Caravan Shock Absorbers

One of the questions I often get asked is whether it’s worth fitting shock absorbers to a caravan. Before looking at the pros and cons we need to understand a little about how the suspension on a modern caravan works. To save space and weight the springs and shock absorbers found in more conventional systems are replaced by an axle tube containing long strips of rubber that deform under load. The construction is such that there is some resistance to movement and this provides a degree of shock absorption. To see it in action click here.

Whilst the arrangement provides an excellent overall compromise between weight and space on the one hand and performance on the other, the shock absorbing properties are not as good as they would be if dedicated shock absorbers were fitted. The question is ‘does this matter?’

The answer depends on your point of view and where you want to use your caravan. In normal driving on good UK roads the answer is probably not. However on poorer roads, such as some of those found in Eire, it’s a different matter. Also if you want to tow at 100kph on German roads then shock absorbers are a legal requirement (one of several). This could explain why most continental vans are fitted with shock absorbers as standard.

The benefits of shock absorbers go beyond reducing the vibration of the van and its contents. By controlling the movement between the body of the van and its wheels the van becomes more stable to tow and is less affected by passing lorries and coaches. Also, when braking on uneven surfaces, shock absorbers will help to keep the wheels in firm contact with the road thereby reducing stopping distances.

Most UK caravans, including those produced by the Swift Group, are built on chassis from the German manufacturer AL-KO Kober. The suspension systems contain 3 strips of rubber compressed in a six sided cross section tube. However caravans produced by the Explorer Group come on chassis from another German manufacturer - BPW. The suspension systems on these use 4 strips of rubber, an arrangement that is claimed to be less in need of shock absorbers than those with 3 strips. Nevertheless some owners report improved towing after fitting them. Beware that not all BPW chassis have mounting points for shock absorbers.

I remember the first outing after fitting shock absorbers to my caravan. The beginning of the journey was slow, in heavy traffic but then we got on a relatively empty dual carriageway so I put my foot down to make up for lost time. Then, with the speedo on 60mph, I saw a big rut right in front of me and right across the road. It was the remains of a trench that had been filled and then sunk. There was nothing I could do except brace myself for the reaction that was surely to come via the tow hitch. Amazingly there was virtually none. Also when we got to site the fire front was still in place for the first time in many outings

Left: The kit for one axle

Right: the two halves of the mounting bracket have been inserted 'back to back' and will shortly be squeezed together using a 'G' clamp

If you do decide to fit shock absorbers to your Swift Group caravan it’s a very easy process as the suspension and chassis are already designed to take them. Alko supply shock absorbers of 3 ratings according the weight of the caravan to which they will be fitted. For easy identification each rating has its own colour as follows:

AL-KO Part No.	Colour Code	Axle weights (GVW)
601204	Green	Single Axles Tandem Axles	Up to 900 kg Up to 1600 kg
601205	Blue	Single Axles Tandem Axles	901 - 1300 kg 1601 - 2600 kg
601206	Red	Single Axles Tandem Axles	1301 - 1800 kg 2501 - 3500 kg

Please note that tandem axle vans require 2 sets, i.e. 4 shock absorbers in total.

Fitting requires the removal of each wheel in turn (follow normal precautions for this). Next a rubber plug needs to be removed from the underside of the radius arm. This allows the insertion of the two halves of the new arm to which one end of the shock absorber will fit. The two halves must be inserted individually then squeezed together so they open up in the radius arm and grip it tightly. The instructions say use pliers for this but I needed a ‘G’ clamp. The other end of the shock absorber bolts to an existing hole in the chassis, the exact hole being determined according to a table in the fitting instructions.

The only thing to beware of is that where a motor mover has been fitted to chassis of the van there may be insufficient clearance for the shock absorbers. Sometimes the motor mover can be adjusted to overcome this but it may be worth checking with the mover manufacturer to see if they have tested the mover on a van fitted with shock absorbers.

This caravan mover has been designed to accommodate shock absorbers and transfers the power to the roller via a chain to save space.

The dark patch on the sets is water that ran out out the radius arm when the plug for the hole where the shock absorber bracket fits was removed. The inside of the arm was treated with Waxoyl before the bracket was fitted.

Footnote
From September 2008 all Swift and Sterling brand caravans now come with shock absorbers as standard 'for a smoother more stable ride'. That says it all really. Bailey also fits them to all of its caravans except some entry level Ranger models.