When it comes to an off-road caravan's suspension there is a big gap between "bells and whistles" and "core essentials". Start by looking underneath to see the big differences.
The image on the left shows the contrast of suspension (and braking) systems.
Conveniently they are completely colour coded red and blue! Lets look at the 2 contrasting systems. The Blue system is by Kimberley and fitted to an off road caravan with a tare weight of 2.7 tonnes. The red system is from another manufacturer with a plated "axle load" of 3.49 tonnes.
The Suspension system comprises the wheel (and tyre), the brake hub, the suspension arm, the spring and the shock absorber. In some units there is an anti-sway bar (visible in the blue system).
Lets start with the brakes.
The red suspension system shows the drum brakes with electric activiation. These are the bigger "12inch" drum brakes and there is an "off road" protection plate added to the inside.
The photo on the right is a close-up of the red suspension. It shows the electric activation wire from the magnet/ drum brake assembly (white) coming out of the back of the drum brake. It is "joined' to a black activation wire that runs to the trailer plug. The join is surrounded by black electrical tape and it is held in position with the cable tie.
Drum brakes have these disadvantages:
- They fade
- They perform poorly when wet
- They are heavy and add to the "unsprung weight"
- They require regular maintenance
- They reply on an electrical wire for activation
- And the most difficult issue: The hand brake is a mechanical level that requires quite some presure.
Drum bakes have these advantages:
- They are easy to add to install
- They are low cost
The Blue image shows the Disc Brakes which have:
- Less than half the weight of the drum brakes
- More than twice the stopping performance.
- Easy to change a disc pad
- No fading and fast recovery when wet
- And a big issue: The parking brake is a one touch operation that locks the 4 disc brakes solid as a parking brake.
Then we examine the spring and shock absorber.
The red system has coil springs and a reputable brand of Twin tube shock absorber. There is a separate blog on the remarkable differences between twin tube and the mono-tube shock absorbers
in the blue Kimberley system on the right.
||Red System Coil/ Twin Tube Shock
||Blue System Air spring/Mono-tube shock
|Travel (up and down vertically)
||A very short travel system
||Approximately twice the travel distance as measured.
| Performance in high heat generation when travelling over corrugations
||The heat is disipated in the shock absorber which needs maximum air flow. Any obstruction like the springs and cups in the red system will deteriorate performance.
||The shock absorber has a free and clear air for maximum heat disipation.
| When camping off road
||To change the caravan level, wheel ramps and chocks are required.
||To change the caravan level, simply adjust each air bag with a finger controlled valve until level.
| Variable rate for the big bumps?
|| No, fixed spring rate
|| Yes, variable spring rate with increase at bottom of compression stroke
Then finally the chassis and anti-sway system
||Hot dipped galvanized which provides best protection inside the RHS sections which sre NOT visible on outside
||Anti-sway bars are added for safety stability with the air suspension in the unlikely effent the air bag ruptures or leaks when cornering
These are the individual components. When they all go together, the entire system has 2 very important factors for off road use:
- The travel height of the suspension has to be both high but also to have greater suspension travel than traditional caravans
- The unsprung weight of the suspension has to be the absolute lowest possible. This is a determining factor in caravan stability.
To read more on this subject consider these blogs or eBooks: