WASHINGTON-Comments made by a top Ford Motor Co. polymer scientist in a court deposition go against the auto maker´s reasoning for recommending tires be replaced after six years, regardless of condition, tire industry officials said.
"Based on these statements, we would submit that Ford doesn´t have data showing a direct correlation between tire age and tire performance," said a spokesman for the Rubber Manufacturers Association, regarding the statements given in a Dec. 17, 2004, deposition by John M. Baldwin, the Ford polymer science technical specialist who leads the auto maker´s research in tire aging. Based on the results of Baldwin´s research, Ford decided to advise its customers to replace their vehicle´s tires after six years.
"We find this to be very contradictory with Ford´s actions," said Becky MacDicken, government affairs director for the Tire Industry Association, of Baldwin´s statements.
A Ford spokesman declined to comment regarding the Baldwin deposition.
Earlier, the RMA said neither Ford nor DaimlerChrysler A.G.-which will add the six-year tire replacement recommendation to its owners´ manuals starting with the 2006 model year-ever shared their tire aging data with either the association or its tire manufacturing members.
Baldwin was deposed in a case before the Texas 117th Judicial District Court. At the beginning of the deposition, Baldwin said it became obvious from studying some of the Firestone ATX, ATX II and Wilderness AT tires recalled in 2000 that the properties of the rubber were changing dramatically over time.
"If you put a new tire vs. a four-year-old tire on a road wheel and let it go...to failure, my belief is that an older tire would fail faster on any particular test," he said.
Later during the deposition, however, Baldwin seemed to qualify this statement. When asked whether older tires are less resistant than new ones to belt edge separations, he answered, "I´m not comfortable making that assessment yet, to be honest with you."
Baldwin disagreed with the assertion that oxidative aging occurs in all tires over time. "It depends on a lot of other factors."
He also disagreed with the assertion that oxidative aging of inflated tires has been well known for a long time, saying, "There´s not a lot of literature on it."
Discussing the results of oven aging tests on tires, Baldwin said, "Oven aging tires either unmounted or mounted with air for the two weeks has very little effect on the chemical and physical properties of the belt package rubber. Only when mounted with the 50/50 oxygen-nitrogen...do properties significantly change."
Baldwin said he planned to compare new and oxidatively aged tires to see if cracks began and grew more rapidly in the aged tires. He hoped to complete the work this summer.
At the end of the deposition, Baldwin said Ford wasn´t collaborating with any tire companies in its tire aging research, and he wasn´t aware at that time of any backlash from the tire industry regarding Ford´s study.
In March 2004, Baldwin told an audience at the Clemson Tire Industry Conference aging is a crucial element in tire degradation, and his research of the recalled tires demonstrated this.
"When you look at two vs. four years of service, peel strength had dropped 50 to 75 percent in the field," he said. "Obviously, the rubber´s changing."
The RMA and TIA are waiting for the creation by an ASTM committee of a testing protocol for tire aging. The committee-which includes a number of tire industry scientists and officials-is working in conjunction with NHTSA in the agency´s efforts to devise a tire-aging test for federal tire safety standards.
"There are so many variables involved that we honestly don´t know whether they´ll ever come up with an accurate test," MacDicken said. "This underlines our feelings that Ford was at the very least premature in its recommendations to its customers."