Camper Trailer & Caravan Shock Absorbers with Fitting Position Front Axle, Rear Axle

A caravan or camper trailer needs shock absorbers for the same reason a vehicle does, and plenty of them either have none fitted or have a set that stopped working years ago.

Springs carry the weight and store energy as they compress. Without a shock to control the release of that energy, the trailer keeps moving after the bump has passed, and on a corrugated road that movement builds rather than settles.

Why Caravans and Camper Trailers Need Shock Absorbers

Small irregularities in the road surface set up vibration in the body of a trailer. With adequate damping, that vibration stops almost immediately. Without it, each input adds to the last and the trailer begins to bounce in a way that is genuinely dangerous at highway speed.

A bouncing trailer also loses tyre contact with the road, which affects braking on a trailer with electric or override brakes since the wheels need to be loaded to slow anything down. Vehicle sway becomes easier to provoke and harder to settle, because the trailer is moving independently of the tow vehicle rather than following it.

The other cost is everything the trailer carries. Cabinetry, appliances, fridges, water tanks and the chassis itself all absorb the loads a shock absorber would otherwise have controlled, which is why trailers without adequate damping develop cracks, loose fittings and broken contents on rough roads.

Fitting or upgrading shocks improves driving and braking stability, keeps the wheels in better contact with the ground, and protects what is inside.

How a Trailer Shock Absorber Works and Why It Fades

A shock absorber works by forcing oil through valves as the piston moves through the body. That restriction slows the movement of the spring and converts the energy into heat.

Heat is the problem on a corrugated road. As the oil warms it thins out and develops bubbles, a process known as aeration, and aerated oil cannot resist movement the way solid oil can. The result is shock fade, where damping falls away progressively and the trailer starts bouncing again despite the shocks being intact.

Manufacturers have several different ways of addressing fade. Gas pressurised designs use nitrogen to keep the oil under pressure so it resists aerating when worked hard. Twin tube designs circulate fluid between an inner and outer tube, which increases the oil volume and the surface area available to shed heat.

Foam cell construction takes the twin tube idea further, filling the space normally occupied by gas with a micro-cellular foam insert. Because the gas is held within the foam it cannot mix with the oil at all, and the insert takes up less room than a gas charge, which leaves space for more oil. More oil and no aeration means considerably longer before fade sets in.

Matching Shocks to Leaf, Coil or Independent Suspension

This is where most wrong purchases happen, and it is worth being blunt about it.

A shock absorber bought off the shelf as suiting a caravan is too general a description to be useful. Many are valved for coil spring suspension, and fitting one of those to a leaf sprung trailer will not control the springs properly because the two spring types behave differently.

Valving is described as a ratio between compression and rebound, and that ratio needs to suit the spring it is working against. A shock with the wrong balance either fails to control the spring or restricts the suspension so it never moves properly.

Australian trailers run leaf spring, independent coil, torsion bar and airbag setups, sometimes on the same chassis type from different model years. The suspension underneath dictates the shock, not the badge on the van.

If you are unsure what is fitted, a photograph of the suspension is more useful to us than the make and model of the van.

Shock Motion Ratio, Length and Mounting

Length is as important as valving and it is determined by geometry rather than preference.

Motion ratio is the relationship between how far the wheel travels and how far the shock travels. Because the shock usually mounts inboard of the wheel and at an angle, it moves less than the wheel does, and that ratio determines what open and closed lengths are correct.

Two limits have to be respected when choosing a length. The closed length must be shorter than the suspension's compressed position so the shock does not bottom out internally before the suspension does. The open length must be longer than whatever limits droop, whether that is a strap, a chain or the suspension itself, so the shock does not top out and take the load.

Get either wrong and the shock becomes a suspension stop, which destroys it and puts load through the mounts and the chassis.

Mounting angle matters alongside length, since most trailer shocks use rubber articulation eyes that tolerate a few degrees of angle without binding, and mounting outside that range wears the bushes quickly. A crush tube through the bush helps resist the side loading a trailer shock sees.

Matching the Shock to Trailer Weight

Trailer shocks are specified around a weight range, and a shock covering too wide a range damps poorly at both ends of it.

A shock designed to suit anything from a box trailer to a heavy touring van will be too firm for the light end and too soft for the heavy one. That is why quality ranges are divided into weight classes rather than sold as one universal item.

Work from the trailer's ATM and its actual loaded weight rather than its empty weight, since a van loaded for a trip can be considerably heavier than the tare figure suggests. Tandem axle trailers spread that load across four wheels rather than two, which changes what each shock is controlling.

Off Road Caravan and Camper Trailer Shocks

Corrugated dirt is the hardest condition a trailer shock will see, and it is where standard units fail.

The suspension cycles constantly rather than occasionally, so the oil never gets a chance to cool, and fade arrives sooner than it would on any sealed road. Off road rated shocks use larger bores, greater oil volume, foam cell or nitrogen construction, and heavier duty mounts and bushes to handle it.

Adjustable options exist for trailers as well, letting damping be firmed up when the van is loaded for a trip and softened when it is not.

Two shocks per side turn up on some heavier hybrid and off road vans, which spreads the work and the heat across more units. That is worth knowing if your van already has provision for it.

What Is in a Shock Absorber Upgrade Kit

A kit is the sensible purchase on a trailer that has never had shocks fitted, since the brackets are as important as the shocks themselves.

A typical kit supplies the pair of shock absorbers, top mounting brackets, bottom mounting brackets in left and right versions, and the mounting bolts and nuts. On leaf sprung trailers the bottom bracket often locates under the U-bolts using fish plates, and replacing the U-bolts at the same time is worth doing since they are single use by design once they have been stretched.

Replacement shocks on their own suit a trailer that already has brackets fitted and simply needs the dampers renewed.

Check whether the kit suits the spring width on your trailer, since the common sizes differ and a bracket built for one will not locate properly on the other.

Bleeding, Orientation and Clearance When Fitting Trailer Shocks

Bleed new shocks before mounting by extending and compressing them a few times in the vertical position, which settles the oil and gas correctly.

Orientation matters more than most people expect it to. Where the body and shaft differ in diameter, the larger body normally mounts uppermost, and most trailer installations angle the shock towards the rear of the trailer rather than mounting it vertically.

Weld-on brackets are used where the axle has no provision, bolt-on and plug-in brackets suit axles with existing mounting holes, and which applies depends entirely on the axle fitted.

Check clearance through the full range of suspension travel rather than at rest, including at full droop where a shock is most likely to be over-extended and at full compression where it can contact the chassis or the tyre.

Fulcrum has been working on suspension since 1976, with 16 Service Centres across Australia and 200+ authorised workshops. Matching shocks to the suspension actually fitted to your van, and mounting them at the correct length and angle, is what the network is there for.

Find Shock Absorbers for Your Caravan or Camper Trailer

Select your suspension type to see the caravan and camper trailer shock absorbers available for it, including replacement shocks and complete upgrade kits with brackets and hardware. Everything we supply is backed by our warranty, a fitment guarantee and the support of a nationwide workshop network.