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Caravan Buyer’s Guide - Chassis & Suspension

Posted: Friday, April 12, 2013 at 1:27:52 PM EST by

From last week’s post we now want to share about the chassis and suspension of a caravan and fifth wheeler and how they complement each other.

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Chassis designs have not changed much over the years.

The main change has been to utilize lighter materials and manufacturing techniques to keep the weight to a bare minimum, yet upholding maximum strength and durability.

Some manufacturers have gone too far with this process and have had major failures with fatigue, cracks and bending.  A cracked chassis is an unsafe chassis.

There is a grey area on what is considered an ‘off road’ caravan, and how capable that caravan performs before there are problems.

You may have seen how some manufacturers have tackled this.  They normally ‘double-up’ on the main rails of the chassis, and in reality you are doubling up on weight and costs as well.

In our previous post we talked about body construction.  The body plays a major part in how the chassis is designed.

Because of the tensile strength in the composite panels, the body practically supports itself.  Therefore, the body needs less support from the chassis.

The chassis has been designed to give strength and support exactly where it is needed.  We are able to drop the weight down and concentrate on the important fixtures that need the support, like the hitch, tanks and suspension.  

A chassis should be individually designed for the body of the caravan and its floor plan.  The chassis is then fabricated using super-gal RHS steel framework and re-enforced sheet metal, making it super strong and sturdy.  A laser leveling system to ensure all is square, level and at minimum tolerances is a practice undertaken by only the serious caravan manufacturer.

In comparison to chassis design, suspension design has changed over the years.

There is now a larger variety of different types of suspensions on the market.  Manufacturers and customers are seeing the benefits in their freedom of choice.

The biggest change has been the addition of independent trailing arm suspension with air springs.  The use of Air Springs has been standard in the truck and bus industry for several years as a way of protecting passengers, loads and even the road surface.

This type of suspension has many advantages over traditional coil, torsion or leaf springs.  Air suspension allows a soft spring rate with the ability to maintain constant ride height.  The independent arms mean that bumps experienced on one side of the van are not directly transferred to the opposite side.  As the wheels ride over undulations they stay perpendicular to the road surface.

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Another benefit is the ability to level the van across slopes when parked.  The Air Springs themselves are able to be adjusted by the flick of a switch to keep constant ride height no matter what load is being carried.  In doing so the internal air pressure changes and so does the spring rate giving a perfect ride for all load conditions. The onboard Air Pump and Tank provides a ready supply of compressed air for pumping up tires etc.  Literally riding on air, this suspension provides the best protection for your caravan.

Buying a caravan or fifth wheeler is a major investment of your hard earned cash.  Be sure to do your research and ask experts like Southern Cross if you have any questions.


johnbeattie_author

About the Author : John Beattie Google Plus

John is the Manager at Southern Cross Caravans. Australia's Premier Manufacturer of 5th Wheelers. He and his father Barry have travelled the length and breadth of Australia including some of Australia's most ruggered 4WD off-road tracks. All the time towing one of their ruggered Southern Cross Caravans. This field testing has led to Southern Cross Caravans being one of the sturdiest yet most comfortable 5th Wheeler Caravans in the world... Nice Work if you can get it.

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Comments

Comment by: ANDREW SMALL
Aug 21, 2014 at 5:27 PM
Hi there,we are planning on buying a s/h poptop 16..18 ft,that has decent independant suspension,capable of handling dirt roads..no extreme offroad stuff. Can you list what brands to consider? Thanks. Andrew Small.
Comment by: Jackie Aitken
Mar 30, 2014 at 9:56 AM
Hi John, we are buying a 22 ft caravan Tare Weight: 2652Kg.wondering what kind of suspension you would recommend . We have been told rocker roller would be best. Mostly on road but will do some off road. Regards Jackie
Comment by: Richard Wheeler
Feb 17, 2014 at 7:32 PM
Hi, We are looking at buying our first caravan. I'm not sure if you can comment on this but here goes. One van we are considering is Kingdom Kensington Mark1. Reasons are they have a very good finish inside and their weight is only around 2 tonne for a 19'6" van. I'm looking at independent coil suspension with rebound straps so as to not lose any coils. I believe the frame would have to be stronger where the suspension would be attached. We know Kingdom have only been around for about 5 years, but if the product is of good quality & warranty service is covered then this shouldn't be a problem. Do you believe their framework will be ok with this type of suspension? If you cannot comment we understand. Cheers, Richo.
Comment by: Lindsay
Feb 17, 2014 at 5:24 PM
We are considering buying an off-road van about 18' long and have come across various suspensions of the type: trailing arm/springs/shocks. One van we looked at was 2.5 tonnes weight with this type of suspension rated at 2.5 tonnes. Am I correct in thinking such suspension will not be strong enough for the van once we load it with 180kgs water plus 300 to 400kg of food, camping equipment etc? If so, should the rating be at least 600 or 700kgs more than the van's weight or is there some rule-of-thumb relating the rating of the suspension to the weight of the van?
Comment by: Southern
Cross
Oct 14, 2013 at 2:56 PM
Hi, yes we can help you with technical information and advice. We custom build from the ground up, so this means we should be able to answer almost any question you can throw at us. You can either call us on; 07 3200 6924, or e mail us on; sales@southerncrosscaravans.com.au or go to our website; www.southerncrosscaravans.com.au and follow the prompts.
Comment by: Ellen Bolton
Oct 11, 2013 at 3:53 PM
Hi John, Is there somewhere I could purchase or get advise on information regarding technical, structure layout, materials and sizes, external and internal Wall and floor layouts for a modern caravan approx. 32foot. Thanks and regards Ellen Bolton
Comment by: Southern
Cross
Oct 8, 2012 at 3:14 PM
Different suspensions are used for different applications. A heavier chassis and suspension should be more robust for harsher conditions, but, it will be heavier to tow and will bounce around more. Ultimatly, Airbags instead of springs will soften the ride Dramatically.
Comment by: Rhonda Scholz
Sep 29, 2012 at 10:09 AM
I am purchasing a 22ft caravan with simplicity independent suspension. I have been given 2 options (1) 4" chassis with 3000kg suspension (2) 6" chassis with 3500kg suspension which is better and why Thanks
Comment by: John Beattie
Apr 20, 2012 at 2:32 PM
Thanks for the question, Basil! What you have said is pretty much on queue as a basic rule. BUT; ultimately all vans are different in their designs and interior layouts so this can shift the weight back and forth. To try and answer your question; You have to look at the whole picture, not just a mathematical calculation. With all the caravans and 5th wheelers i have designed over the years I look at the floor plan first and try to keep heavy items and larger storage areas close to the axles. This also goes for the chassis components, keeping water tanks and batteries etc at the axle. You should always keep more weight on the tow vehicle than in the rear of the van for stability. The ball weight should be kept within the legal capacity of the tow vehicle without being too light or too heavy.
Comment by: Basil Seldon
Apr 4, 2012 at 5:22 PM
A question came up whilst sitting around with afew caravaner friends. Is there a formula that calculates the location of the single independent suspenion so the correct weight on the tow ball is achived, eg length of the van sidewall divided by half with the wheel moved to the rear a certain distance? I've heard some say divide by half less 100mm and another said divide by half less the diameter of the wheel I hpoe you are able to answer this question. Regards Basil Seldon
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