One of the considerations to make when buying heavy-duty vehicles is the suspension systems used in the vehicle. The suspension system in a semi-trailer determines its load capacity, maintenance needs, cost, and stability among other aspects.
The suspension system also influences the driver’s comfort and safety especially when driving on rough terrains. The function and reliability of suspension systems vary depending on the brand or model.
Hence, vehicle owners should consider installing suspension systems from brands with high-quality standards to avoid occasional breakdowns.
The most common types of suspension systems in semi-trailers include mechanical, air, rigid, and single-point suspensions. Each has its unique benefits and shortcomings.
The components and designs of the suspension system are also different. Most trailer manufacturers consider the end-use of the trailers when installing the suspensions.
For instance, semi-trailers that are used for heavy duties have suspension systems with a large load capacity. In addition, manufacturers can customize the suspension system to fit the owner’s specifications depending on the intended use. The benefits of each of the suspension systems are outlined below.
- Mechanical suspension
A mechanical suspension consists of reaction arms that keep the axles in semi-trailers horizontal in all types of motions. The arrangement of the arms varies depending on the brand. Most models have stops in their axles that keep the axles in the right position even in times of extreme motion.
Hence, one of the main benefits of mechanical suspension systems is that they are highly stable on all terrains. The load distribution in a heavy-duty vehicle with mechanical suspensions remains constant when brakes are applied.
The suspensions are cheap compared to other models and have a high load capacity. The high capacity enables the vehicles to carry out heavy-duty tasks.
Most of the models have a spring mechanism that reduces the vibrations sent to the trailers. Hence, the components or parts of the semi-trailers last for a long period because the rate of wear and tears is low.
Another advantage of these suspension systems is that they have low maintenance costs and require low and sometimes no lubrication.
Mechanical suspensions are recommended for semi-trailers and other heavy-duty vehicles that work on impassable or rough terrains. The suspensions have enough strength or capacity to handle such terrains.
- Air suspension
An air suspension system consists of polyurethane bags and rubber that are inflated using a compressor. The suspensions are considered the best substitute to leaf spring suspensions.
One of the main advantages of these air suspensions is that the driver is more comfortable when driving a vehicle or trailer with air suspensions. Such vehicles glide over bumps easily with less impact on the driver in terms of pain, noise, and harshness.
In addition, air suspensions have less vibration, which translates to less wear and tear on the other parts of the semi-trailer or truck. Reduced wear and tear helps drivers to save on maintenance costs.
Some of the models of air suspensions lift additional axles that are not in use. Such systems reduce the wear and tear on the tires. The driver can adjust the ride height depending on the terrain, speed, and load on the trailer.
The air suspension allows the driver to lower the height of the vehicle when empty. The height is usually high when the trailer is unladen and low when the trailer is at full load.
A lower height improves aerodynamics, vehicle control and steering, and stability. Air suspension systems keep the trailer balanced even when the load weight in unevenly distributed.
Since the trailers slide over bumps and their heights can be adjusted, air suspensions enable drivers to transport fragile items.
Additional benefits of air suspensions include increased versatility over different terrains. Drivers report that trailers with air suspension consume less fuel than other models of trailers. The improved control, stability, and aerodynamics translate to fewer road accidents.
- Rigid suspension
Rigid axle suspensions are among the oldest and simplest suspension systems. With these systems, the movement of one wheel is dependent on the movements of other wheels.
Modern trucks and trailers use independent axle suspension but some manufacturers still use rigid suspensions for various reasons. The suspensions have less comfort for the drivers but they are simple and cost-effective.
Rigid suspensions are cheaper than other independent models. They have low maintenance needs and hence their maintenance costs are low. The suspensions are robust and have a large load capacity.
Rigid suspensions are suitable for heavy load vehicles because they support large axle movements. In addition, their robustness makes them reliable.
The rigid axle beam provides firm support to both road wheels and stub-axles, which improves stability and wheel alignment.
With a rigid axle beam in place, the wheels remain perpendicular to the road as the trailer or truck moves. The driver can achieve an optimal tire tread contact with the road.
Consequently, the tires have a firm grip on the road and hence, the rate of wear and tear is reduced. The position and firm grip of the tires prolong their useful life, which reduces the cost of maintenance further.
The ride height remains constant whether the semi-trailer is laden or unladen. But it is better used for low speed, because its damping isn’t good.
- Bogie suspension
Drivers can choose bogie suspensions for their RGN trailers although the suspensions have narrow applications. Bogie suspensions have various advantages including an improved adhesion of tires on the road.
The suspensions enable the driver to lower the position of the engine and the center of gravity. Consequently, the driver can increase the stability of the semi-trailer or truck by adjusting the ride height.
Bogie suspensions have a high load capacity and hence they are suitable for heavy-duty transporters.
The suspensions reduce the impact on the body especially on rough terrains, which enhances the driver’s comfort. Drivers are keen on the road and cause fewer accidents when driving in comfort.
The road wheels with this suspension type are independent and their unsprung mass is lower compared to other suspension systems.
The suspensions are associated with less vibration, which not only increases the driver’s comfort but also reduces wear and tear on the trailer’s components.
Each suspension system has its advantages and disadvantages. The right choice of a suspension system depends on various factors including the type of cargo that the semi-trailer carries and the most used terrain.
The choice also depends on the highest weight of the cargo, weight variation, the required level of stability, and the turning frequency among other factors.
Hence, the driver must consider the intended use of trailers and the number of working hours when buying a semi-trailer. If the suspension is too light, it will cause impact damage and if it is too rigid, it will cause fatigue.
The approach should be getting a suspension system that keeps the trailer and cargo stable and the driver comfortable in all types of terrain.