Jason Estep
Responding to and from incidents has traditionally been a leading cause of firefighter fatalities and injuries. It is an area that requires constant attention and improvement. Think about the changes we've seen in apparatus safety during the past 20 years. We have enclosed cabs, added reflective striping on all sides of apparatus, installed seat belt monitors and signed seat belt pledges, installed tire pressure monitors, and removed loose items from the cab-yet we are still having the accidents. Why? I think the answer is two parts: first is driver training. We have to make sure that the people driving these rigs are properly trained to handle the apparatus. I could write for hours on driver training, but we'll leave that for another time. The second part of the answer is tire maintenance, or the lack thereof. Tires are an overlooked maintenance item and are more than likely a contributing factor to apparatus incidents, although it is often overlooked by investigators.
As firefighters, we take great pride in our equipment, always making sure that it is ready to respond at a minute's notice. However, we often overlook the most important part of the apparatus-the tires. I know they're black and round; we kick them to make sure they have air, and we usually spray tire shine on them for a parade. How much more do we need to know about a tire? We could all stand to gain a little more tire knowledge. Basic tire maintenance only takes a few minutes and is actually very simple, but it is important to understand the purpose, use, and limitations of a tire to properly maintain it.
Tire Construction
First, we need to understand how a tire is constructed. A radial tire is made up of six main parts: the inner liner, carcass ply, beads, sidewall, crown plies (belts), and tread. The inner liner is the tire's air chamber, making tubes a thing of the past. Usually made of a synthetic rubber called butyl rubber, it is nearly impenetrable by air and water. However, over time it can allow for slight air loss, so make sure you check your tire pressures. The carcass ply is the layer above the inner liner, often made of textile cords or steel wire (or cables) bonded into the rubber. These cables are largely responsible for determining the strength of the tire. The bead is the area of the tire that seals to the rim. The sidewall protects the side of the tire from impacts with curbs, rocks, and other road hazards. This is also the area that important tire details can be found such as tire width and speed rating. The crown plies or belts provide a rigid base for the tread and serve as protection for the carcass ply and inner liner. Traction, propulsion, braking, and cornering are all provided by the tread of the tire, which is designed to resist wear, abrasion, and heat.
Multifunctional Parts
Tires are one of the most, if not the most, critical components on a fire apparatus. Most parts of a fire truck perform one function. Tires on the other hand have numerous functions that are vital to safe responses. The tire's first job is to support the weight of the apparatus. Did you know that gross vehicle weight rating (GVWR) depends on properly inflated tires? A pressure loss of just five pounds per square inch (psi) in front tires can often be enough to lower the weight- carrying capacity of the tire below the weight capacity of the front axle.
The tire also acts as part of the suspension, softening the impact from the road. Tires that are below the recommended tire pressure can severely affect the handling of the apparatus, especially when dropped off the road or on rough roads. Tires transmit propulsion and braking power to the road, and they are a critical piece of the steering system. Tires that are underinflated have longer stopping distances than tires with the correct air pressure. This is very important considering fire apparatus already have a stopping