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Rumble Seat


It's taken longer than I expected for someone to formally implicate Ford Motor Co. in the reign of accidents and death associated with bad Firestone tires. Last week Venezuela's consumer protection agency, Indecu, charged that the accidents that have taken almost 50 lives in that country were the result of a deadly alchemy between Firestone's Wilderness tires and the Ford's Explorer design.

Among Indecu's assertions, it claims that Ford knew the Explorer's suspension was over-soft, making the top-heavy vehicle prone to rollover in a crash or accident. Ford apparently had offered complaining customers in Venezuela sets of stiffer shocks, though the company claims this was done for aesthetic reasons. Stiffer shocks, by the way, are also shorter shocks, which would have the effect of lowering the vehicle onto its wheels, a kind of low-rider effect. Ford's explanation is thus at least plausible, if not particularly compelling.

Indecu also claims that because of the vehicle's squishy suspension--good for ride quality but bad for handling and stability--Ford advised the tires be underinflated, to 28 psi, compared to the Firestone's recommended 32 psi.

A couple of things about Indecu's complaint strike me as odd. First roll-stiffness--the quality of a vehicle to resist the body heeling over--is at least as much a matter of spring stiffness as shock stiffness, though shocks are much cheaper to replace. In other words, new shocks wouldn't get the whole job done. Ford engineers know this.

Another thing: Apparently, the goal of reducing tire pressure is to provide additional sidewall compliance to the softly sprung vehicles, so that in a dramatic turning event such as an emergency avoidance maneuver--the vehicle would be less likely to trip itself. I am not clear about the vehicle dynamics of this. Seems to me a harder tire with a hard, high-mileage rubber compound would be less likely to fold under the Explorer's toppling weight. But tires are strange and wondrous bits of engineering. I'd welcome some enlightenment on this issue.

In the United States, the National Traffic Highway Safety Administration's investigation into tire-failure accidents may yet lead to an indictment of the Ford Explorer.

Yet everyone with a semester of physics under his or her belt understands the situation with the Explorer. Sport-utility vehicles are inherently less stable than cars in emergency maneuvers. Indeed, a high-speed blowout is a worst-case scenario for an SUV: Suddenly, the vehicle stumbles on the blown tire. The weight of the vehicle, situated high over the wheels, is thrown awkwardly in one direction or another. Most SUVs are tuned for on-road comfort, meaning that their limber suspensions would compress easily as the lateral loads of the skidding vehicle increased. The driver, startled, may over-correct, slam on the brakes, or both. Once a sport-utility gets sideways, it's very easy for them to roll over.

Cars and station wagons, for the most part, are very unlikely to roll unless they are tripped--that is, they hit an obstacle like a curb or encounter a sharp change in grade--while they are sliding.

For years, manufacturers have been using self-indemnifying labels on the visors of SUVs, telling drivers to be wary of the vehicle's top-heavy dynamics. The Ford Explorer, the best-selling SUV on the planet, is probably no better or worse than most SUVs based on truck chassis. These vehicles typically weigh in excess of 4,000 pounds, an ungainly amount of weight on such a short wheelbase design.

The current crop of "hybrid" SUVs--including the BMW X5, the Lexus RX300 and the new Acura MDX--all attempt to give buyers the high seating position they crave and some modicum of all-wheel-drive capability, while at the same time being more stable than previous generations of utes. The price of these vehicles should give you some idea of the engineering required to make an SUV keep its feet on the ground.

I am not opposed to SUVs for people who need them. My friend Charles kayaks and hikes, and his life requires the off-road capability of his Mitsubishi Montero. If I needed an SUV in my life, I wouldn't hesitate to buy one. This is America, after all.

But it's just plain crazy that the vast majority--more than 90 percent--of these vehicles are used solely as commuting vehicles. Their liabilities are plain: They pollute more (though Ford, to its credit, has said it will hold all its SUVs to the higher, car-emission standards in the coming year); they burn far more gas in their eight-cylinder engines; they are difficult to see around in, their size complicating both passing and parking; and, for all their bulk, they typically carry no more than a mid-size station wagon.

And finally, they are simply not as safe as cars: They do not stop nearly so quickly as cars, nor do they handle and respond in emergency maneuvers. People who think, Oh, I'm driving a big vehicle, I'm safe, are wrong, maybe dead wrong.

The Explorer issue is just getting started, and its consequences, I predict, will include a general reassessment of these vehicles in our lives. In fact, I expect that in 10 years, the SUV will be passé. Not just passé, but tragically unhip, the vehicular equivalent to men's pony tails and tight shirts.

You needn't dig that far into SUVs to find an unsettling cultural symbolism. They are wasteful, extravagant, anti-utilitarian and dangerously misguided. How much are we like them?

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