Off-Road Caravan Suspension Design eBook

insert image here:
150 x 80mm
Suspension Design
for an
Off-road Caravan
www.kimberleygroup.com.au
Copyright Kimberley Kampers Pty Ltd
20140103
Suspension can be raised easily before a water crossing with the
ultimate in auto-ride height remote control air-suspension

2 Guide to Suspension Design for an Off Road Caravan
kimberleygroup.com
You can travel on virtually any road with any suspension.
People do the Cape towing a low cost box trailer and tent.
However, the poorer the suspension, the slower you will need to trav-
el and take less load. It is all about energy. It is also about stability.
The faster you travel and the heavier the caravan, the more important
it is to have good suspension.
If you want to travel long distances on the highway and then long
distances in difficult off-road conditions with off-road caravans and
camper trailers, then you should understand the impact of suspen-
sion design.
You deserve to have the smoothest travel with the best stability and
the lowest fuel consumption possible… at the best pace!
There are many design variables to support this but none has a
greater impact than suspension design.
Great suspension design can’t be done alone on a drawing board; it
needs analysis of a dynamic model with the vehicle to get the “design
constraints” right. This is something few manufacturers understand.
The core question then when investigating your travel requirements
is to ask just how much of Australia do you want to experience?
“Experience” is more than just looking. It is not just soaking up the
beauty of Australia, it is also living and sharing experiences.
That’s great, but is it worth the additional cost?
Have a read through this eBook to decide.
How much of Australia do you want to experience?

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It is illegal to copy or reproduce
any part of this document without
the express approval of Kimberley
Kampers Pty Ltd
Table of Contents
How much of Australia do you want to Experience?
1. Independent Suspension Innovation in 4WDs since 1970’s
2. Reliability
3. Digital Age adds to Stability as well as Reliability
4. The Difference with Caravans and Trailers.
5. Camper Trailers and Caravans pre-2000
6. Coil Springs
7. Coil Springs and Stability
8. Air-Springs (Air-bags)
9. Premium Air-springs
10. Roll Stability and overall Design
11. Ride Quality and Lowest Unsprung weight
12. Lowest unsprung mass of any suspension
13. Air Suspension Control Systems
14. Ride Height controlled Air Suspension Systems
15. Changing a Wheel /Tyre without a Jack
16. Driving on 3 Wheels in an Emergency
17. Anti-Sway Bars
18. 5 Year Warranty

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Suspension innovation is probably the most important factor in a
4WD’s off-road superiority.
In 1970, at a time when almost all 4WDs used primitive leaf springs,
Range Rover pioneered the use of soft, long travel coil springs on all
four wheels. This caused a lot of skepticism among off-road journalists.
The result was a delay until 1987 introducing this feature to the USA
for fear the market may not accept such innovation. The benefit of ex-
treme axle articulation became clear to everyone.
Other 4WD manufacturers started incorporating it some 5 years later.
No one could then believe they were ever skeptical and this innovation
became the norm!
Then in 1993, Range Rover suspension design took another leap
ahead into the next generation of innovation: electronically controlled,
self leveling, variable height pneumatic suspension. (This is where we
are today with off-road caravan air-suspension, some 20 years later)
This gave the driver the ability to reduce ride height for high speed
cruising, increase it for off-road clearance, maintain a level ride regard-
less of load, and maintain articulation. The staggering capabilities of
this system, in combination with the simultaneously introduced elec-
tronic traction control, took the 4WD world by surprise.
Now the Range Rover suspension innovation has progressed: The air-
springs are cross-linked (left to right) when off-road, reducing the effec-
tive spring rate to near zero. This not only softens the ride but increas-
es the ground contact force and traction considerably on a drooping
wheel. It also makes the independent setup simulate the articulation
motion of a beam axle, getting around the usual criticisms of reduced
effective off-road clearance on uneven terrain that independent sus-
pensions usually receive.
This is where we are heading at Kimberley but it will take some devel-
opment and test time to get there.
Independent Suspension Innovation in 4WDs

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Aside from the advantages of much-improved ride and steering con-
trol over bumpy terrain, one of the difficult design constraints is the
load on the vehicle and travel conditions.
Using soft coil springs improves the ride until the vehicle load goes
over the design limit and the coils are struggling to hold up. Then
trouble is on the horizon.
When air-springs (air-bags) were first introduced, the story was
similar. The air-bags were rated at a maximum pressure and heavy
vehicle loads pushed past this.
Although Range Rover were using major manufacturers like Fire-
stone for the actual bags, the fittings and compressor were not al-
ways as reliable for the high duty rate.
Overall, the market accepted the innovation but reliability stories
held back overwhelming acceptance. The author has had 4 Range
Rovers and whilst only one required some minor air suspension re-
fit, it was expensive and could not be done “in the bush”.
The designers have now understood that it is not just the actual “air-
bags” that are the weak link in the system but all the fittings, com-
pressor and tank that go with it.
Reliability is now up to par with mechanical systems. Prices are now
reasonable especially replacement air-bags which can be sourced in
many locations around Australia.
Reliability

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Digital Age adds to Stability as well as Reliability
The advent of computers embedded in vehicles has not only extract-
ed that extra engine efficiency but significantly improved stability in
today’s 4WDs.
High end models can be equipped with an air suspension system
featuring self-leveling, ride-height control and stability management.
Stability Management is an electronic damping control system. It
offers continuous adjustment of individual damping forces based on
current road conditions and driving style – all from the centre console.
During performance driving or heavy off-road use, there is an in-
creased tendency for the body to sway. Stability Management pre-
vents this from happening, thereby improving stability and occupant
comfort. The system uses a series of sensors to monitor the move-
ment of the body. It also gathers data on lateral acceleration; steering
angle, brake pressure and engine torque and modifies the damping
force on each individual wheel in accordance with the selected mode.
Stability Management remains active at all times. It automatically
adapts to the prevailing driving conditions, enabling greater car con-
trol and improving comfort and safety.
The auto-ride height air-suspension from Kimberley is digitally con-
trolled and has a LCD display and optional hand held remote control.

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Are trailers, caravans and campers trailer different in their design
requirements to 4WDs?
Yes, absolutely.
The differences are so great, there are few vehicle suspension ex-
perts who understand the nature of a towed trailer.
It is one of the reasons for writing this eBook. There is virtually noth-
ing published regarding “off-road caravan suspensions” and little that
can be found on the Internet other than individual stories.
We started by studying the theory of suspension in commercial trail-
ers which is a closer starting point than most people realize.
Our motto on innovation is: “Without understanding the theory, expe-
rience will not teach”. So it has taken years of experience layered on
top of the theory of suspension in trailers to get to this point.
You will need to read to the last chapter to gain insight into the differ-
ences.
We believe you cant “add on” top of the line suspension. It has to be
part of the design right from the beginning.
So lets look at our journey to get to this point!
The Difference with Caravans and Trailers.

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Leaf springs were common-place pre-2000 with most focus on the
dampening of shock absorbers over the difficult terrain.
Independent suspension was
being used in higher end camp-
er trailers.
We had our own experience with
leaf springs which we fitted to
our “Escape” and early ”Sports-
RV” models. The photo on the
right shows the electric drum
brake hub and Old Man Emu
shock absorbers with a 7 leaf
spring. Note the red “bump stop”
was used in the leaf spring.
This set up resulted in no spring
failures.
However, the load range for this
type of suspension is limited.
In the photo you will see a
300kg+ quad bike loaded on the
front of the author’s Kimberley
Kamper that had leaf suspen-
sion. There was a 300mm jump
to get onto this bridge!
In poor roads and conditions,
travel speed slowed to a snails
pace and the rig jumped around like a kangaroo. Every bump was no-
ticed and the tie down straps re-tensioned every 100 klms.
Camper Trailers and Caravans pre-2000

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Whilst this is an extreme weight, it is the extremes that test the the-
ory of our designs. After towing this, it was decided to leave the leaf
springs and standardise on independent suspension for every mod-
el. This has been the case since 2005.
The one benefit of leaf spring suspensions is higher inherent roll sta-
bility. This is now overcome and in fact surpassed in the coil and air
suspensions by adding anti-sway bars.
The coil springs on a Kimberley Kamper go deep into the cups and
the upper mounts for secure positioning. Inside the coil spring is a
sewn web strap to prevent over extension of the shock absorber.
In this photo you can also see secondary “bump stops” to also limit
compression of the shock absorber. These secondary bump stops
are polyurethane and compress at a higher spring rate to absorb
any huge thumps on the suspension!
The shock absorbers in this photo are Fox mono-tube.
Coil Springs

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The main secret to the amazing off-
road traction of independent suspen-
sion with coil springs is to use excep-
tionally soft springs.
However in a 4WD with 4 available
wheels, it is not uncommon to have
one off the ground with the vehicle
weight on the other 3. In a trailer, this
rarely occurs. And this is one of the
major differences to 4WDs : the high
load is shared to each trailer wheel as
they are rarely off the ground.
As a result, the coil springs on the
trailer have to be matched to the
load. If you travel on one trip with a boat and outboard or quad bike,
then take the next trip without these additions, using the same coil
springs will be an uncomfortable ride.
At Kimberley we have 4 different grades of coil springs for models
across the range. Each grade is painted a different colour. Some are
interchangeable with different strap lengths.
The lesson we learned in the first release of the Karavan was finding
the right balance between “soft” and the customers load.
The secret is increasing the coil travel length in high load applica-
tions. Why is this key?
To take a high load, longer softer springs just compress more.
Although this will change the travel height, the softer coils maintain a
low spring rate which is a big advantage in ride comfort and control.
We design for 170mm travel in the Karavan and Eco-suite. A little
less in the Kamper and Kruiser.
Coil Springs

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We are not aware of a coil spring that has “broken” but we have
seen a few that have “drooped” over the years (8-10 years!) be-
cause of a high load on these softer springs.
Coil springs are easy to replace and inexpensive.
However, in on-road travel, soft coil springs alone can introduce
sway to a trailer.
For camper trailers, increasing the ball weight compensates for this.
So having ALL the load capacity between the axle and the hitch
means that as customers load their trailer, the increase in ball weight
will off set any stability issues from softer springs.
For high load applications with boats and bikes, heavier coil springs
are used.
Rear mounted wheels, bicycles and other heavy point loads are in
advisable on trailers with soft long travel coil springs.
For off-road caravans, there is the option of adding an anti-sway bar.
These are fitted to the independent suspension in a similar way to a
vehicle. They can be easily disconnected for off-road use. These are
NOT the same as the weight distribution hitches at the front of the
trailer. The anti sway bars are hidden up underneath between the
suspension and the chassis. There is a choice of 2 sizes.
With some 4WD vehicles, particularly if their suspension has been
changed, you may need the heavier anti-sway bar fitted with the
softer coils that are on the Kimberley Karavan.
In a nutshell, coil suspension on an off-road caravan is designed:
• To be as soft as possible to maximize available vertical wheel
travel and articulation
• To have long travel length to take the load on the off-road cara-
van or camper trailer.
And if it is an off-road caravan
• To work with anti-sway bars added to the independent suspen-
sion for highway travel at speed.
Not unimportantly, soft coil suspensions also tread lightly and result
in less environmental impact.
Coil Springs and Stability

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This table is the coil suspension setup in the Kimberley Range:
Type
Trailing Arms Reverse swing with sleeve bushes, dual lubrication.
Stub Axle position can match vehicle wheel tracking width.
Toe in and Toe out Alignment
5 Year Warranty transferable to next owner.
Coil Springs Cold rolled Australian made, Anti spin tab on lower offset
cup. Lower cup angled for approx 90 degree in mid point
Bump Stops Kimberley design with tapered cone, Hi impact polyure-
thane. Insert bolt. Easily replaceable
Shock Absorber Twin Tube or Mono-tube, 50-50 setting, dust protector. Mo-
no-tube can be rebuilt.
Bushings All stainless steel spherical busings on mono-tube. Polyure-
thane busings on twin tube.
Over extension Webbing Strap, Quad sewn, tested with bushings
Hubs For Disc Brakes: 2 piece with 12mm thick discs, matching
stud pattern to most vehicles.
For Drum Brakes:1 piece and selected stud patterns.
Brakes Choice of Electronic Disc or Electric Drum
Coil Springs

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Firstly, Air-Springs have some negatives:
• They cost more than steel coil springs
• They are less reliable that steel coil springs
• Reduced roll stability
But some huge positives:
• A soft “magic carpet” ride on all trailers, and
• Increased stability and safety on tandem caravans as the height
can be leveled to match the vehicle regardless of the load.
If your caravan has air-suspension, you can drive faster and more
confidently on typical rough roads or corrugations, where higher
sprung caravans may be reduced to a kangaroo-hopping crawl.
There are concerns of gibber and stone damage to air-bags, howev-
er, you can change out an airbag in less time than a coil spring. The
price of a spare air-bag from Kimberley is less than $300. So you
have the peace of mind of having a spare available.
In the photo on the
right, we have the
air-bag deflated so
you can see the
length of the travel
in this Kimberley
Karavan.
The bump stops
are installed exter-
nally for maximum
“thump” protection.
Air-Springs (or Air-bags)

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So is the higher price of air suspension and the replacement cost of
air-bags worth it?
Obviously, as witnessed in nearly all premium 4WD’s, the air sus-
pension system conveys many benefits over an ordinary fixed coil or
leaf suspension.
• Increased ride control in varying conditions
• The availability of an instant “lift” for off-road operation,
• The ability to change height to match the load
• The progressive nature of air-springs reduces the chance of “bot-
toming out” when hitting a bump too fast.
• The ability to lower either side when in camp to level the trailer or
caravan
• When lowered from standard height to highway or low profile
mode, the aerodynamics are improved and there is increased fuel
efficiency.
For the Kimberley Kruiser, we found the fuel economy difference
between “normal” height and “low travel” height resulted in 0.96 Li-
tres/100klm less fuel consumption.
So on a 20,000 klm trip, that is 180 litres of fuel which is about $320
saving.
However, if you are going to consider air-suspension, then consider
the new Premium air-springs from Kimberley. These are a step up
from the normal air-bags and offer significant advantages:
Air-Springs

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There are 2 major types of air-springs available for tow-able trailers
and caravans.
• Fixed Diameter piston operated air-bag
(Standard)
• Variable Diameter piston operated air-
bag (Premium)
The Variable Diameter (Premium) one costs
more yet has improved benefits.
To explain how an air-spring works, we will
concentrate on how the variable diameter
unit operates and what the difference is.
If you look at the factory supplied air-sus-
pension in a Land Rover or Range Rover,
the air-spring piston widens towards the top. Photo on right is au-
thor’s 2012 Model TDV8 Range Rover air-spring. The white lines
highlight the piston profile. The Wheel has dropped as the photo was
taken on a hoist (just for this article)
The wider diameter of the piston at the top effectively stiffens the
suspension with a higher spring rate as vehicle height increases.
The piston also widens slightly at the bottom but not progressively.
This gives a harder ride off-road and a softer one at highway speeds
unless the airbag is right at the bottom of it’s travel.
This is an example of a difference in the suspension of a trailer or
off-road caravan. In our opinion, the Range Rover setup is the oppo-
site of what is needed for the trailer or caravan!
On the new Kimberley Premium air-spring, the air-spring piston
design has sensibly been modified to reverse this situation, giving
softer spring rates in high profile and stiffer rates in low. This makes
a lot more sense to us and lets explain why:
Premium Air-springs

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The Premium Air-Spring is a totally new design with a two-stage pis-
ton that widens out to a bigger diameter at the bottom.
• It has only 3 components instead or 4
• The piston is widened at the bottom for increased spring-rate
• The “effective travel length” is longer as there are fewer compo-
nents. (photo below does not show the full travel on lower mount
as we slid the air-bag over the bottom section too far also hiding
the length of the piston)
• The upper and lower mounts are CNC machined from 6061 Alu-
minum and polished where the air-bag rolls over. (far superior for
wear compared to polyurethane in standard air-bags)
(The photo below shows a “mock up” during manufacture before the
clamp ring is placed. The author slid the air-bag too far down the
lower piston in this photo to get a comparable length as the standard
air-bag for measurement purposes)
Premium Air-springs

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Premium Air-springs
How does this shape change work?
The air “bellows” rolls over the lower piston.
With a variable diameter piston design, the bellows folds over the
larger diameter section of the piston when in low profile (highway)
mode. However, it reduces to the longer narrower diameter for most
of its length. See the circled larger diameter in the photo above.
The smaller diameter piston cross-section displaces less air for a
given amount of travel, giving a softer spring rate. Conversely, when
the bellows have rolled lower and are operating on a larger piston
cross-section, a bump in the road produces a larger displacement of
air, effectively increasing the spring rate or stiffness.
This means that when the suspension sits at “standard” or “high”
travel height, the spring rate is less giving more travel. This is great
for low speed and off-road conditions.
Finally, the resultant air-suspension has a longer effective active pis-
ton which provides 40-50mm more travel at a lower rate.
The result is a noticeably smoother ride when the suspension is set
to “normal” or “high” with noticeably more control in highway travel at
“low” mode, and more usable wheel travel.
The secret of the new Kimberley Premium air-springs lies in the
custom-made lower piston which is CNC machined out of a solid
aluminum billet, specially shaped to vary the spring rates according
to conditions.
For example, the narrower top zone reduces the spring rate in high
mode, greatly softening the ride. In standard mode, the bellows will
touch on the widening diameter at times and yield what we regard
as a “normal” rate. The fatter bottom section gives a spring rate of
150% times normal in low or highway mode.

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Another feature built into the new Premium Air-spring is significantly
longer travel -- with 170mm extension achieved via the longer piston
and special bellows.
However, we have designed the new variable air-spring to be
interchangeable with the standard air-spring so that spares and
even third party “off the shelf” air-bags can be purchased and
used if required.
In a nutshell the design features of an air-spring are:
• Long travel is still preferred like the coil spring
• Operate in a range of 3:1 on pressure only
• Standard air-springs use polyethylene blocks with nut-serts for
securing
• Premium air-springs will be precision CNC-machined from 6061-
T6 aluminum.
• Premium air-springs will have at least a 1.3:1 spring rate increase
from increased diameter
Photo above is the actual CNC machine upper mount of the Kimber-
ley Premium Air-Spring. It shows the dual upper mounts and air-line.
Premium Air-springs - Release Date January 2014

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Air suspension is not just a matter of putting air-bags under indepen-
dent trailing arms and the job is done! A caravan loses its ability to
resist rollover when the tires on one side lift off the ground.
Chassis flexibility, the suspension design, tire and axle deflections
are all factors that need to be considered when determining a cara-
van’s roll stability.
Roll stability can largely be determined by the height of the center
of mass of the trailer, the axle track and the softness of the suspen-
sion. For example:
• Changing the caravan’s axle track from 1800mm to 1950mm can
improve its roll stability by nearly 10 percent.
• Reducing the height of the caravan’s center of mass by 150mm
by lowering the air-springs can also improve roll stability by a sim-
ilar amount.
• Increasing the air-spring pressure by 50% will also increase sta-
bility.
However, lowering the centre of gravity and therefore the air-springs
both reduces the height AND reduces the pressure. These fight each
other on stability. Without a way to compensate for this, the reduced
air pressure in the suspension will allow more “rolling” by the cara-
van, particularly at speed when cornering. The lowest pressure we
use is 18-20 PSI.
For this reason, the suspension design needs to have an anti-sway
bar as standard for off-road caravans with air-springs but it is not
needed for the very low centre of gravity camper trailers.
Field testing resulted in 3 different anti-sway bars from 16mm to
20mm diameter. Generally, the lightest bar that gives the required
stability should be used.
We would not ship a 2.5 tonne + off-road caravan with air suspen-
sion without an anti-sway bar. Should the air-bag pressure reduce
because of a lower user setting or a leak, a resultant roll would be a
major safety issue!
Roll Stability and overall Design

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The commercial trailer industry measures ride quality by the degree
of isolation the suspension provides the vehicle from road inputs
without compromising vehicle control.
Minimizing road forces and vibration results in less discomfort and
lower vehicle and trailer maintenance cost.
What factors control ride quality?
Major influences on trailer protection include the suspension’s natu-
ral frequency and travel. In general, suspensions with lower natural
frequencies reduce the forces transmitted to the trailer and improve
ride.
Natural frequency comprise the spring rate of the suspension and
the amount of un-sprung weight the suspension is supporting.
Air suspensions are capable of achieving very low natural frequen-
cies and providing very high levels of protection.
• Typically, air-suspension natural frequencies are below 1.5 Hz.
• Typically, mechanical suspensions have natural frequencies that
range from 2 to 5 Hz, depending on payload.
The second factor in this equation is the un-sprung weight. Think
of this as how a wheel controls the trade-off between a wheel’s
“bump-following” ability and its vibration isolation.
Bumps in the road cause tire compression — which induces a force
on the un-sprung weight. The un-sprung weight then responds to
this force with movement of its own. The amount of movement, for
short bumps, is inversely proportional to the weight. A lighter “wheel/
hub/brake/tyre set” which readily moves in response to road bumps
will have more constant grip when tracking over an imperfect road.
For this reason, lighter “wheel/hub/brake/tyre sets” have a lower res-
onant frequency and give better road holding.
Ride Quality and Lowest Unsprung weight

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In contrast, a heavier “wheel/hub/brake/tyre set” (which moves less)
will not absorb as much vibration. The irregularities of the road sur-
face will then transfer to the caravan through the geometry of the
suspension and hence ride quality is deteriorated. For longer bumps
that the wheels follow, greater un-sprung mass causes more energy
to be absorbed by the wheel/hub/brake/tyre sets and makes the ride
worse.
So good suspension design requires:
• lowest spring resonant frequency which is achieved with air-
springs
• lowest “unsprung weight” which is achieved with disc brakes and
air-springs. This combination is typically half the weight of the
equivalent drum brake, coil spring combination.
The shock absorbers dampen the spring (coil or air) motion but also
must be less stiff than would optimally dampen the wheel bounce.
The wheels vibrate after each bump before coming to rest. These
motions form the “road corrugations” which we hate. It is the sus-
tained wheel bounce in subsequent vehicles that enlarges the corru-
gations and deteriorates the road!
High un-sprung weight also exacerbates wheel control issues under
hard acceleration or braking. Vertical forces exerted by acceleration
or hard braking combined with high un-sprung mass can lead to se-
vere wheel hop, compromising traction and steering control.
Ride Quality and Lowest Unsprung weight

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So how has Kimberley perfected such a low un-sprung mass on the
“suspension/ wheel set” over the last 10 years?
The first item to focus on is the wheel hub and brake assembly.
The disc/brake hub we use and the PBR disc brakes are half the
weight of the 12inch Electric drum alternative.
Then we use lower weight Mono-tube alloy shock absorbers, and
the lightest weight performance air-springs or coil springs.
The bump stops and suspension straps and are our own design at
the lowest possible weight.
The shock absorbers are mounted in the optimum perpendicular po-
sition and the mono-tube shocks use stainless steel bushes for resil-
ience in corrugations. (If you see dual shock absorbers at an oblique
angle; the units aren’t as effective in this position so 2 are used with
the result of higher un-sprung mass).
Finally, the high tensile steel trailing arms have a unique curve pat-
tern for the best weight/performance.
The benefit to customers is not only better vehicle control and better
ride but a 5 year warranty on the chassis and the trailing arms. They
are well looked after in a Kimberley!
Lowest unsprung mass of any suspension

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Pressure based ride height control (P)*
Pressure passes
to the air-springs
through individual
wheel control valves
as well as pressure
control valves (Pad-
dle Valves) that are
set as drivers side and passengers side.
Back up manual air control is installed (see
valve fillers in photo below). Gauge is co-
loured needle on dial and twin needles show
pressure on each side.
Single Axle Tandem Axle
Simple no-frills individual wheel air-bag pressure set-
ting from air line and vehicle based compressor
(No automatic control fitted ) * check inclusions.
Yes
Manual
Difficult
Individual Wheel height control from control panel P,H P,H
Manual over-ride control of air-bag pressure (and
height control) should central control fail
P,H P,H
Driver’s side or Passenger’s side control of ride height
with specific pressure on each side
P P
Ride height control of each wheel automatically moves
to one of 3 pre-set heights based on vehicle. This is
calibrated to your vehicle.
H H
Ride height control automatically sets level between
front and rear wheels in tandem axle.
n/a H
Remote control of Ride height by hand held controller H H
Drive on 3 wheels in emergency? P,H P,H
Change wheel without jack? (Road conditions and
general safety permitting)
P,H P,H
Drop to ultra-low level to reduce height for garage M,P,H M,P,H
Air Suspension Control Systems
Height based ride height control (H)
Pressure passes
to the air-springs
through individu-
al wheel control
valves as well as
pressure control
valves. Each wheel’s pressure control valve
is connected to a ride height connecting le-
ver on each individual independent suspen-
sion arm. 3 touch buttons set the ride height
which can be calibrated to your vehicle’s
ride heights. Gauge is digital.

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Ride Height controlled Air Suspension Systems
There is a good story on automatic ride height control with air-
springs. The system can be used for either single or tandem axles
but it really has big advantages with tandem axle off-road caravans.
One of the major impacts on towing stability in a tandem off-road
caravan is keeping it perfectly level to match the vehicle towing
height… in all conditions. To understand this in full, read our eBook
on towing stability.
However, changing the travel height has to match the vehicle height.
With the standard pressure based system, this is tedious to get ex-
actly right.
The ride height automatic controller will allow you to set the height
and have it calibrated to exactly match the vehicle. Then it doesn’t
matter how much water is on board or other loads, the air suspen-
sion will go exactly to that height.
We ship systems with low, normal and high height settings and cali-
brate the low to the vehicle in highway mode, the normal to off-road
mode and the high for when maneuvering slowly over rocks or re-
versing around a ditch. It is also great for water crossings.
What happens is there are “ride height” levers on each independent
suspension arm and the pressure required per air-spring to be per-
fectly “level” is maintained.
When in camp, you over-ride the pre-selections and manually ad-
just each wheel height to get the caravan perfectly level. Then when
about to get back on the road, a single touch will set the ride height
again. If you change the tow vehicle, you will need to re-calibrate the
settings. This takes 10-15 mins.

kimberleygroup.com
The video direct link is: http://youtu.be/oX6rPOSWOgE
or click on the image below:
Video of Digital Auto-ride height control of air
suspension

kimberleygroup.com
Getting a flat tyre, changing a spare wheel in a tandem off-road caravan
There is nothing more frustrating that a flat tyre. Even more worrying is
when you are on a narrow road with Road Trains. If you keep driving,
the wheel as well as the tyre can be severely damaged.
Convenience is available though with the Kimberley Kruiser which has
close-coupled independent air suspension.
This means that one of the
suspension arms can be kept
“up” while you either drive on
3 wheels or simply change the
wheel/tyre without the need of a
jack. How is this done?
It cant be done with any
“walking beam” or “Simplicity”
suspension, well not very easily,
if at all. The 4 independent
suspension arms on the
Kimberley off-road caravan
have independent air suspension at each suspension arm. Individual
valves allow you to drop all 4 arms down to the “bump stops” and then
raise only 3 of them leaving the 4th one “up in the air”.
To test this, we demonstrated the exact process to a customer who
wanted the facility of changing wheels/tyres without the need of a jack
for the off-road caravan.
Changing a Wheel /Tyre without a Jack

kimberleygroup.com
There may be situations where you can’t change a wheel easily
however, like a creek bed or difficult terrain.
In those circumstances you should be able to drive off on only 3
wheels with one raised and then change at a convenient time.
To test this, we drove from Coffs Harbour to Penrith on only 3
wheels with a Black Caviar model off-road caravan. The result was
great. The Kruiser is designed so that half the maximum axle load
can be taken by one wheel and one tyre.
What happens if I stake an air suspension chamber?
You can drive on 3 wheels to somewhere safe and convenient. Or
you can carry a spare with you.
Driving on 3 wheels in an emergency
Anti-Sway Bars
This photo shows the anti-sway bars fitted up into the top of the indepen-
dent suspension with linkages on either side.
2 different sizes are available.
The discussion on anti-sway bars is in the previous chapters.
At Kimberley, we warrant the chassis and suspension arms for
5 years, that is how confident we are with our product. We have
over 6,000 chassies rolling around in remote places and have
an excellent reputation for durability and product quality.
5 Year Warranty

kimberleygroup.com
An Interesting Air-Suspension set up
by an Individual
This is an interesting air-suspension setup obtained from an individual’s photo on
the net. (for privacy no link available)
Great to see someone trying to get into air-suspension, but...
The educational question is what is vulnerable in this setup?
• Assume bump stop is inside airbag, what is effective travel?
• Upper airbag mount not clear but looks lateral, not overhead.
• No chassis support directly above air-bag top mount
• Shock absorber at a strange angle, and at this angle 2 may be needed.
• Shock absorber mounts are at 90 degree to each other
• Tube size on suspension arm looks under-sized
• Open tube end on suspension arm

Off-Road Caravan Suspension Design eBook

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