By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl

By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl

By Bob Albano

Air-ride suspensions have steadily increased in popularity in nearly all segments of the trucking industry. Approximately 75 percent of the trailers manufactured today and almost all highway tractors use air-ride suspensions.

Air has even proliferated into the specialty segments of the trucking industry. It is not uncommon to find air-ride suspensions on heavy-duty vehicles that operate in extremely rugged environments - dump trucks, refuse, logging vehicles, and even concrete mixers. Following this logical progression, the migration from leaf spring suspensions to air ride is gaining momentum on fire and rescue vehicles. Specifying the right suspension should be a high priority for decision makers in this industry. Suspension systems affect the performance and life of the vehicle, frequency of maintenance, and comfort and safety of the operator. Upgrading to an air-ride suspension typically results in less than a one percent increase in the total cost of an apparatus, a great value for benefits gained.

What Factors Control Ride Quality?

Suspensions with a lower natural frequency reduce the force transmitted to the vehicle, which improves ride and vehicle protection when properly engineered. Natural frequency includes the spring rate of the suspension and the amount of weight supported by the suspension. The spring rate of the air springs is a measure of the vertical stiffness of the air springs or how much the suspension deflects for a given load being carried. The natural frequency of a suspension will increase if the suspension spring rate is increased or decreased. Because of a softer spring rate, air suspensions provide greater equipment protection over traditional mechanical suspensions. This is because of the air springs’ ability to cushion the equipment and passenger load. Outstanding ride produces superior driver and passenger comfort while helping to protect critical, lifesaving equipment and costly electronic components from excessive vibration and road inputs.

Understanding Roll Stability

Roll stability is a measure of how well the suspension and chassis resist rolling or swaying, especially when encountering a turn. A vehicle’s roll stability can be measured in two ways: (1) determining the maximum cornering speed before reaching the rollover threshold (when tires lift off the ground), and (2) measuring the amount of roll that occurs for a given turn at a given speed (the roll angle). Many elements of a vehicle’s design play a factor in determining its roll stability. Roll stability for a fire and rescue vehicle is influenced by the height of the center of mass of the truck body and the axle track width. These factors can have the greatest impact on the roll stability of the vehicle.

While suspension roll stiffness contributes to roll stability, it represents only one component of the equation. The chassis’s flexibility and tire stiffness, for example, must also be considered when determining the truck’s overall roll stability. Air-ride suspensions have come a long way over the past few decades, and we’re now at the point where properly engineered air-ride suspensions can deliver roll stability near that of a steel leaf spring suspension. For fire and rescue vehicles, higher rollover thresholds allow improved vehicle performance during the challenging, evasive maneuvers that are experienced when rushing to the scene of an emergency.

So, how can the vehicle’s suspension affect roll stability? The level of roll stiffness provided by a suspension is the best way to directl

Chris Mc Loone

We’ve been reading a lot about rescue trucks during the past few months.

Bill Adams has taken us through the specification process and discussed the myriad options to consider when purchasing one. This month, Adams and Ricky Riley talk about the pros and cons of walk-in or walk-around rescue in our “FA Viewpoints” department, and Peter Ong’s cover story profiles a unique rescue rig from the San Diego (CA) Fire Department. Tired of rescue trucks yet?

During the past few months, we’ve also talked about embracing our future fire service leaders as well as the fire trucks of the future. Taking delivery of a new rescue truck at my fire company in the past year and watching our future leaders get all of our trucks ready leading up to the Independence Day holiday have afforded me the opportunity to reflect on both.

First, regarding the truck, the truck committee had its hands full in the beginning planning stages for the new truck. There are size restrictions in the firehouse, both height and length, so the new truck couldn’t be any taller and not much longer than the one it was replacing. But one debate was whether to go with a walk-in or walk-around. The truck committee ended up going with a walk-in but acknowledged a need for storage by shortening the walk-in area. So, after hearing about how the committee went back and forth before coming to a consensus, it was interesting to read Adams’s and Riley’s opinions on walk-in and walk-around rescues.

It’s also amazing how things have changed since 2002. We read in these pages every month about new technologies and innovations, but sometimes it’s hard to realize how far we’ve come until you see two trucks side by side. Equipment mounting advances are obvious on the new rig. And, all the compartments have LineX applied.

There are also some things you don’t see. For example, LED lighting on this truck means the new one has a smaller generator. All roll-up doors and LED strip compartment lighting mean no more lights in the doors and along compartment walls with bezels that can get pretty banged up over time.

One noticeable difference is the lack of “belly boxes” on the new truck. We just never had any luck with them. That is not to say that other fire companies wouldn’t find tremendous value in them, but they just didn’t work for us. All in all, our truck committee did a good job building the right rescue truck for Weldon Fire Company.

Moving to the future leaders and younger firefighters, this month, I’ll have 24 years in the company. Just recently at Fourth of July prep, a fellow member who joined in 1993 and I were discussing parade prep back then. We talked about spray painting the wheel wells and rolling around underneath the trucks with a pressure washer. I will say this: Thank goodness for newer floor coverings. Our 1989 Saulsbury rescue was a walk-through, and there was a lot of diamond plate for the rookie to polish.

Sometimes it’s beneficial to just step back and sort of take in everything that is going on, remembering that you were once the rookie or young firefighter, working hard on the trucks, learning just how much it takes to get them ready, and the energy you brought to the process. As we’ve been preparing the trucks, especially the new rescue, it’s been a pleasure to watch our younger firefighters - a few of whom were invited to participate in the truck committee for the new rescue - working hard, taking pride in the appearance of the rigs, and ge