Waste Advantage Magazine

Spec’ing the right suspension for your truck


Courtesy of Waste Advantage Magazine

Trucks are expensive. As with any piece of expensive equipment, priority should be taken when spec’ing components that have an effect on the performance of the vehicle, the life of the vehicle, the frequency of maintenance, component lifecycle costs, and the comfort and safety of the operators. Without a doubt, spec’ing the right suspension should be a high priority for decision makers in the trucking industry.

One of the first suspensions widely used in the trucking industry was the walking beam or equalizing beam tandem suspension. Walking beam suspensions are able to equalize the truckload between two drive axles by allowing the wheels to adjust to uneven terrain by way of a central pivot point. Some walking beam suspensions contain steel leaf springs designed to offer support and stability. Walking beam and steel leaf spring suspensions are very robust and demonstrate good stability characteristics, with adequate ride quality for most operations.

The next generation of suspensions incorporated rubber into the springing medium. As applications became heavier and more severe toward the middle of the 20th century, rubber block suspensions were designed to increase stability over mechanical spring systems. Later developments in rubber technology provided designs that offered an improvement in ride over traditional walking beam and spring systems by dissipating road shock via rubber bolster springs. Some rear suspensions were designed as a twostage system to offer excellent ride quality in the unloaded condition and additional stability when the truck is loaded and the center of gravity increases.

Compelled by the drive to improve ride while maintaining the same level of stability and handling, suspension manufacturers in more recent years began developing systems that incorporate air spring into the suspension design to provide even greater ride quality. In such suspensions, the air springs adjust to maintain proper ride height as the load of the vehicle changes, thereby providing a relatively constant ride whether loaded or unloaded. Air springs were first used on trailers and on-highway tractors to protect cargo from excessive road shock and to provide enhanced comfort for the driver. However, recent developments over the past decade have produced vocational air suspension designs that offer greater protection of the cargo, chassis and body equipment in severe environments.

Over the years, research and development, intense testing and experience have resulted in current designs developed to address past shortcomings. As a result, the components used in air suspensions have become more robust and lighter weight. More recent air suspension products have also been developed to increase stability and handling, and to package within the tire envelope for component protection. In addition, more advanced designs use system geometry that controls torque windup and corresponding frame rise, and significantly reduces driveline vibration that can cause undue wear and tear on the chassis and body equipment.

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