A fire truck’s tires are both a major safety and financial concern for every fire department. Properly maintained, they will reduce waste and the risk of injury. This is where the rubber meets the road.
The manufacturers of commercial-grade truck tires, the ones we run on our fire apparatus, agree that the single greatest factor in poor tire performance is underinflation. Paying close attention to inflation pressures and to tires that have run underinflated has never been more important, considering the potential for sidewall ruptures, the value of retreadable casings, and the cost of tire related downtime.
In addition, underinflation can lead to separation of the tire’s tread from its casing; higher risk of road hazard to other vehicles when a tire fails; loss of fuel economy; uneven and irregular tread wear; higher downtime expense; and loss of casing durability.
Weigh in
The steer axle and drive-trailer axles carry very different weight loads. So the optimum air pressure could be different for the tires on each. You have to know how much weight a truck is carrying on each axle and tire.
Don’t have a scale that big in-house? At my former department we weighed all of our apparatus at the county landfill with the scales that they used to weigh commercial trash trucks to determine how much to charge for the load. You probably have access to such a facility, a highway weigh station or a commercial trucking terminal in your community.
The majority of tire manufacturers have load and inflation tables on their websites where you can find the optimal air pressure for your vehicle’s weight load. The URLs for all the websites, or hard copies of the tables, for each of the tire manufacturers represented within your apparatus fleet should be readily available to the personnel in the maintenance facility and fire stations.
Under pressure
The tire industry recommends checking inflation pressures once each week on all tires. This check should be made with a calibrated tire gauge or a gauge that is checked periodically with a gauge known to be accurate.
Always check inflation pressures when tires are cold. Never bleed air from hot tires to relieve normal pressure build-up. The normal increase in pressure due to service conditions will be 10 to 15 psi, and this is allowable in a radial truck tire.
Another valuable tip is to use a sealing metal or nylon valve cap or a quality air-through type cap. Plastic caps do not provide a secondary seal to the outdoor environment. And no cap at all allows dirt, water and other foreign materials into the valve. Their presence invites air leakage.
Tire inspection
Carefully inspect any tires that have been repaired or have cuts, snags or other penetrations. To find out, rub your open hand over the tread in several directions. Do you feel any edges? Does it feel smooth? If not, there are forces acting on your tires that are causing it to wear incorrectly. These forces can include alignment issues, incorrect air pressure or mechanical problems.
If it doesn’t look or feel right, more than likely something is wrong with the tire. Follow your department’s procedure for placing the apparatus out-of-service until the tire can be thoroughly inspected by a trained tire technician.
NFPA 1901: Standard for Motorized Fire Apparatus has included several tire-specific recommendations during recent updates to the standard. Those additions include:
- Rubber compounds improved for greater tread wear, casing life improved, and load capacities increased (1991 edition).
- Run-flat device that allows safe steering control during tire blow-out (2005 edition).
- Methods of tire pressure monitoring required (2009 edition).
Economic factors
Improper tire maintenance will not only rob you of expensive rubber in the wear of the tire, it also costs you fuel. And isn’t your budget for fuel being stretched enough already?
The concept of total wear-out mileage is easy to compute: off mileage minus on mileage gives you total miles driven. However, this is only a fraction of the real story.
Fuel-efficient tires will save your operation much more than using non-fuel efficient tires that might get a few more miles before wear out. Several of the major truck tire manufacturers have developed on-line cost calculators (like Continental Tire’s ContiCostCalculator) to assist departments in assessing the fuel efficiency of their current tires against available fuel-efficient products.
Tire manufacturers are also going high tech in their efforts to help fleet owners lower their overall driving costs by finding the right tire solutions. They’ve made online programs available that use Bluetooth-linked electronics and integrated software to measure tread depth, wear characteristics and air pressure.
By putting all of this into a management system database, a fleet manager can have real data that includes key performance indicators such as:
- Projected mileage and costs per mile.
- Dollar loss calculations due to improper air inflation and improper tire matching.
- Current dollar value of tires in the fleet based on tread depths and tire types.
- Forecast projections of upcoming tire needs based on fleet tire pull points.
- Reporting of conditions that require immediate action.
By becoming more knowledgeable about your fleet’s tires — one of your top operational expenses — you will be better able to get the most life out of them and your budget.
Tire care dos
- Maintain proper minimum inflation for the load carried per the manufacturer’s recommendations.
- Maintain mated dual tires at equal inflation.
- Use sealing-type valve caps.
- Check inflation at weekly intervals.
- Keep inflation air dry.
Tire care don’ts
- Don’t permit tires to operate underinflated.
- Don’t bleed air from warm tires to relieve pressure buildup.
- Don’t reduce tire pressure to obtain a softer ride.
- Don’t run with one tire of a dual assembly at low pressure or flat.
- Don’t inflate to cold pressures beyond rated rim capacity.
