Suspension Glossary – Air Suspension, Springs, GVW Upgrades & Lift Kits Explained

This suspension glossary explains important terms related to suspension solutions for vehicles carrying heavy loads, operating with changing payloads or requiring improved stability and ride comfort.

Whether you own a motorhome, van, pickup, 4x4 vehicle, expedition vehicle or commercial vehicle, understanding suspension terminology can help you choose the right suspension upgrade for your needs.

This glossary covers auxiliary springs, heavy-duty replacement springs, semi air suspension systems, air suspension, full air suspension, GVW upgrades, lift kits, shock absorbers and many other commonly used suspension terms.

Table of Contents

Auxiliary Springs, Reinforced Springs & Helper Springs

Auxiliary springs are commonly referred to as reinforced springs, helper springs, heavy-duty springs or aftermarket springs. These suspension solutions are designed to support, reinforce or replace the original suspension when a vehicle regularly carries heavy loads.

They are widely used on motorhomes, vans, pickups, 4x4 vehicles, expedition vehicles, service vehicles and commercial vehicles operating with high payloads.

Auxiliary Spring

An auxiliary spring is installed in addition to the original suspension spring and supports the factory suspension under load. It helps improve load carrying capacity, ride stability and vehicle control when carrying heavy payloads.

Auxiliary springs are commonly used on vehicles that regularly transport tools, equipment, cargo, camper conversions or other heavy loads.

Auxiliary Springs

Auxiliary springs work alongside the original suspension system and provide additional support when vehicle weight increases. They help reduce rear-end sag and maintain a more level ride height.

Reinforced Spring

A reinforced spring is a general term for a suspension spring with increased load capacity. Reinforced springs are designed to improve stability and support vehicles operating under demanding load conditions.

Heavy-Duty Replacement Spring

A heavy-duty replacement spring completely replaces the original suspension spring. It provides greater load capacity than the factory spring and is intended for vehicles that frequently operate with high payloads.

Heavy-duty replacement springs are commonly fitted to vans, pickups, motorhomes and commercial vehicles.

Helper Spring

A helper spring is often used as another name for an auxiliary spring. It assists the main suspension spring when vehicle load increases and helps maintain ride height and stability.

Heavy-Duty Spring

A heavy-duty spring is specifically designed for continuous operation under high loads. It provides increased support and durability compared with standard suspension springs.

Heavy-duty springs are commonly used on commercial vehicles, motorhomes, pickups and expedition vehicles.

Load Support Spring

A load support spring is designed to increase the load-carrying ability of a vehicle and reduce suspension sag when transporting heavy cargo.

These springs help improve vehicle balance and handling when operating near maximum payload capacity.

Aftermarket Spring

An aftermarket spring is installed after the vehicle has left the factory to improve load capacity, suspension performance, ride quality or vehicle stability.

Aftermarket springs are frequently used when the original suspension is no longer suitable for the vehicle's intended use.

Progressive Spring

A progressive spring changes its spring rate depending on the amount of load applied. Under light loads it provides a comfortable ride, while under heavier loads it offers increased support and stability.

Progressive springs are commonly used on vehicles that operate both unloaded and heavily loaded.

Spring Rate

The spring rate describes the relationship between applied load and spring compression. It plays a major role in determining ride comfort, handling characteristics and load-carrying performance.

Suspension Upgrade

A suspension upgrade includes modifications designed to improve ride quality, vehicle stability, payload handling or off-road performance.

Examples include auxiliary springs, heavy-duty replacement springs, auxiliary air springs, full air suspension systems and upgraded shock absorbers.

Semi Air Suspension, Air Suspension & Full Air Suspension

Air suspension systems are among the most popular suspension upgrades for vehicles carrying varying loads. They are widely used on motorhomes, vans, pickups, 4x4 vehicles and commercial vehicles to improve ride comfort, vehicle stability and load handling.

Depending on the application, air suspension systems can either support the existing steel suspension or completely replace it.

Semi Air Suspension

Semi Air Suspension is a suspension system that combines the original steel suspension with auxiliary air springs. The air springs support the existing leaf springs or coil springs but do not replace them.

By adjusting the air pressure, the suspension can be adapted to different load conditions. Semi Air Suspension systems help improve vehicle stability, reduce rear-end sag and increase ride comfort when carrying heavy loads.

Semi Air Suspension is commonly used on motorhomes, vans, pickups and commercial vehicles with varying payloads.

Auxiliary Air Spring

An Auxiliary Air Spring, often referred to as a Semi Air Suspension system, supports the existing leaf spring or coil spring suspension of a vehicle.

Air bellows carry part of the load and relieve stress on the original suspension. The air pressure can be adjusted to suit changing payload conditions.

Auxiliary Air Springs

Auxiliary Air Springs are designed to work together with the factory suspension. They help maintain vehicle height, improve stability and reduce suspension sag under load.

They are commonly fitted to motorhomes, camper vans, pickups, service vehicles and commercial vehicles.

Air Helper Springs

Air Helper Springs are another common term for auxiliary air springs used in Semi Air Suspension systems. They support the original suspension and help maintain ride height and vehicle stability under heavy loads.

Air Assisted Suspension

Air Assisted Suspension refers to a suspension system where air springs assist the original steel suspension. The factory suspension remains in place while the air springs provide additional load support and ride height control.

Auxiliary Air Suspension

Auxiliary Air Suspension is another commonly used term for air suspension systems that supplement the original suspension rather than replacing it completely.

These systems are particularly popular on vehicles that regularly operate with changing payloads.

Air Suspension

Air Suspension uses compressed air as the suspension medium instead of relying solely on conventional steel springs.

By varying air pressure, the suspension characteristics can be adjusted to match vehicle load and driving conditions.

Air Spring

An Air Spring is the actual spring element used within an air suspension system. It is usually made from reinforced rubber and filled with compressed air.

Depending on the system design, air springs may support part or all of the vehicle load.

Air Bellows

An Air Bellows is the flexible rubber component that contains compressed air inside an air suspension system.

Air bellows are responsible for generating the spring effect and supporting the vehicle load.

Full Air Suspension

With Full Air Suspension, the original steel springs are completely replaced by air springs. The air suspension system takes over the entire spring function of the vehicle.

By automatically adjusting air pressure, vehicle height remains constant regardless of payload. Full Air Suspension provides excellent ride comfort, improved driving stability and advanced levelling capabilities.

Retrofit Full Air Suspension systems are available for selected motorhomes, vans, pickups and 4x4 vehicles.

Self-Levelling System

A Self-Levelling System automatically maintains a predefined vehicle height regardless of load distribution or payload.

This helps improve driving stability and vehicle handling under changing operating conditions.

Ride Height Adjustment

Ride Height Adjustment allows the vehicle height to be raised or lowered depending on operating requirements.

This feature is commonly found on advanced air suspension systems and Full Air Suspension conversions.

Air Suspension Chassis

An Air Suspension Chassis is a suspension system where air springs perform a significant portion or all of the suspension function.

Air suspension chassis systems are valued for their comfort, stability and adaptability.

Single-Circuit Air Suspension

With a Single-Circuit Air Suspension system, both air springs are connected and inflated together.

This design is simple and cost-effective and is commonly used where load distribution is relatively even.

Dual-Circuit Air Suspension

With a Dual-Circuit Air Suspension system, the left and right air springs can be adjusted independently.

This allows uneven loads to be compensated more effectively and improves vehicle levelling capabilities.

GVW Upgrades, Axle Loads & Payload

Motorhomes, vans, pickups and commercial vehicles often reach the limits of their permitted vehicle weight when carrying passengers, equipment, tools, cargo or camper conversions. Understanding weight-related terms is essential when considering suspension upgrades or a GVW upgrade.

The following terms explain the most important concepts related to vehicle weights, payload capacity and axle load limits.

GVW Upgrade

A GVW Upgrade increases the legally permitted Gross Vehicle Weight (GVW) of a vehicle. This allows the vehicle to carry more weight than originally approved by the manufacturer.

Depending on the vehicle, a GVW Upgrade may require upgraded suspension components, technical documentation and official approval.

GVW Upgrade Approval

A GVW Upgrade Approval is the technical documentation required to support an increase in the permitted Gross Vehicle Weight of a vehicle.

This approval forms the basis for inspection, certification and registration of the upgraded vehicle weight.

Gross Vehicle Weight (GVW)

Gross Vehicle Weight (GVW) is the maximum legally permitted operating weight of a vehicle.

It includes the vehicle itself, driver, passengers, fuel, water, luggage, accessories and cargo.

Gross Vehicle Weight Rating (GVWR)

Gross Vehicle Weight Rating (GVWR) is the manufacturer's specified maximum permitted vehicle weight.

Operating a vehicle above its GVWR may affect safety, legality and vehicle performance.

Payload

Payload is the amount of weight that can be added to a vehicle once it is ready for operation.

Payload includes passengers, luggage, tools, camping equipment, water tanks, bicycles, cargo and other carried items.

Payload Capacity

Payload Capacity describes the maximum allowable payload that can be carried while remaining within legal weight limits.

Increasing payload capacity is one of the main reasons for suspension upgrades and GVW Upgrades.

Payload Upgrade

A Payload Upgrade increases the amount of weight a vehicle can legally carry. In many cases, this is achieved through a GVW Upgrade combined with suitable suspension modifications.

Axle Load

Axle Load is the amount of weight carried by an individual axle of the vehicle.

Front and rear axles each have their own maximum permitted load limits that must not be exceeded.

Axle Load Upgrade

An Axle Load Upgrade increases the permitted load capacity of a specific axle.

This is particularly useful when one axle reaches its limit before the overall vehicle weight limit is reached.

Rear Axle Upgrade

A Rear Axle Upgrade increases the permitted load on the rear axle.

Rear axle upgrades are especially common on motorhomes, vans and pickups where significant weight is carried behind the vehicle's centre line.

Rear Axle Load

Rear Axle Load refers to the actual weight carried by the rear axle.

Motorhomes, service vehicles and pickups often operate with high rear axle loads due to equipment, cargo or camper conversions.

Front Axle Load

Front Axle Load refers to the actual weight carried by the front axle.

Additional accessories such as winches, bull bars, heavy bumpers or front-mounted equipment can increase front axle load.

Kerb Weight

Kerb Weight is the weight of a vehicle in standard operating condition as specified by the manufacturer.

Definitions may vary slightly depending on local regulations and manufacturer standards.

Vehicle Weight

Vehicle Weight refers to the actual weight of a vehicle at any given time.

It changes depending on passengers, fuel, water, cargo, equipment and accessories carried.

Weight Reserve

Weight Reserve is the difference between the actual vehicle weight and the permitted Gross Vehicle Weight.

A larger weight reserve provides more flexibility for carrying passengers, luggage and equipment.

Overloading

Overloading occurs when the actual vehicle weight or an axle load exceeds the legally permitted limit.

Overloading may negatively affect braking performance, handling, tyre wear and vehicle safety.

Suspension Reinforcement

Suspension Reinforcement refers to modifications intended to improve vehicle load-carrying ability and stability.

Examples include auxiliary springs, heavy-duty replacement springs, auxiliary air suspension systems and upgraded shock absorbers.

Lift Kits, Suspension Lifts & Ground Clearance

Lift kits are among the most popular suspension upgrades for pickups, 4x4 vehicles, off-road vehicles, expedition vehicles and adventure vans. They can improve ground clearance, allow the installation of larger tyres and enhance off-road capability.

Depending on the vehicle and intended use, lift kits may include springs, spacers, shock absorbers or complete suspension systems.

Lift Kit

A Lift Kit is a suspension upgrade designed to raise the height of a vehicle above its factory ride height.

Lift kits are commonly used to improve off-road capability, increase ground clearance and accommodate larger tyres.

Suspension Lift

A Suspension Lift raises a vehicle through modifications to the suspension system itself.

This may include longer springs, upgraded suspension components, spacers or complete suspension assemblies.

Suspension Lift Kit

A Suspension Lift Kit is a complete package containing the components required to raise a vehicle through suspension modifications.

Depending on the vehicle, the kit may include springs, spacers, brackets, shock absorbers and installation hardware.

Body Lift

A Body Lift raises the vehicle body relative to the chassis or frame.

Unlike a Suspension Lift, a Body Lift does not significantly change suspension geometry and is most commonly used on body-on-frame vehicles.

Levelling Kit

A Levelling Kit is designed to raise either the front or rear of a vehicle in order to achieve a more level stance.

Levelling kits are particularly popular on pickups where the rear of the vehicle sits higher than the front when unloaded.

Ground Clearance

Ground Clearance is the distance between the lowest point of the vehicle and the ground.

Increasing ground clearance can help a vehicle clear obstacles more easily and reduce the risk of underbody contact.

Off-Road Suspension

An Off-Road Suspension system is specifically designed for driving on rough terrain, gravel roads, trails and challenging off-road conditions.

It may include upgraded springs, shock absorbers and other components designed to withstand demanding environments.

Suspension Travel

Suspension Travel describes the total movement range of the suspension between full compression and full extension.

Adequate suspension travel is important for ride comfort, wheel traction and off-road performance.

Axle Articulation

Axle Articulation describes the ability of a suspension system to allow the wheels to move independently when travelling over uneven terrain.

Improved axle articulation helps maintain traction and vehicle control in off-road situations.

Breakover Angle

The Breakover Angle describes the maximum angle a vehicle can pass over without the underside contacting the ground.

Higher vehicles generally benefit from improved breakover angles.

Approach Angle

The Approach Angle is the maximum angle of an obstacle that can be approached from the front without the vehicle touching the ground.

This measurement is particularly important for off-road vehicles.

Departure Angle

The Departure Angle is the maximum angle a vehicle can descend or leave an obstacle without the rear of the vehicle contacting the ground.

Larger Tyres

Many vehicle owners combine a Lift Kit with larger tyres.

Larger tyres can further increase ground clearance and improve off-road capability.

Ride Height

Ride Height refers to the distance between the vehicle chassis and the ground.

Changes in ride height influence ground clearance, vehicle appearance and off-road performance.

Lift Kit Approval

Depending on the vehicle, country and lift system used, technical inspection, certification or registration may be required.

Vehicle owners should always ensure that modifications comply with local regulations.

Shock Absorbers, Springs & Suspension

Shock absorbers, springs and suspension components play a major role in vehicle comfort, stability and safety. They help keep the tyres in contact with the road, improve handling and ensure predictable vehicle behaviour under different driving conditions.

Whether a vehicle is used for daily driving, commercial work, heavy payloads or off-road travel, a properly functioning suspension system is essential.

Suspension

Suspension refers to the collection of components that connect the vehicle to the road surface.

These components include springs, shock absorbers, control arms, axles, wheels and other suspension-related parts.

Suspension System

A Suspension System is designed to absorb road irregularities, improve ride comfort and maintain tyre contact with the road.

The suspension system plays a key role in handling, braking performance and vehicle stability.

Suspension Spring

A Suspension Spring supports the weight of the vehicle and absorbs vertical movement caused by bumps and uneven road surfaces.

Different spring types are used depending on vehicle design and intended use.

Coil Spring

A Coil Spring is one of the most common suspension spring designs used on passenger cars, SUVs, pickups and many vans.

Coil springs provide a good balance between ride comfort, handling and load-carrying capability.

Leaf Spring

A Leaf Spring consists of multiple layers of spring steel stacked together.

Leaf springs are widely used on pickups, commercial vehicles, trailers and vehicles designed for high payload capacity.

Shock Absorber

A Shock Absorber controls the movement of the suspension spring and prevents excessive bouncing after bumps or road irregularities.

Without shock absorbers, a vehicle would continue to oscillate after every suspension movement.

Gas Pressure Shock Absorber

A Gas Pressure Shock Absorber uses pressurised gas to improve damping response and reduce fade during demanding driving conditions.

These shock absorbers are commonly used to improve handling and stability.

Heavy-Duty Shock Absorber

A Heavy-Duty Shock Absorber is designed for vehicles operating under increased loads or demanding conditions.

They are commonly fitted to motorhomes, vans, pickups, expedition vehicles and commercial vehicles.

Driving Stability

Driving Stability describes how well a vehicle maintains control during cornering, braking, acceleration and adverse weather conditions.

Proper suspension tuning contributes significantly to overall vehicle stability.

Body Roll

Body Roll refers to the sideways leaning movement of the vehicle body when cornering.

Suspension upgrades, auxiliary springs and air suspension systems can help reduce excessive body roll.

Pitching

Pitching describes the forward and backward movement of the vehicle body during braking or acceleration.

A well-balanced suspension system helps minimise excessive pitching.

Side Wind Sensitivity

Side Wind Sensitivity describes how strongly a vehicle reacts to crosswinds.

Tall vehicles such as motorhomes, camper vans and high-roof vans often benefit from suspension improvements that increase stability.

Bottoming Out

Bottoming Out occurs when the suspension reaches the end of its available travel and can no longer absorb additional impacts.

This can occur when a vehicle is overloaded or when suspension components are no longer suitable for the operating conditions.

Suspension Travel

Suspension Travel describes the distance a suspension system can move between full compression and full extension.

Adequate suspension travel contributes to comfort, traction and vehicle control.

Progressive Spring

A Progressive Spring changes its spring rate as load increases.

It provides a comfortable ride under light loads while offering increased support when carrying heavier loads.

Spring Rate

Spring Rate describes the relationship between load and spring compression.

It has a major influence on ride quality, handling and load-carrying performance.

Ride Comfort

Ride Comfort refers to how effectively the suspension system isolates vehicle occupants from bumps and road imperfections.

Springs, shock absorbers and overall suspension design all contribute to ride comfort.

Suspension Upgrade

A Suspension Upgrade includes modifications intended to improve ride quality, driving stability, load handling or off-road performance.

Examples include auxiliary springs, heavy-duty replacement springs, auxiliary air suspension systems, full air suspension systems, upgraded shock absorbers and lift kits.

Frequently Asked Questions About Suspension Terms

What is the difference between an Auxiliary Spring and an Auxiliary Air Spring?

An Auxiliary Spring is a mechanical steel spring that supports the existing suspension. An Auxiliary Air Spring uses compressed air and can be adjusted to suit different load conditions.

Does an Auxiliary Air Spring automatically increase legal payload?

No. An Auxiliary Air Spring improves stability and supports the suspension. A legal increase in payload requires an approved GVW Upgrade and the necessary certification.

When is a Suspension Upgrade recommended?

A Suspension Upgrade is recommended when a vehicle regularly carries heavy loads, operates with changing payloads or requires improved ride quality and stability.

What is the difference between Semi Air Suspension and Full Air Suspension?

Semi Air Suspension supports the existing steel suspension using auxiliary air springs. Full Air Suspension completely replaces the original steel springs and performs the entire suspension function.

Which vehicles benefit most from suspension upgrades?

Motorhomes, vans, pickups, 4x4 vehicles, expedition vehicles, service vehicles and commercial vehicles often benefit from suspension upgrades, especially when operating with heavy or changing payloads.