Independent suspension is any suspension system that allows each wheel on the same axle to move vertically independent of the others. This is in contrast to other suspension axle systems where the wheels are linked by a solid axle beam or housing, commonly referred to a straight axle.

In the United States, approximately 60- to 70-percent of all major fire trucks are built with a custom chassis that is engineered, designed and built to meet a fire department’s exact needs. Custom chassis most often ride, handle, stop and set up at a scene better because they are developed with specific geographic elements and service applications in mind.

As part of a custom chassis design, the suspension system is a major component and consideration for fire departments. The needs of a department and the vehicle’s application can strongly dictate the design and the type of suspension used, but there’s no doubt that independent suspension systems offer superior performance.

In the mid-1990s, Pierce Manufacturing’s parent company, Oshkosh Corporation, developed the TAK-4® Independent Suspension System used on military, severe-duty and emergency vehicles.