How to Inflate Air Helpers and Determine the Correct Pressure
Correct inflation is one of the most neglected and misunderstood aspects of air-helper maintenance—yet it is probably the most important.
Operating air helpers, also commonly called suspension airbags, while underinflated or overinflated can drastically reduce their lifespan and may damage them. Fortunately, determining the correct pressure is relatively simple when the correct method is followed.
Minimum Pressure Is Not Always the Correct Pressure
Most air-helper suppliers specify a minimum and maximum pressure—for example, a minimum of 0.3 bar and a maximum of 7 bar.
These figures are operating limits, not necessarily the correct pressures for every vehicle and load.
The maximum pressure must never be exceeded. However, the specified minimum pressure may be insufficient to maintain the air helpers at their correct operating height.
The correct pressure cannot be determined from pressure alone. It must be determined by measuring the installed height of the air helpers.
Why Vehicles Require Different Pressures
Air helpers are installed between the vehicle’s chassis and rear axle using upper and lower steel mounting brackets. A correctly designed system positions the air helpers within the available space using brackets designed specifically for that vehicle.
Two main factors can reduce the distance between the chassis and axle and compress the air helpers.
Permanent or Additional Load
Do not underestimate the weight permanently carried by a vehicle. A canopy, drawer system, replacement bumper, long-range fuel tank, tools and recovery equipment can add considerable weight—even when the vehicle appears to be unloaded.
This additional weight compresses the original suspension and lowers the rear of the vehicle.
The position of the load is also important. Weight positioned far behind the rear axle can have a greater effect on rear suspension height than the same weight positioned directly over or ahead of the axle.
Worn or Sagging Springs
Coil springs and leaf springs settle as they age, particularly on vehicles that have travelled high kilometers or regularly carried heavy loads.
Sagging springs reduce the original distance between the chassis and axle. In this situation, the air helpers may require considerably more than 0.3 bar to maintain their correct operating height.
What Is the Correct Air-Helper Height?
For applicable AmadaXtreme systems, the air helpers should have an installed height of approximately 150 mm when the vehicle is parked on level ground.
This measurement is taken across the complete air helper, from the outer surface of the upper steel ring to the outer surface of the lower steel ring. Do not include the vehicle-specific mounting brackets attached to the chassis and axle.
The pressure required to maintain this 150 mm height will differ between vehicles according to:
- The vehicle’s permanent load
- The position of the load
- The condition of its coil or leaf springs
- Additional cargo
- Trailer or caravan nose weight
This is why one fixed pressure cannot be recommended for every vehicle.
How to Establish the Correct Unloaded Pressure
It is easier to perform this procedure with someone assisting you.
- Park the vehicle on a firm, level surface.
- Inflate the air helpers gradually until the rear of the vehicle sits noticeably higher. Approximately 3–4 bar may be sufficient, depending on the vehicle and load. Never exceed the system’s maximum permitted pressure.
- Measure the vertical distance across the complete air helper, from the upper steel ring to the lower steel ring.
- Ask your assistant to release the air slowly while you monitor the measurement.
- Stop releasing air when the air-helper height reaches approximately 150 mm.
- Check the pressure and record it.
This is the correct starting pressure for that particular vehicle in its current load condition. It may be higher than the supplier’s stated minimum pressure, especially when the vehicle carries permanent equipment or has settled springs.
Safety warning: The vehicle must remain standing on its wheels while taking this measurement. Ensure there is sufficient clearance beneath the vehicle, as the rear will lower while an assistant slowly releases the air pressure.
Establishing a Reference Height
Once the air helpers have been adjusted to the correct 150 mm operating height, choose a fixed and easily repeatable measuring point at the rear of the vehicle. A specific point on the towbar usually works well.
Measure vertically from this exact point to the ground and record the measurement.
This becomes the vehicle’s reference height. For consistent measurements, always use:
- The same point on the towbar
- A firm, level surface
- Correct tyre pressures
- The vehicle’s normal permanent equipment
Recording this reference height makes future adjustments much easier because you will not need to measure the air helpers underneath the vehicle every time the load changes.
Adjusting the Pressure When Loaded or Towing
When cargo or trailer nose weight is added, the rear of the vehicle will lower.
Inflate the air helpers gradually until the previously recorded towbar measurement is restored. Then check and record the pressure.
This is the correct pressure for that specific load. If the cargo, load position or trailer nose weight changes, the required pressure may need to be adjusted again.
The correct pressure is not necessarily the highest pressure. Inflating the system beyond the amount required to restore the reference height can make the rear suspension unnecessarily firm and may overextend the air helpers.
Height Determines the Correct Pressure
A pressure gauge is a useful reference, but pressure alone cannot tell you whether the air helpers are correctly inflated.
Every vehicle is different. Two identical vehicles may require different pressures because of their permanent equipment, load position and spring condition.
The correct procedure is therefore:
- Establish the correct 150 mm air-helper operating height.
- Record the corresponding towbar reference height.
- Inflate the system to restore that height whenever the load changes.
- Record the pressure required for frequently carried loads or regular towing conditions.
In short, determine the correct height first and then record the pressure required to maintain it.