Independent suspension systems for camper trailers – what are the

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techNICAL
Independent Suspension
W
hen 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 manufacturer 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 market, but over time they have grown to become
one of the most sought after upgrades. There
are many different versions of suspension setups – from the older style of leaf springs with a
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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 independently of each other.
There are four main styles of independent
suspensions available: independent coil, independent 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 suspension 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 suspension package will best suit your needs.
Independent control arms
awaiting installation
It’s vital to double-check all mounts
are in the correct position before
they are fully welded
INDEPENDENT COIL
Independent 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 unsusceptible to damage or wear and tear, but
compared to the cheaper leaf sprung suspensions 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 common 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 using 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 suspension set-ups.
This suspension works well with all
weighted camper trailers from 450kg to
1700kg. Things to look out for when purchasing 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).
Here you can see the use of a
quality bump stop inside the coil
This is a full independent
coil suspension system
THERE ARE FOUR MAIN
STYLES OF INDEPENDENT
SUSPENSION
091
techNICAL
Independent Suspension
Some companies use robotic welders to make
sure the suspension mounts are there to stay
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
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INDEPENDENT AIR
Independent 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 recommended to install one to aid in inflating and
deflating the air bag when needed.
Air bags can be more expensive, but do improve the handling capabilities of the camper.
A big advantage using airbags compared to
any other style of spring is that they can be adjusted 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
Here you can clearly see the
airbag suspension components
to handle massive weights without any issues.
When purchasing a new camper with this style
of suspension set-up, it is always recommended to check out the welds on all trailing arms
and mounts. These welds should be a consistent 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.
Slipper pads will prolong the life of a leaf spring
The leaf spring can handle more
weight then their smaller coil cousins
INDEPENDENT LEAF
An 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 suspension systems, you should always look at the
quality of the welds on all the mounts and
control arms. These welds should be a consistent 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.
The addition of greaseable shackles
will help the longevity of all the bushes
techNICAL
Independent Suspension
COIL HAT
SIDE VIEW
CHAISE
SHOCK
COIL
TORQUE ARM
COIL SEAT
COIL
BACK
CHAISE
COIL HAT
FRONT
While a coil controls the height, the shock
absorber will control the ride quality
REAR VIEW
SHOCK
RADIUS ARM
Independent
Asymmetric Link (MC2)
This suspension was originally
ary
designed for the Australian milit
94
The independent asymmetric link suspension
(MC2) is one of the rarest forms of suspension setups 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 Australian 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 conventional 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.
A good weld is always a good sign
of a quality built suspension
PARTING THOUGHTS
When 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.
CONTACTS
We 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 Campsite
Phone: 1300 859 083
www.completecampsite.com.au
GIC Camper Trailers
Phone: 1300 CAMPERS (1300 2267 377)
www.giccampertrailers.com.au
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