Shock absorbers can be the most vulnerable part on your camper to wear and tear. They are also critical to the ease of towing a camper. The shock absorbers stabilise the ride of the camper in traditional road conditions. The serviceability varies depending on the road condition and most importantly the load on the camper and the speed of the vehicle. To put these factors in perspective, here is a simple chart:

Indicative Load Factor on Shock absorbers  for the purpose of illustrating the effect of speed and load
ATM= Aggregate Trailer Mass	Speed 80k/hr ATM 1250 kgs	Speed 100k/hr ATM 1250 kgs	Speed 80k/hr ATM 1600 kgs	Speed 100k/hr ATM 1600 kgs
30mm rise in Corrugations inconsistent centres	Factor 1	Factor 1.6	Factor 1.3	Factor 2.1
50mm rise in Corrugations at 300mm centres	Factor 2	Factor 3.2	Factor 2.6	Factor 4.2

Speed has a more dramatic effect on the serviceability of the shock absorbers than load does and the effect of speed is to the power of 2.

We have 2 types of shock absorbers in 2006 Models to meet the wide range of driving factors. To better explain the different types and selection, here is an overview on shock absorbers.

Overview

A shock absorber’s job is to primarily dampen the suspension, and keep the tires in contact with the road at all times. Modern designs have Nitrogen gas in them (an inert non-flammable gas, you breathe it everyday). The gas helps prevent and eliminate aeration, (the foaming and formation of bubbles inside), which causes the dampening ability of the unit to fade away. The better a unit's design can stop that from happening, the better performance and dampening ability it will tend to have.

Hydraulic Design

All shock absorbers are hydraulic in some way; they all have fluid inside them. But a pure Hydraulic shock would just have fluid and NO nitrogen gas inside. Most shocks made from the 1930's up to probably the 70's were of this design. Without Nitrogen gas inside, their dampening ability was extremely limited. Cavitation/aeration was a common problem, and any dampening ability the unit did have fades very quickly. This design is old and very few and made now.

Twin-tube Low Pressure Gas Design

This shock absorber is a low pressure gas, twin tube design. This basic design has been proven since the 1970’ and there have been some refinements over the years. This design has some characteristics, such as fixed valving, and usually costs less to manufacture than a Monotube or Adjustable type shock absorber. They are usually pressurized with some Nitrogen gas, usually 100 psi or less. In this design the hydraulic oil and gas are mixed together in the same chamber, which, while dampening, causes some heat, fading, and aeration/foaming. Under a high load factor, these shock absorbers will become very hot.

We tested both the Ridepro and Old Man Emu shocks for high temperature and found that only with the boat loader, boat and a well loaded camper that the temperature rose toward its limit (but within the limit).

The Ridepro Shocks we have selected have a 41mm bore and a 19mm shaft compared to the Old Man Emu with a 35mm bore and an 18mm shaft. The Ridepro carries 20% more capacity of fluid.

Mono-tube High Pressure Gas Design

This shock absorber is a high pressure, mono tube design. These are a newer design and the Monotube design allows them to operate at cooler temperatures. Monotube are under high pressure, from around 200 psi, to as high as 360 psi. The hydraulic oil and Nitrogen gas are in separate chambers, separated by a floating piston. This allows the shock/strut to function without any aeration or foaming. Monotube shocks usually have a stiff valving, and cost more to manufacture. They are also able to withstand more punishment, and offer higher dampening ability. Most racing shocks, including Formula One, are of a Monotube design. Accurate engineering is needed when manufacturing a Monotube, and many have a very specific valving. This is years of racing technology adapted for street and off-road use.

The Fox Monotube shocks that we have selected had NO Temperature rise during the test. They are smooth-bore seamless alloy body with Teflon lined steel aspherical bearings. These bearings won’t have the heat and deformation problems associated with polyurethane bushes under high camper loads. The shaft is hardened 17-4 stainless steel hard chromed. Billet Aluminium body caps/eyelets. It has clear cadmium body plating.

The Fox Mono-tube shock can be regassed. It can also be disassembled and any of the componentry replaced.

Photo of new Fox Monotube installed

Photos

Old Man Emu Shock Absorber N43

Fulcrum Shock Absorber

Ridepro Shock Absorber

Fox Monotube Shock Absorber