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From incremental improvements to innovative bounds, fire truck designs are in a constant state of evolution and suspension systems are undoubtedly a crucial area of focus.

Suspension systems not only play a role in the overall performance and life of your vehicle but also the safety and comfort of its drivers. Additionally, superior suspension performance can protect the lifesaving equipment used by firefighters each day.

However, choosing the type of suspension system that is best for an individual department depends a lot on the type of service that is planned for the vehicle. When evaluating suspension types, a series of considerations need to be made such as, the type of apparatus and planned usage, budget, weight carrying capacity and more.

Below, we review independent suspension systems and discuss the four ways these systems help improve apparatus performance

Independent Suspension Systems for Custom Fire Apparatus Chassis

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.

In 2001, Pierce introduced the TAK-4® Independent Front Suspension (IFS) System on custom built Pierce chassis to provide a better road feel, control and smoother ride over any kind of surface.

Pierce now also offers TAK-4™Independent Rear Suspension (IRS) which applies the same military proven performance to the rear suspension.

For the highest level of maneuverability, Pierce offers the TAK-4 T3, which combines the advantages of TAK-4 IRS with a mechanical rear steering system.

Here is a comparison of Pierce’s TAK-4 suspension systems:

  TAK-4 Independent Front Suspension (IFS) TAK-4 Independent Rear Suspension (IRS) TAK-4 T3 IRS with Tight Turning Technology
Custom Chassis Enforcer™, Impel®, Velocity® Enforcer, ImpelVelocity  Enforcer, ImpelVelocity
Load Ratings 18,000 - 24,000 lb 24,000 - 52,000 lb 24,000 - 52,000 lb
Cramp Angle Up to 45° N/A Up to 9°
Wheel Travel

Up to 10"

Up to 14" Up to 14"
Dual Steering Gear Standard N/A Standard
Suspension Spring Type Torsion Bar Coil Coil 

Simplified Maintenance

Fire Truck TAK-4 Simplified Maintenance

The TAK-4 design not only maximizes a truck’s performance, it minimizes the wear and tear on your equipment and streamlines the maintenance process. There are no u-bolts on the front axle, no adjustments needed for the caster angle, and no need for lubricating the heavy-duty ball joints. Your rig spends less time in the shop and more time on the street.

Imperative Periodic Inspections

With a vast service network, Pierce provides you with trained certified technicians to perform routine maintenance and inspections that keep your vehicle running at its peak.

How Independent Suspension Improves Fire Truck Performance

1. Ride Quality & Control


Compared to a standard leaf suspension, independent suspension delivers outstanding ride quality and vehicle control. Some systems offer up to 16” of suspension travel, a softer wheel rate, robust design and independent wheel movement – keeping tires on track for improved overall handling and performance. Independent suspension systems will provide two, to two-and-a-half times wheel travel distance over the spring systems. Superior ride quality reduces stress not only on occupants but also gear, components and the vehicle.

2. Maneuverability


Greater maneuverability, turning radius and lane-to-lane turning are other benefits of independent suspension systems. Specifically, Pierce’s TAK-4 Independent Suspension System provides fire trucks with the tightest turning radius which can safely and effectively be maneuvered into strategic locations when responding to a fire with steering at the front and rear of the vehicle. The maximum front steering angle is 45-degrees and proportional rear steering angles at the rear allow maneuverability and mobility to be maximized, while utilizing the mechanical rear steering system.

3. Steering & Braking

TAK-4 IRS Reduced Road input on a paramedic vehicle

In straight axle suspension systems, when one wheel strikes and obstacle, the entire axle tilts. This will cause the opposing wheel to tilt inwards or outwards, preventing maximum tire interface with the ground. The effect can cause an imbalance and decrease in steering control causing heavy vehicles to be less responsive in cornering or braking scenarios.

With the TAK-4 Independent Suspension System, the vehicle allows for larger front brakes which transfers weight quicker to the front wheels. The lower wheel rates, made possible by a torsion bar, smooths out the road better than any straight axle rig because the wheels are allowed to be m

ore responsive and independent to the road surface. This not only maximizes performance, but minimizes wear and tear on equipment, reduces maintenance and saves on brake repairs. In fact, the system shortens stopping distance by 23-percent, has a 45-degree cramp angle and improves ride quality by 340-percent (as measured by accelerometer testing).

4. Load Carrying

Integrating a higher rated front axle allows for greater load carrying capacity which enables firefighters to add more features and equipment to fire apparatus. This may include front suction or air condition that won’t exceed gross vehicle weight restrictions. With Pierce’s TAK-4 Independent Suspension System, a maximum front axle weight rating of 24,000 lb. is possible with 425/65R22.5 tires.

When selecting fire apparatus suspension systems, a focus on optimizing safety, stability, maneuverability, ride quality, load capacity, simplified maintenance and more are all important considerations. The advancements in independent suspension systems have provided those in the fire service with many advantages over other suspension systems. The superior ride quality, enhanced operating features and the added confidence that the driver is in control of the vehicle, are all unparalleled qualities that continue to evolve with design and technology advancements.

Do you want to learn more about fire apparatus suspension systems that offer a high-performance, dramatically smoother ride with outstanding steer-ability?

Experience a better ride for you, your crew and your equipment by contacting an experienced Pierce Manufacturing representative.

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Topics: Products, Maintenance/Service, Apparatus Orders, Fire Industry

About Pierce Manufacturing
Pierce Manufacturing Inc., an Oshkosh Corporation [NYSE: OSK] business, is the leading North American manufacturer of custom fire apparatus. Products include custom and commercial pumpers, aerials, rescue trucks, wildland trucks, mini pumpers, and homeland security apparatus. In addition, Pierce designs its own foam systems and was the first company to introduce frontal airbags and the Side Roll Protection system to fire apparatus. To learn more about Pierce, visit

About Oshkosh Corporation

At Oshkosh (NYSE: OSK), we make innovative, mission-critical equipment to help everyday heroes advance communities around the world. Headquartered in Wisconsin, Oshkosh Corporation employs approximately 17,000 team members worldwide, all united behind a common purpose: to make a difference in people’s lives. Oshkosh products can be found in more than 150 countries under the brands of JLG®, Hinowa, Power Towers, Pierce®, MAXIMETAL, Oshkosh® Defense, McNeilus®, IMT®, Jerr-Dan®, Frontline™ Communications, Oshkosh® Airport Products, Oshkosh® AeroTech™ and Pratt Miller. For more information, visit

®, ™ All brand names referred to in this news release are trademarks of Oshkosh Corporation or its subsidiary companies.

Forward Looking Statements

This news release contains statements that the Company believes to be “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact, including, without limitation, statements regarding the Company’s future financial position, business strategy, targets, projected sales, costs, earnings, capital expenditures, debt levels and cash flows, and plans and objectives of management for future operations, are forward-looking statements. When used in this news release, words such as “may,” “will,” “expect,” “intend,” “estimate,” “anticipate,” “believe,” “should,” “project” or “plan” or the negative thereof or variations thereon or similar terminology are generally intended to identify forward-looking statements. These forward-looking statements are not guarantees of future performance and are subject to risks, uncertainties, assumptions and other factors, some of which are beyond the Company’s control, which could cause actual results to differ materially from those expressed or implied by such forward-looking statements. These factors include the Company's ability to successfully integrate the AeroTech acquisition and to realize the anticipated benefits associated with the same; the risks associated with international operations and sales, including compliance with the Foreign Corrupt Practices Act;  the Company’s ability to comply with complex laws and regulations applicable to U.S. government contractors; cybersecurity risks and costs of defending against, mitigating and responding to data security threats and breaches impacting the Company; the Company’s ability to successfully identify, complete and integrate other acquisitions and to realize the anticipated benefits associated with the same; and risks related to the Company’s ability to successfully execute on its strategic road map and meet its long-term financial goals. Additional information concerning these and other factors is contained in the Company’s filings with the Securities and Exchange Commission. All forward-looking statements speak only as of the date of this news release. The Company assumes no obligation, and disclaims any obligation, to update information contained in this news release. Investors should be aware that the Company may not update such information until the Company’s next quarterly earnings conference call, if at all.

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