Vehicle maneuverability is a measure of how well a driver can make a vehicle follow a particular path. For most vehicles, it is based simply on the turning radius — the shorter the turning radius, the better the maneuverability.

Many departments don't consider maneuverability when they specify an apparatus. They select the chassis configuration and components based on price, personal preference or some other factor with the assumption that the resulting vehicle will have adequate maneuverability. Unfortunately, that isn't always the case.

Some apparatus can't turn sharply enough to go around tight corners in congested areas without running up on the curb. Others can't turn quickly enough on narrow roads without backing and filling several times. On a few apparatus, the tires are able to turn in a tight radius, but the front overhang of the cab or bumper hits objects as the vehicle swings around.

There are two types of turning radius to consider. The curb-to-curb turning radius is the path the outside front wheel follows when the steering wheel is turned to the limit on one side or the other. It is useful when there are no obstructions above the level of the curb. The wall-to-wall turning radius is the path the outermost and forwardmost portion of the chassis or body follows — for example, the outer corner of an extended front bumper. The wall-to-wall radius is generally larger than the curb-to-curb radius. It's useful when there are walls, posts or other obstructions next to the road. Ask for both when you consider a particular vehicle.

To avoid problems with turning radius, here are some points you should consider when you specify your next apparatus.

Front wheel cut. The front wheel cut, or cramp angle, is the maximum angle of the front wheels during a turn. The greater the wheel cut, the smaller the turning radius. Manufacturers advertise the inner wheel cut because it's larger, but the turning radius is determined by the outer wheel cut. The actual inner and outer cuts vary depending on the axle, axle track, wheel offset, tires and interference with frame-mounted components. They also vary between left and right turns. When comparing wheel cuts, always ask for the actual left and right outer cuts based on the "as-built" specifications, not the advertised maximums.

Axle track. Wide-track front axles space the wheels farther away from the frame rails to improve clearances or allow the use of larger tires. They are commonly used on custom chassis to support more weight on the front of the apparatus while still maintaining an acceptable wheel cut. Commercial chassis apparatus carry less weight on the front and generally use standard-track front axles. Depending on the vehicle configuration, standard-track axles can be lighter, less expensive and have somewhat sharper wheel cuts.

Tires. Bigger front tires will hit the frame or frame-mounted components at less of a turning angle than smaller tires. Whether you specify big tires to carry more load on the front axle or to provide more support on soft soils, be aware that you may be limiting the turning radius at the same time.

Wheel off-set. Different wheels space the tires farther or closer to the frame rails depending on the off-set or "dish" of the wheel. The closer the tires are to the frame, the more restricted the wheel cuts will be.

Axle stops. Some apparatus have improperly adjusted front axle stops that limit the wheel cuts before the tires actually hit anything. Always check the axle stop settings when taking delivery of a new apparatus, and re-check the settings if drivers start to complain of restricted maneuverability.

Wheelbase. It should come as no surprise that aerials, heavy rescues and other vehicles with long wheelbases are more difficult to maneuver than vehicles with shorter wheelbases. The turning radius is directly proportional to the wheelbase: Double the wheelbase, and the turning radius doubles as well.

Specifying an apparatus for good maneuverability involves a trade-off between all of these factors and more. Custom chassis apparatus tend to carry more weight on the front axle, which requires larger tires that may increase the turning radius. On the other hand, custom chassis apparatus also tend to have somewhat shorter wheelbases, which may decrease the turning radius. Shorter bodies and shorter cabs also help decrease the wheelbase. Changing the load distribution to shift weight to the rear may allow smaller front axles with better wheel cuts. Consult an apparatus manufacturer for specifics.

If you're tired of driving big, unwieldy rigs, take some time to consider ways to improve vehicle maneuverability the next time you specify an apparatus.