So, Do You Need a Nylon Cap?

By Adam Zagorin

Remember when Congress abandoned the 55-m.p.h. speed limit a few years ago? That may have helped pave the way for this wave of fatal blowouts.

Back in the 1970s, when the 55-m.p.h. speed limit was established, U.S. tiremakers were introducing steel-belted radials--now standard on most American cars, including the Ford Explorers. Even in the '70s the fatal consequences of tread separation were well known. And so were a number of remedies, including the use of nylon caps that form a tourniquet around the belts and rubber to hold them together. Nylon caps are widespread in Europe and other parts of the world, but with U.S. speed limits set low, most experts believed they weren't necessary in America.

In the mid-'90s, when Congress allowed the speed limit to go back up, the stress on tires rose dramatically. Even so, manufacturers insisted that nylon caps produced a more rigid tire with a rougher ride and argued that except for tires subjected to speeds of 110 m.p.h. or more, the synthetic overlays were not needed. Hence most major-brand tires used in the U.S. today lack nylon caps.

But did the manufacturers know the risks of not using the caps? A series of tests were carried out in 1997, 1998 and 1999 by Standard Testing Laboratories, which performs numerous tests for the industry. One popped up in a California trial that ended in June with a jury's awarding $15 million to a man who demonstrated that the tread of his Dunlop tire had collapsed in part because the company did not design a nylon cap into the tire. He is now a quadriplegic; the case is on appeal. According to plaintiffs' lawyers and experts, the STL studies document on video what happens to major-brand-name radials as their inflation is reduced: none of the tires suffer fatal tread separation if they have nylon caps. Last week Ford urged Firestone to recall its Wilderness AT tires in Venezuela because they lacked the caps.

Firestone engineers advocated the use of nylon caps in the '70s to head off the infamous tread-separation scandal on Firestone 500 radials. In this latest scandal, however, Firestone's replacement tires in the U.S. do not have nylon caps, except for a few Bridgestones shipped in from the parent company in Japan. Firestone argues that its tire problems are specific to one factory and not a matter of technology. Bridgestone, however, does sell the nylon cap Dueler for SUVs in the U.S. Like other nylon-fitted tires, they are higher-grade and cost $103 each, compared with just about $70 for a Firestone Wilderness.

--By Adam Zagorin. With reporting by Mike Eskenazi

With reporting by Mike Eskenazi