DETROIT — The Ford Motor Co. will warn buyers of its sport-utility vehicles and pickup trucks about limits on how much weight they can carry safely in their vehicles.
But the company said that it has not linked overloading to crashes involving Ford Explorer sport utilities equipped with Firestone tires.
The automaker has decided to start including payload information next year on the stickers inside the doorjambs of Ford sport utilities and pickups to "address customer satisfaction," said Jon Harmon, a spokesman for Ford. Ford is drafting new text for future owners' manuals, too, he said.
"Some of the wording in our owners' manuals for trucks and SUVs was written a number of years ago for use primarily by commercial customers, reflecting the tough truck, hard-working heritage of our vehicles," Harmon said in a short statement on Monday. "Now that so many of our trucks and SUVs are used by individuals and families as personal transportation, it's time to update the payload instructions."
The doorjamb stickers currently tell owners the maximum recommended weight of their vehicle when fully loaded, but not how much the vehicle weighs when empty. That makes it hard for owners to calculate how many people and how much luggage and other cargo may be placed safely inside. A vehicle's payload is the difference between its weight when fully loaded and its weight when empty.
The owner's manual for the Explorer suggests that owners weigh their vehicles for themselves: "To obtain correct weights, try taking your vehicle to a shipping company or an inspection station for trucks," the manual for the 2000 Explorer says.
States commonly discourage people from weighing their vehicles at highway weigh stations, which exist to enforce regulations limiting the weight of commercial trucks. Lt. Jamie Mills of the New York State Police suggested that sport utility owners who want to weigh their vehicles should head for the scales at the nearest municipal garbage dump.
Extensive government tests have found that sport utility vehicles are more prone to rolling over when heavily loaded, because the seats and cargo area are above the vehicles' centers of gravity. The stability of cars and minivans is less affected when they are full of people or belongings, because seated occupants and luggage in the trunk are located roughly at the same level as the centers of gravity for both cars and minivans.
Harmon said that Ford was making the change in response to inquiries from The New York Times about the adequacy of the current manuals, and not because of any concerns that overloading had caused the crashes in Explorers equipped with Firestone tires.
"It wasn't as clear as it could be, as you pointed out — this wasn't a safety issue," Harmon said.
Regulators have received complaints linking Firestone tires to 119 deaths, mostly in Ford Explorers that rolled over. But the complaints do not provide enough information to determine how heavily laden the vehicles were when they crashed. The federal government's database on fatal crashes nationwide also does not provide this information. Lawyers who are suing Ford and Firestone said that while some crashes had involved overloaded vehicles, others had not, leaving no clear pattern.
Bridgestone/Firestone has been working to complete the recall of 6.5 million Firestone brand tires that may be prone to come apart under certain conditions, and which have been blamed for dozens of fatal crashes. The tires recalled were installed mostly on Ford Explorer SUVs and pickup trucks. Bridgestone/Firestone Inc., a unit of the Bridgestone Corp. of Japan, said Monday that it had replaced 4.8 million of the 6.5 million tires it recalled on Aug. 9.
Greer Tidwell, a Firestone manufacturing director involved in the tire maker's investigation of what went wrong, said that as the weight on a tire increases, the tire becomes hotter and more likely to fail. Firestone has found in tests that the left-rear tires on Ford Explorers become hottest of all during routine driving, he said. Failures of left-rear tires have caused more of the Explorer crashes than failures of tires in any other position.
But Firestone has not tried to determine the weight inside the Explorers that crashed, nor is it clear whether weight or temperature caused the tire failures, Tidwell said.
David Champion, the director of auto testing at Consumers Union, the nonprofit group that publishes Consumer Reports magazine and has long complained about the limited payloads of sport utilities, said that overloading could be a safety issue because of the rollover problem. Consumers should also be aware that many sport utilities are not able to carry as much weight safely as cars or minivans, even though the large cargo areas of sport utilities might tempt customers to fill them, he said.
The Explorer has one of the most voluminous cargo areas of any mid-sized sport utility vehicle, but little, if any, extra capacity to carry weight, making it particularly easy to overload an Explorer, Champion said.