An inspection of the sidewall and bead may not be enough. NFPA 1915 gives guidelines for outside visible inspection. Sometimes “weather” cracking in sidewalls may not be interpreted correctly. Not all damage is visible. Although I could not find any hard information from tire manufacturers for replacement for old tires, one thing tire manufacturers agree on is that as the tire ages, tire failures accelerate proportionately. We all know rubber deteriorates, deforms and hardens with age. Deterioration also accelerates with extreme temperatures, ozone, ultraviolet rays and improper air pressures. Excessive washing or dressing using alcohol or petroleum-based cleaners also accelerates “weathering.”

With steel belt tires now standard equipment, we sometimes see the outside steel belt separating. This is due to the oxygen and moisture leaking through the tire. A tire loses between 2% and 5% of air per month. This rusts the steel belts after a period of time. Aircraft and some truck fleets inflate tires with nitrogen to help stop this problem.

Even through the United States Congress has introduced bills to address new tire requirements, including testing for aging, the National Highway Traffic Safety Administration (NHTSA) has deferred testing for aging for two years. As a result, there is no tire replacement standard to go by other than our own experience. From searching Web sites, I found the general consensus is to replace tires 5- to 7-years from the DOT date on the tire. The tire starts aging as soon as the tire is manufactured. In the warmer climates, replacement may be recommended sooner (due to higher ozone and smog). A Web site for tire retreaders states, “a tire casing more than 6 years old might be suspect to closer inspection.”

The date a tire is made is imprinted on tire sidewalls at the end of the long DOT number. For tires manufactured before the year 2000, the last three digits represent the week (two digits) and the year (one digit) of production. So, if the last three digits are "229," the tire was produced in the 22nd week of 1999. Tires made after Jan.1, 2000, have a four-digit date code at the end of the number. The first pair of digits represents the week of production, and the last two digits represent the last digits of the year of production. So, "2200" as the last four numbers means the tire was manufactured in the 22nd week of 2000.

Don’t forget to schedule and budget your tire replacement. Let safety, not cost, be a priority when tires are concerned.
___

Reprinted with permission from "The Wrench," the online newsletter of the Illinois Fire Apparatus Mechanics Association. For more information, go to www.ifama.net.

Terry Eckert is the president of the Illinois Fire Apparatus Mechanics Association and has more than 35 years experience in the fire service. He is a past voting member of the NFPA 1071 EVT Professional Qualifications Technical Committee and the NFPA 1915 Fire Apparatus Preventive Maintenance Program Task Group. Terry is currently a board member of the Emergency Vehicle Technician Certification Commission and is certified as an EVT Master Level III Fire Apparatus Technician.