Publish Time: 2025-05-15 Origin: Site
Lift axles, including steerable axles, are essential components in heavy-duty trucking, enabling operators to increase payload capacity, improve weight distribution, and comply with varying regulatory requirements. However, specifying and installing lift axles-especially steerable lift axles that can follow the path of least resistance-requires careful engineering and planning. This article explores key considerations for selecting lift axles, compares lift axle systems with liftable suspensions, and highlights the benefits and challenges of retrofitting steerable lift axles, with a focus on solutions provided by LUEN, a leading manufacturer of trailer and truck axles and suspension systems.
A lift axle is an auxiliary axle, often referred to as a tag axle, that can be raised or lowered as needed. When lowered, it provides an additional load-bearing point, allowing trucks to legally carry heavier payloads by distributing weight over a certain number of axles. When raised, it reduces tire wear and rolling resistance during lighter loads or empty runs.
In contrast, a liftable suspension adjusts the height of the suspension system but does not add an extra axle. This system improves ground clearance and ride quality but does not increase the truck's legal weight capacity.
When deciding between lift axle vs liftable suspension, operators must consider their specific needs. Lift axles provide increased payload capacity and regulatory compliance benefits, while liftable suspensions offer flexibility in ride height and terrain clearance without the complexity of an additional axle.
LUEN offers a range of American type air suspensions with lift capabilities, designed to integrate seamlessly with their lift axle products, providing operators with versatile options tailored to their operational requirements.
Axle weight limits and spacing are governed by a patchwork of federal, state, and local regulations due to the ever-changing bridge laws in Canada. While federal bridge formulas set baseline standards for interstate travel, many states impose unique axle weight limits and spacing requirements. This variability means that a truck lift axle configuration legal in one state may not be permissible in another.
Operators who frequently cross state lines must often compromise on axle spacing and weight to comply with the strictest jurisdictions on their routes. Consulting with local dealers and upfitters familiar with regional regulations is essential to ensure compliance and avoid costly fines.
LUEN's extensive experience in international markets, including Africa, South America, and the Middle East, equips them to provide guidance on configuring lift axles to meet diverse regulatory environments.
Adding lift axles is not as simple as bolting on an extra axle. It involves detailed engineering to ensure proper fitment, clearance, and integration with the truck's existing systems.
Driveline and Tire Clearance: Lift axles need sufficient clearance when the suspension is inflated or deflated. This is especially critical for steerable lift axles and steerable pusher axles that articulate during turns, requiring additional space to avoid interference with tires, frame rails, or suspension components.
Frame Rail Space: The truck frame must accommodate brackets and lifting mechanisms without interference from crossmembers or fasteners. Limited frame space can constrain axle placement options, so always consult a qualified installer.
Suspension Compatibility: The suspension system must be matched to the axle rating and tire size. For example, switching between “super single” tires and standard dual tires affects suspension travel and ground clearance. Mismatched components can lead to premature wear or damage.
Air System Capacity: Lift axles rely on air suspension and brake systems. Adding multiple lift axles increases air demand, requiring appropriate reservoir capacity and compressor sizing to maintain brake performance and suspension operation.
LUEN's product lines include American-type suspensions and axles engineered for optimal compatibility and durability, simplifying integration and reducing installation challenges.
Traditional non-steerable lift axles can experience significant lateral forces during tight corners and cornering, causing tire scrubbing, chassis wear, and premature component failure. Retracting these axles to avoid damage shifts the load to remaining axles, risking overload and compliance violations.
Steerable lift axles address these challenges by allowing the wheels to swivel and follow the vehicle's path naturally. This reduces tire scrubbing and chassis stress, mitigates potential damage to chassis components, improves maneuverability, and allows the steerable auxiliary axles to remain deployed and load-bearing while steering.
Steerable pusher axles-a type of steerable lift axle mounted ahead of the drive axles-are particularly effective in distributing weight and improving vehicle handling in tight turns.
LUEN's steerable lift axle offerings incorporate robust designs that enhance vehicle performance and reduce maintenance costs, making them a preferred choice for fleets seeking operational efficiency.
Retrofitting steerable lift axles onto existing trucks is increasingly popular but comes with challenges:
Supply Chain Constraints: Recent global disruptions have affected the availability of auxiliary axle components, causing delays.
Complex Installation: Traditional retrofit kits require significant labor and precise alignment, often resulting in extended vehicle downtime.
To address these issues, LUEN and other manufacturers have developed retrofit kits with improved mounting systems and alignment aids. These innovations reduce installation time and improve accuracy, minimizing downtime and cost.
When specifying lift axles, it is important to understand the difference between axle rating and suspension rating. The overall package rating is limited by the lowest-rated component. For example, a 26,000-pound axle paired with a 30,000-pound suspension will have a maximum rating of 26,000 pounds.
Additionally, operators must consider the jobsite rating-the load the truck can safely carry when lift axles are raised and the weight rests on fewer axles. Structural integrity of axle housings and frame components must be verified to handle these conditions, often with speed restrictions applied.
LUEN’s axles and suspensions are engineered to meet rigorous rating standards, ensuring safety and compliance under varying load conditions.
Lift axle deployment can be controlled manually or automatically:
Manual Controls: Typically located in the cab or on the chassis, allowing drivers or ground personnel to raise or lower axles as needed.
Automated Systems: Use sensors to raise or lower axles based on load weight, vehicle speed, or operational mode. For steerable lift axles, automation often includes lock-up mechanisms that engage when reversing to prevent unintended steering movement.
Regulatory requirements may dictate control placement, with some jurisdictions requiring controls to be outside the driver's reach.
LUEN supports a variety of control options compatible with their lift axle systems, providing flexibility to meet operator preferences and regulatory demands.
Selecting and installing the right lift axle system is a complex, engineering-intensive process that requires careful consideration of regulatory requirements, vehicle design, and operational goals. Whether choosing between lift axle vs liftable suspension, or upgrading to steerable lift axles for improved maneuverability and reduced wear, operators must collaborate with manufacturers like LUEN, upfitters, and dealers to ensure a compliant, efficient, and durable solution.