Purchasing a new truck for your fire department is no small undertaking. Unless you’re a privately owned contractor, chances are you’ve got an apparatus build committee, a small timeline, and a tight budget. Making the right decision on your truck’s size and configuration is key.

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The cab-to-axle (C/A) measurement on an F-550 or Ram 5500 medium-duty chassis is a critical consideration when choosing a fire or rescue truck build. It’s the distance from the rear of the cab to the center of the rear axle. The longer the C/A, the more storage space the truck will have, but the less maneuverable it will be.

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Wildland firefighters need trucks with excellent maneuverability, so they typically choose trucks with shorter wheelbases and C/As. This allows the truck to have a better breakover angle, which dictates the clearance the undercarriage has over obstacles that pass between the front and rear axles—rocks, fallen branches, stumps, you name it. This is important for navigating tight spaces and obstacles in wildland environments.

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Urban firefighters may need trucks with more storage space, so they may choose trucks with longer C/As. This allows for more cab-access doors and more room for equipment, such as rescue gear.

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Don’t confuse wheelbase with C/A. Wheelbase is just that: the distance between the centerline of the front axle and the centerline of the rear axle. A standard cab truck with an 84” C/A is similar in length to a four-door Super Crew truck with a 60” C/A. For example, the F-550 chassis can be configured with a standard cab, extended 2-door super cab, or 4-door super crew configuration. If you need four full-sized doors but want to keep the wheelbase as short as possible, a 60” C/A is the configuration to go with.

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There are other options for varying cab length and storage relative to C/A, but it’s best to consult with a professional to determine the best configuration for your needs.

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Facts from outside sources:

• The National Fire Protection Association (NFPA) 1901 standard specifies the minimum requirements for fire apparatus, including the C/A measurement.
• A study by the Fire Protection Research Foundation found that trucks with shorter C/As have better maneuverability and are less likely to roll over.
• A study by the National Institute of Standards and Technology found that trucks with longer C/As have more storage space and can carry more equipment.

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There are some other mix-and-match options for varying cab length and storage relative to C/A, but a blog doesn’t offer nearly enough space to explain them all. So sometimes, the best thing to do is to get in touch with us at QTAC™ to create a build to meet your needs down to the letter. In fact, there’s nothing our design and build teams like more than helping customers create exactly what they need to meet your mission.

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