Apparatus Suspension: A Lot Is Riding on It

BALTIMORE— There’s arguably nothing more important on fire apparatus than the chassis and suspension. It’s the very bases upon which everything else rides, including the department’s most valuable asset, firefighters.

That’s why a whole class was dedicated to just chassis and suspension review at Firehouse Expo’s Emergency Vehicle Technician Mechanics Clinic.

Donn Gutshall, fleet superintendent in Hampden Township, Pa., presented information on the important factors in determining what chassis components work best and how to specify the correct equipment for the various duty cycles fire departments experience.

The EVT Mechanics Clinic was an added feature Firehouse Expo attendees were offered. Throughout the event, representatives from apparatus and fire equipment manufacturers and other experts offered how-to and troubleshooting sessions all interested attendees. Additionally EVT Certification testing was offered to those who were interested.

During his presentation, Gutshall stressed the importance of checking the weight of apparatus and keeping the loads evenly distributed as a way to make sure the suspension and chassis perform as expected.

“We’ve all seen it, someone finds a piece of equipment in a closet and says it needs to be on the rig,” Gutshall said. “Soon, everything becomes off balance.” He said he’s seen apparatus out of balance by as much as 1,000 pounds from side to side.

Tire pressure needs to be maintained to manufacturers’ specifications too, he said, noting that it’s not unusual to have firefighters fill tires to 95 psi when they require 120 psi to get a better ride.

According to the National Fire Protection Association tires are supposed to be replaced every seven years at a cost of up to $1,000 each, Gutshall said, noting that lower than recommended pressure can wear tires out quicker at an additional expense.

Moving on up to the wheels, Gutshall recommended brushed aluminum which he said is attractive and lower maintenance than the highly polished aluminum wheels which can turn ugly in a few years without proper care.

And when it comes to replacing wheels, Gutshall is a proponent of torque sticks to prevent wheels from being over tightened and break the studs.

Moving up to the suspension, Gutshall said there are several alternatives ranging from air rides, to tapered springs, to rubber blocks and all have advantages for different applications.

Air ride suspension offers a smooth ride and can be easily changed out if they’re damaged or blow out, Gutshall said, noting that the apparatus is out of service, however, as soon as the air bag is damaged.  Also, airbag leveling valves should be mounted as close to the chassis as possible to maintain optimal balance when loaded, he said.

Broken leaf springs need to be changed out as soon as they’re discovered broken, but unless the top leaf is broken, they can at least be driven, Gutshall said. Apparatus specified with leaf springs should also have bodies specified with access panels to make removal and replacement easier, he said.

Regarding steering, Gutshall said steering boxes should be mounted on the frame rails, and not on brackets that can be broken causing potentially catastrophic harm.

It’s also important that the lowest part of any suspension component, including axles, be at least eight inches off the ground to prevent damage, Gutshall said, adding that all hoses, brake lines and similar components must be fastened as well to also to prevent damage to critical control components.

Gutshall also spoke about the different kinds of braking systems, including drum and disk brakes, recommending that out-board disk brakes be specified to prevent the need of having to remove axles to change brake systems. And, although they can be pricey, Gutshall recommended Telma brake retarders for apparatus.

Fire apparatus with proprietary suspension systems can also be problematic, Gutshall said, noting that if something breaks, fire departments are at the mercy of the manufacturer to get replacement parts. If brand name suspension systems are specified, fire department mechanics can go to virtually any truck parts store and get the necessary parts to fix the apparatus.

He recommended that single-rail frames be specified, especially in the Northeast which often has corrosive road treatments applied during the winter to melt snow and ice. Those chemicals can get trapped between the frame rails and push them apart over the years causing damage.

Painting the frame rails a light color, like gray, can help mechanics discover frame flaws like rust and cracks, he said, noting that it also makes it easier to spot leaks too.

Gutshall also said that components should be bolted to the frames, not welded so when they need replacing, they can simply be unbolted and replaced. Having to cut cross members or generators or any other welded item on an apparatus frame can be a headache given the complexity of hydraulic lines, wiring and all kinds of other items found under fire trucks, he said.

Inspections, lubrication and cleaning will all pay dividends in keeping apparatus on the road for extended periods of time, Gutshall said.

“Get the vehicles off the ground when you’re lubricating the chassis and cleaning it when you can,” Gutshall said. “Check the fluid levels and the u-bolts when you’re under there. Check for rust and crackw and anything else you can. You’ll be better off for it.”

Firehouse is opened the entry period for the 2014 Emergency Vehicle Technician of the Year award. Enter your department's EVT today, click here to learn more.