Suspension

When purchasing a new camper trailer, you will notice that nearly every manufacturer has their personal ideas on suspension

set-ups. These ideas are likely to be influenced by their personal experiences as well as cost of parts and installation. With the camper trailer market being so competitive, you can afford to weigh up the options that are available and insist on the right set-up for your needs.

It is always a good idea to quiz the manufac-turer on the type of suspension set-up that they have under their camper trailer and ask why it would be the one for you. However, before you can ask the right questions, you will need to know some of the different styles available, this way you will be able to weed out the truth from a sales pitch.

In the past, independent suspension set-ups were slow to take off in the camper trailer mar-ket, but over time they have grown to become one of the most sought after upgrades. There are many different versions of suspension set-ups – from the older style of leaf springs with a

solid axle to the new independent suspension found on nearly every upmarket and even on a couple of lower-spec’d camper trailers. These new styles of suspension set-ups can be a little confusing, so we decided to bring you the facts about how they work and what are some of the pros and cons to look out for. The draw for manufactures to move over to an independent suspension system is the ability of keeping the tyres of your camper trailer in contact with the ground as much as possible; this is much more achievable when both wheels work indepen-dently of each other.

There are four main styles of independent suspensions available: independent coil, inde-pendent air, independent leaf and independent asymmetric link (MC2) suspensions. When choosing a camper trailer, you will rarely have a choice of suspension style, but if you are choosing between two different campers, the style of sus-pension may help you make up your mind which one will suit your personal needs and budget. So let’s get into it, so you can know which suspen-sion package will best suit your needs.

Independent control arms awaiting installation

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INDEPENDENT COILIndependent coil suspension for trailers is commonly thought to be one of the best and most affordable suspension set-ups out of all the independent styles. Compared to a leaf sprung set-up, they are renowned to be more reliable with less chance of spring fatigue. In saying this it doesn’t mean that it is unsus-ceptible to damage or wear and tear, but compared to the cheaper leaf sprung suspen-sions of yester year a coil spring will have less breakages than a leaf spring.

An independent coil spring suspension set-up has three main parts being, trailing arms, coils and shock absorbers. The trailing arms have a pivot point at the leading edge of the arm, normally in an “A” shape with a coil situated between the chaise and trailing arm, and a shock absorber mounted at the rear to control the up and down movement. It is com-mon to see a limiting strap added to reduce any chance of the shock being destroyed due to excessive extension on the shock absorber.

This system allows both wheels to travel independently of each other, with the ride

comfort of a coil spring. A big advantage in us-ing a coil over a leaf spring is the reduction in weight. A set of leaf springs that would be able to hold a 1600kg camper trailer would weigh around 18kg, whereas coils that hold the same weight would only weigh 4kg.

Having a reduction in your camper’s unsprung weight is vital when towing, as this will increase the suspensions ability to keep the tyres in contact with the ground as well as reducing the overall weight of the trailer giving you more carrying capacity (GVM). It is now commonplace to use coils in many late model vehicles, so it understandable that camper trailers are following the same line in suspen-sion set-ups.

This suspension works well with all weighted camper trailers from 450kg to 1700kg. Things to look out for when purchas-ing a camper with a coil sprung independent suspension are bump stops and limiting straps that will stop the travel of the control arm before the full extension and compression of the shock absorber is reached (thus giving you a longer life span for the shock absorber).

THERE ARE FOUR MAIN STYLES OF INDEPENDENT SUSPENSION

This is a full independent coil suspension system

Here you can see the use of a quality bump stop inside the coil

It’s vital to double-check all mounts are in the correct position before they are fully welded

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WHAT ARE SOME OF THE PROS AND CONS TO LOOK OUT FOR?

The addition of a grease nipple will prolong the life of the bushes used

Some companies use robotic welders to make sure the suspension mounts are there to stay

INDEPENDENT AIRIndependent air suspension is very similar to its independent coil cousin, except with an air bag in place of the coil. There are three main parts to an independent air suspension being trailing arms, shock absorbers and air bags. Although you can have one of these set-ups without a compressor built in, it would be rec-ommended to install one to aid in inflating and deflating the air bag when needed.

Air bags can be more expensive, but do im-prove the handling capabilities of the camper. A big advantage using airbags compared to any other style of spring is that they can be ad-justed to suit the weight of the camper trailer. Because the weight is different for each trip depending on how long you plan to travel, it is the only way you can have your cake and eat it to. Another bonus is the ability of levelling the camper at a camp site without the need to pile lumps of timber under the wheels. With these advantages come a couple of disadvantages in reliability, not due to the air bag failing, but with the issue of airline joints that if not kept tight can leak air.

Air bag set-ups are normally found on a full range of trailers, as they have the ability

to handle massive weights without any issues. When purchasing a new camper with this style of suspension set-up, it is always recommend-ed to check out the welds on all trailing arms and mounts. These welds should be a consist-ent pattern and show signs of penetration into the surrounding metals. Beware of welds that are inconsistent and lumpy as there is a good chance that they have not have penetrated the metal (very weak set-ups will not hold over heavy corrugations).

The airlines and valves should be positioned out of harm’s way, with a protective covering over all the air lines that will protect them from rocks shooting up from the dirt roads.

Here you can clearly see the airbag suspension components

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The leaf spring can handle more weight then their smaller coil cousins

Slipper pads will prolong the life of a leaf spring

The addition of greaseable shackles will help the longevity of all the bushes

INDEPENDENT LEAFAn independent leaf sprung suspension is a hybrid set-up that gives the load carrying capacity of the leaf spring along with the control of a full independent suspension. This system is by far heavier than others on the market mainly due to the weight of the leaf springs. This system has four main parts: the leaf springs are held in place by shackles and a lower control arm, and to control the up and down travel there is a shock absorber attached to the rear of the control arm. The leaf spring’s general design means that it is perfectly suited to carry heavy loads, the downside being that when the trailer is empty, the spring will hardly move causing the trailer to bounce. This style of suspension really suits heavy camper trailers.

A way to spot a good quality leaf spring is by looking at the leaf packs, and these should have a slipper pad inserted at the end of each spring. Another sign of a quality leaf spring setup is the use of greaseable shackles at each end of the leaf pack; this will lubricate the bushes, reducing wear and tear.

Just like all other independent suspen-sion systems, you should always look at the quality of the welds on all the mounts and control arms. These welds should be a con-sistent pattern and show signs of penetration into the metal surrounding the welds. If you’re looking to purchase a second hand camper that has leaf spring suspension, you should always get under and look at the leaf packs. If they are old and worn you should see that the leaf packs have been rubbing on each other, thus wearing through the metal of the spring.

INDEPENDENT ASYmmETRIC LINk (mC2) The independent asymmetric link suspension (MC2) is one of the rarest forms of suspension set-ups on the market today. This doesn’t mean that it is a bad design, quite the opposite actually, for it was originally designed purely for the Austral-ian military. This system has been subjected to years of research and development and passed all military testing.

This system has two large cross arms (torque arms) that are connected to the chassis on one side and the inner wheel hub on the opposite side of the camper. This reduces the jolt from a bump because of the length of the arms. To support this arm, a radius arm runs forward to the chaise. There is also a coil spring sitting between the chaise and cross arm, and a shock absorber to control the wheels up and down movement. This system is of very high quality and is only seen on a couple of high-end camper trailers today (Note - only the system named MC2 has been tested by the Australian military).

A big advantage with this suspension is the longer you make the control arms, the less the impact on the trailer from a bump in the road. Another bonus is that with the longer arms, the pivot points do not have to twist as much as a con-ventional independent suspension; in return for this the bushes will last up to three times longer than a standard independent suspension that uses coils, air bags and leaf springs.

COILCOIL HAT CHAISE

SHOCK

BACK FRONT

RADIUS ARM

REAR VIEW

TORQUE ARM

COIL

COIL HATCHAISE

SHOCK

COIL SEAT

SIDE VIEW

While a coil controls the height, the shock absorber will control the ride quality

This suspension was originally

designed for the Australian military

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TeChNICalIndependent Suspension

PARTING THOUGHTSWhen it comes down to it, the main reason for running independent suspension on a trailer is to keep the wheels in contact with the road or track as much as possible. Most independent suspensions will do this with ease and are definitely worth the extra money. Before you purchase your camper, you will need to decide whether the suspension under that trailer will suit your needs.

The best way to tell if the suspension is any good is to put it to the test before you buy, hook it up to the back of your truck, and take it for a test drive. Be sure you test it over some rough roads, and if none are available, try driving off the gutter and over speed humps. If the trailer bounces all over the place in these conditions, there is a good chance it will be pretty useless over corrugations.

Another way to tell if this suspension is worth the extra money is to look at the quality of all the components. Things like shocks and coil springs are hard to pick, but the leaf sprung suspension should have a rebound spring if the camper is to hold any decent weight, and the leaf packs should have slipper pads between and at the end of the individual leaves, which will allow them to slide back and forth without rubbing metal on metal.

The control arm pivot points should have bushes in them and have the ability to be greased; some pivot points on cheaper trailers can often have metal on metal joints that will wear quickly. The control arms and all mounts should be substantial, and the welds holding them should be even and show some sort of penetration to the metals that they are to bond. If welds look like small ball bearings and have gaps all over the place, there is a good chance they will not last and these should be avoided.

The advantage of having quality suspension under your camper is that you will be able to travel over rough roads faster and safer than with a poor quality set-up. Just think, will the eggs last the trip or will you have them scrambled in less than a day’s drive. Good luck finding that camper trailer and we hope to see you out on the tracks.

CONTACTSWe would like to thank to the boys from Vehicle Components, Xtrail and Complete Campsite for sharing their expertise throughout this article.

Xtrail campers Phone: (03) 9761 7373 www.xtrail.com.au

Vehicle Components Phone: (07) 3624 3810 www.vehiclecomponents.com.au

Complete CampsitePhone: 1300 859 083 www.completecampsite.com.au

GIC Camper TrailersPhone: 1300 CAMPERS (1300 2267 377)www.giccampertrailers.com.au

A good weld is always a good sign of a quality built suspension

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