Which air suspension is right for my motorhome – 150/2 or 170/2?

Definition of the 170/2 and 150/2 air springs

The terms ‘150/2’ and ‘170/2’ refer to the size of the air springs used for motorhomes and vans. The first symbol means diameter of the bellow, and the second is information, how many parts bellow is divided.

• 150: These 150 mm air springs are used on lighter vehicles or those with a gross vehicle weight rating (GVWR) of up to 4 tonnes. They usually have triple bellows (150/3) and offer a moderate suspension that is enough for less loaded vehicles.
• 170: These 170 mm air springs are suitable for heavier vehicles with a gross vehicle weight over 4 tonnes. They have a double bellows that can absorb a larger amount of air, which ensures a higher load capacity and stability. They are therefore especially recommended for vehicles with a high weight or large overhang.

How to choose the right air suspension?

Some air suspension manufacturers recommend only one size of air bellows for certain base vehicles, which is not always the best solution.

1. Base vehicle and installation space for air springs:

The installation situation will determine whether a 150 or 170 mm air bellows will fit. In some vehicles, especially those with stabilisers or other installations, space is limited so that larger air springs will not fit. As a rule, the air bellows replace the original bump stops. In some vehicles, it can be difficult to fit 170 mm air bellows due to lack of space, as they are often twice the diameter of bump stops.

2. Comfort and pressure conditions

The air pressure and the size of the air bellows have a significant impact on the riding experience:

• Lower pressure in the air bellows provides more suspension comfort.
• Larger air bellows distribute the pressure better over the surface and are therefore softer under the same load. This means that less compression is required for the same load, which makes the suspension more comfortable.

3. Total weight and planned load increase:

Retrofitting air springs not only serves to increase comfort and safety, but also to increase the maximum load on the vehicle. The selection of the correct air suspensions bellows size depends on the type approval and the V5C. If you are planning to increase the load, it is advisable to choose an air suspension that is designed for this load.

4. Overhang and rear axle load

Although the air bellows are tested for higher loads than they are authorised for, the maximum permitted load should not be exceeded. Particularly in long motorhomes with a large overhang, the load distribution on the front and rear axles is not equal, which should be taken into consideration when selecting the air suspension for motorhome, van or other vehicle.

The maximum axle loads can be found in the cars manual or on its attached plate. The maximum load of the air bellows should not exceed these values in order to ensure safety and stability.

Golden rules for selecting air springs

• 170 mm air springs are generally more suitable for vehicles with a gross vehicle weight of over 3.5 tonnes.
• For motorhomes with an overhang of more than 2 metres, 170/2 or 170/3 air springs are also recommended to ensure sufficient stability.
• Observe the air spring manufacturer's specifications regarding the load increase and the permitted loads.

Air suspension bellows: choose the correct one for your vehicle!

The choice between 150/2 and 170/2 air springs depends on various factors, such as the weight of the vehicle, the available installation space and the desired ride comfort. Lighter motorhomes usually benefit from the more compact 150/2 or 150/3 air springs, while heavier vehicles are often better equipped with 170/2 or 170/3 air springs due to their higher load capacity and stability. However, it is important to note that not all manufacturers offer both sizes for every vehicle, even if larger air springs could technically be fitted.

At X-CAMPING you will find a large selection of air suspension systems from various manufacturers. XIMPLIO offers both variants where technically possible, while LEMET specialises exclusively in the more durable 170 air springs.

When making your decision, you should also take into account possible future load increases and the individual circumstances of your vehicle. This is the only way to ensure that your motorhome is always optimally sprung and safe on the road.

Note: Although the article shows photos of the installation of additional air suspension on the Fiat Ducato, this guide is universal and applies to a wide range of vehicles. These include models such as the Ford Transit, Opel Movano, Renault Master, Mercedes Sprinter, Fiat Ducato (230, 244, 250 series), Peugeot Boxer, Citroen Jumper, Iveco and many more. The instructions are suitable for vehicles with both single and twin tyres, as well as for Euro chassis and vehicles with front or rear-wheel drive. No matter which vehicle you drive - the basic principles for selecting and fitting the right air suspension remain the same and can be adapted to the specific requirements of your vehicle.