LOUISVILLE, Ky.-An industry task force will investigate the causes of ``zipper failures'' in steel-radial truck tires and determine what can be done to reduce injuries resulting from them. The effort will be spearheaded by the American Retreaders' Association, which hosted a public forum on zipper failures April 20 in Louisville on the eve of the group's 37th annual World Tire Conference & Exposition.
The meeting, attended by well over 100 people, produced little consensus as to the causes of zipper failures. However, it did conclude that much more needs to be known about them.
ARA Executive Director Marvin Bozarth, who has been assigned the job of organizing the task force, described zipper failures as semicircular-shaped sidewall ruptures, usually 12 to 36 inches in length, that occur after the steel radial cords in a tire's sidewall are weakened and break.
The broken steel cord filaments extending from the rupture give it the appearance of an open zipper, hence the name.
Zipper failures often are hard to predict, Mr. Bozarth said, and exert such explosive force that they can seriously damage anything-or anyone-nearby.
From the comments made at the meeting, it seems clear that tire manufacturers and dealers are sharply divided as to what causes zippers and how big a problem they pose.
During the two-hour forum, tire dealers and retreaders generally expressed a belief that the cause of these catastrophic sidewall failures is related to the steel-cord body construction of some radial truck and light truck tires.
However, technical representatives of six tire manufacturing companies who took part in the discussions generally held the view that zipper failures are neither widespread nor related to faulty tire construction, but are instead the result of user abuse such as underinflation, overloading or poor repairing, storage or maintenance practices.
Moreover, these panel members-representing Bridgestone/Firestone Inc., Goodyear, General Tire, Michelin North America, Kumho U.S.A. and Toyo Tire (U.S.A.) Corp.-said they're unaware of any forthcoming changes in tire construction that will reduce the possibility of zipper explosions.
Their collective advice to dealers, retreaders and others who must work with all-steel radials: Learn to live with the possibility of zipper failures by adopting stringent safety rules and careful maintenance practices to eliminate tire abuse and thereby reduce the threat of explosions and injuries resulting from them.
Not surprisingly, this did not sit well with some dealers and retreaders in the audience-including Peggy Fisher, president of Roadway Tire Co., a large truck tire retreading operation in Columbus, Ohio.
Even if zipper explosions were relatively small in number compared with other types of tire failures, as the manufacturers contend, they still represent an ``expensive and life-threatening'' problem, said Ms. Fisher, who added: ``I don't intend to live with it.''
The potential for serious injury or death arising from zipper failures puts tire service workers and the motoring public at risk and makes everyone involved in the tire distribution chain vulnerable to lawsuits, she said.
Tire manufacturers themselves are the most vulnerable, because they have the deepest pockets, she reminded the panel.
It is not acceptable to dismiss the problem simply as the result of underinflation, she said.
``Overloading and underinflation are not new problems,'' added Ms. Fisher, who said she had experienced the ear-splitting consequences of one such explosion in her own shop.
``Yes, (under)inflation is part of the cause-but it's not the problem,'' she said. ``It's the wick that lights the powder (prior to the explosion). The root cause is deeper.''
Furthermore, tires produced by some manufacturers are less susceptible than others to such sidewall explosions, Ms. Fisher said. Buyers of truck tires will come to realize this-and make their purchases accordingly.
According to Mr. Bozarth, zipper failures usually occur during inflation, when the internal pressure reaches about 40 psi. However, they can occur days after the tires are aired up.
Rust often is present in the broken steel cords, he said. However, no one knows whether it is a causal factor in such explosions, because rust also is found in tires where no failures have occurred.
Though zipper failures have been found in many sizes of all-steel truck radials, they are particularly dangerous in light truck tires, said panelist Edward J. Wagner of Tire Technical Services Inc. in Louisville.
Federal safety regulations, which require that larger truck tires be inflated in a protective safety cage, do not apply to light truck tires, he pointed out.
An 11R22.5 radial truck tire has a potential explosive force nearly equal that of a stick of dynamite, said Mr. Wagner, who frequently serves as an expert witness in product liability cases and is currently working on 18 involving zipper failures.
In most of these cases, the tires had been repaired, which he said raises an important question: Is it in the best interest of retreaders and other tire service providers to repair all-steel radials?
In the case of larger truck tires, most zipper failures appear to occur on the inside position of dual-tire applications, said Frank Timmons, vice president in charge of technical standards for the Rubber Manufacturers Association.
He, like the tire maker representatives on the panel, attributed most zipper failures to ``poor consumer inflation management or repair'' and ``tire abuse,'' such as chronic underinflation or overloading.
Mr. Timmons said the inside tire in dual applications is less likely to have its inflation checked and is therefore more apt to be run underinflated.
Dealers and retreaders have the ability to virtually eliminate the risk of such failures to tire service personnel, he said.
Remind customers verbally and in writing to keep tires properly inflated. ``Remember,'' he said, ``every tire your customers do not operate underinflated is one less possible zipper waiting to happen.''
Remove and carefully inspect any tire found seriously underinflated (having 80 percent or less of its recommended pressure) as well as any tire in a dual-application found with significantly less air pressure than its mate;
Establish and adhere to a strict inspection program-particularly for any radial tire showing evidence of underinflation, having a previous repair or removed from an inside dual position; and
Insist that workers carefully adhere to the procedures mandated by the federal Occupational Safety and Health Administration when servicing such tires.
However, dealers and retreaders at the meeting responded that zipper ruptures first began showing up about five years ago and have since gotten progressively more commonplace.
This has fostered suspicions that something having to do with these tires' construction lies at the heart of the zipper problem.
Dealer and retreader M. Terry Westhafer of Central Tire Co. in Verona, Va., told how he recently accompanied one of his employees to the hospital for treatment of minor injuries resulting from a zipper explosion. While there, Mr. Westhafer said ambulance attendants told him they had brought in two other workers that same week-both of whom had been injured in similar tire explosions.
As the question-and-answer portion of the meeting drew to a close, ARA President Michael W. Berra of Community Tire in St. Louis rose to suggest the formation of a task force composed of technical experts from both the tire retreading and manufacturing industries.
Mr. Berra described the mission of the task force as twofold:
To identify the causes of zipper failures and determine what can be done to prevent them; and
To learn the most effective ways to detect potential failures before they occur.
The task force also will assess whether existing safety procedures recommended by the industry and mandated by OSHA are adequate to protect such workers until the industry finds a solution to the problem.
``We need to pool our knowledge,'' he told manufacturers, retreaders and others at the meeting. ``Hopefully, we all agree that it's a problem and we'll all work to find a solution.''
Even if the industry would be able to prevent zipper failures by changes in tire construction, it would still take five to six years to eliminate the current more failure-prone tires from the distribution system, he pointed out.
The task force is expected to hold its first meeting on the subject within the next 90 days, the ARA later announced.
In addition to those previously mentioned, other members of the panel included: Ken Ball of Bridgestone/Firestone, Al Cohn of Goodyear, Guy Edington of Kumho, Andre Heijnen of General Tire, Bill Major of the Retread Manufacturers Association in the U.K., Jack McCammond of Michelin, Nick Powers of Hennessy Industries, Jerry Rogers of Lake Tire Service Inc. in Grand Rapids, Mich., and Dave Taylor of Toyo. Chuck Meier, a retired tire design engineer, formerly with Kumho, served as moderator.