New questions arise over specifications ordered by Ford
WASHINGTON -- As
Ford Motor Co. continues a $3 billion quest to replace Firestone Wilderness
AT tires on its vehicles, new questions are being raised over whether
specifications Ford ordered for the tires played a role in the above-average
failure rates.
Ford's engineering specifications to Firestone, which received scant
attention in congressional hearings last year, is likely to come up in the next
round of hearings and in hundreds of product liability lawsuits pending around
the country.
One of the most pressing questions is why Ford accepted Wilderness AT tires
with a low-temperature rating for the Explorer, a sport-utility vehicle with a
relatively small load factor. An Explorer can safely carry fewer passengers and
cargo, compared with similar SUVs.
"It's certainly a concern that has been raised," said Ken Johnson, spokesman
for the House Energy and Commerce Committee.
The House panel has been conducting an investigation into SUV tire safety
since January. It has asked every automaker and tire manufacturer for extensive
data about the tires equipped on SUVs and other light trucks.
On Friday, the committee wrote to the National Highway Traffic Safety
Administration seeking help in sorting through the charges Ford and Firestone
have lobbed at each other. The panel specifically asked NHTSA to look into
safety questions about the Explorer, including whether its handling capabilities
contribute to accidents.
Until now, NHTSA has focused largely on the role of the tires.
"We have become increasingly concerned about the allegations made by both
companies. We have asked NHTSA to help us sort out this controversy," Johnson
said.
Many safety advocates have raised questions about whether the typical SUV
tire is robust enough to withstand today's high-speed driving habits, especially
when SUV drivers treat their vehicles like cars, paying little attention to the
number of passengers or the amount of cargo they carry.
Many of the failed tires came in warm-weather states where heat created from
road friction is a big problem. In lawsuits around the country, plaintiffs and
their attorneys have said Ford's tire specifications, combined with a
recommendation to lower tire pressure to 26 pounds per square inch, created a
dangerously thin margin of error.
The recalled Wilderness AT tires carry a temperature rating of "C" under the
federal government's Uniform Tire Quality Grading Standards -- the minimum
acceptable government rating. Most SUV tires carry B or A ratings. Consumers
Union recommends tire buyers only consider A- or B-rated tires on any vehicle,
car or truck. A-rated tires can withstand the greatest heat and load.
Under federal standards, a C-rated tire must be able to pass a test that
entails running on a wheel drum at 250 rpm for two hours at 95 degrees, and up
to another four hours at speeds starting at 375 rpm, stepped up to 575 rpm. If
the tire fails before the 500 rpm stage, it gets a C rating. If it makes it to
575 rpm, it gets an A rating. In between, it's a B.
Ford has cited the safety record of 3 million Explorers with Goodyear
Wrangler RT/S tires in model years 1995 through 1997 to point the blame at
Firestone. But those tires all carry a B temperature rating, as do the tires
Goodyear is supplying as replacements in the current Ford recall.
"All of our tires carry a B rating or higher," said Goodyear spokesman Chuck
Sinclair. "We don't supply a C-rated tire."
Ford stopped using Goodyear as a supplier after the 1997 model year because
the supplier could not produce a Wrangler tire for the Explorer using Ford's
specifications at a price Ford was willing to pay.
The temperature ratings were established in 1980 as part of a consumer
information program. The government also established similar standards for
treadwear and traction.
All three grades must be printed on a tire's sidewall, although the average
consumer will need help in deciphering the codes. (One source are tire safety
Web sites like
www.goodyear.com/us/tire_school and
www.gmtiresafety.com.)
Ford spokesman Ken Zino said temperature endurance was not one of the
specifications given to tiremakers for the Explorer. Ford and other automakers
say a tire's temperature rating should be considered in the context of a number
of performance measures, including traction and stopping distance.
Ford also argues that C-rated tires are used by GM, Toyota and Nissan on
vehicles as large or larger than the Explorer.
Since 1999, GM has used one version of Wilderness AT tires, mostly on
Chevrolet Silverado and GMC Sierra big pickup trucks, with a temperature rating
of C.
GM says it has no unusual problems with the tires and that they are
substantially different from the Ford versions.
GM says its specifications and extensive testing system have ensured the
safety of its customers. David Wood, GM's tire engineering group manager, said
the temperature rating was not as significant as some other factors, such as
high speed tests sanctioned by the Society of Automotive Engineers.
"In the development process, it's not a performance criteria we place a lot
of emphasis on," Wood said. "We are satisfied with the Wilderness AT tires on
our vehicles. We have no plans to change them."
Toyota has used Wilderness tires on about 300,000 Tacoma pickups and 4-Runner
SUVs since 1994. All of the 4-Runner Wilderness AT tires carry a B temperature
rating. One of the three sizes used on the Tacoma carries a C rating.
Toyota spokesman John Hansen said the company has closely tracked warranty
claims on the tires since last year's Firestone tire recall. "It's something
we're very tied into. Nothing has happened to make us lose confidence in the
tire," Hansen said.