Ford Passed Up Chance to Boost Explorer’s Stability
Ford Motor Co., whose Explorer sport-utility vehicles have suffered a rash of rollover crashes linked to tire failures, spurned a chance to significantly improve the stability of the vehicles during a major redesign in the mid-1990s, internal company documents show.
With the new suspension system Ford installed in 1995 and later model Explorers, the auto maker could have lowered the center of gravity of the top-heavy vehicles by lowering the engine height, according to memos by Ford engineers. But the company decided to retain the original engine position, at least partly to hold down redesign costs and preserve profit margins of nearly 40% on the popular Explorer, the documents show.
When the Explorer was introduced in 1990, Ford was concerned enough about its stability that it advised owners to maintain a relatively low tire pressure of 26 pounds per square inch, because softer tires help an out-of-control vehicle to slide rather than tip over. Yet the redesign in the ’95 model year made the Explorer’s center of gravity slightly higher and the stability index--a rough measure of rollover propensity--slightly worse, records show.
Rather than improving the Explorer’s stability, “I think they made it worse,” said Tab Turner, a Little Rock, Ark., attorney who has filed numerous lawsuits against Ford stemming from rollover crashes.
A Ford spokesman acknowledged a small rise in the Explorer’s center of gravity with the ’95 redesign, but said the difference is inconsequential.
And the spokesman, Jon Harmon, said that federal accident statistics show the Explorer has had a lower rate of deaths from rollovers and other crashes than other SUVs of comparable size. “That safety record is no accident,” Harmon said. “Explorer is an extremely well-engineered vehicle.”
SUVs have a safety record similar to passenger cars when all types of crashes are considered. But their risk of rollover is considerably higher, because their high stance and narrow track width make them prone to flip over in severe steering maneuvers or when they “trip” on curbing or other obstacles.
From 1991-99, 1,142 people died in rollover crashes of Explorers, according to data gleaned from the federal Fatality Analysis Reporting System by Randy Whitfield, a Maryland-based safety consultant. The data suggest that only a small percentage of the rollovers were triggered by tire failure.
But the rollover propensity of Explorers and other SUVs has come into focus mainly through the massive recall of Firestone tires that were original equipment on Explorers and some other light trucks.
Federal safety regulators have received hundreds of reports of the tread suddenly peeling off three models of recalled 15-inch Firestones, often when vehicles were traveling at highway speeds. At least 100 deaths in the U.S. and nearly 50 more in Venezuela have been linked to the tread separations, many involving rollover crashes of Explorers.
Although Ford has been adamant that the Firestone tires are solely to blame, auto safety experts say the instability of the vehicles, coupled with bad tires, have made a deadly combination because SUVs are harder to bring under control than passenger cars when their tires fail.
Reports, memos and other documents concerning the design of the Explorer have been produced by Ford in response to discovery demands in dozens of lawsuits stemming from rollover crashes, some involving tire failures and some not.
Documents previously disclosed by The Times show that as the 1990 launch of the Explorer approached, Ford engineers were concerned that the vehicle be at least as stable as the Bronco II compact SUV that the Explorer would soon replace. Ford has settled hundreds of lawsuits stemming from Bronco II rollovers, and an internal memo described those vehicles as being in the “middle to poor” range in rollover risk.
But documents from the late 1980s show that an Explorer prototype had fared worse than Bronco IIs in a set of extreme steering maneuvers on an Arizona test track. The prototype also had a lower stability index, calculated by taking half of the vehicle track width and dividing by the height of its center of gravity.
As a result, documents show, Ford made two changes--lowering the Explorer by half an inch and stiffening the front springs--to improve stability over the Bronco II.
An undated memo stated that some features of the Explorer--particularly its twin I-beam suspension--resulted in a high engine position and prevented “further significant improvement” in stability.
When Explorer production began in early 1990, Ford was already at work on a redesigned version for the ’95 model year. Among the biggest changes: scrapping the twin I-beam in favor of a short-long-arm front suspension, or SLA.
The switch was intended to accommodate two other key changes: use of rack-and-pinion steering and dual air bags, Ford officials say. But the new suspension also made it possible to lower the center of gravity by lowering the position of the engine, a memo said.
But that memo, dated March 26, 1990, said Ford had decided not to exploit the opportunity.
The decision “to retain the . . . engine position minimizes the effect on other vehicle systems . . . but does not take advantage of the fact that the engine could be lowered with a SLA-type suspension,” the memo said.
“This decision was driven by early implementation and program cost.”
Ford officials refused to discuss the expense of changing the engine position, or whether there were other reasons not to do it. Harmon said he believed the engine height actually did go “down by millimeters,” but would not elaborate.
However, other documents discussed the high cost of the redesign and the need to protect the Explorer’s impressive profit margins.
According to a 1991 memo, the Explorer was contributing a profit that year of $559 million. Profit margin on the vehicles was 38.8%, the document said.
In a deposition last spring, Ford executive Mehendra “Max” Kapadia, who had been launch manager for the redesigned Explorer, said he believed the 38.8% profit did not factor in all of the Explorer’s costs, and that the “pure margins are much, much lower.”
The 1991 memo estimated the increased costs of the ’95 redesign at $1,267 per vehicle, despite cost-reduction programs.
According to another document, one of the economies involved using thinner metal panels to construct the Explorer’s roof.
Experts say most vehicle roofs are extremely weak, thanks to a federal roof crush standard that has not been changed for three decades, and was widely regarded as ineffective at the time it was adopted. Safety advocates say the issue is important because a major cause of deaths and paralyzing injuries in rollover crashes is the roof collapsing onto occupants.
However, the Ford memo did not make clear whether the plan to thin the roof of the ’95 Explorer would weaken it. The document signaled an intent to reduce the “gage,” or thickness, of the roof panels “and go to baked hardenable”--a reference to using heat to temper the steel.
Harmon refused to discuss whether the strength of the roof had been lowered.
The National Highway Traffic Safety Administration recently published stability indexes for a wide range of passenger cars and SUVs and other light trucks. According to the list, the original four-door model of the Explorer had a stability index of 1.08, while the index for ’95 and later models dropped to 1.06. Since the width of the vehicle had not changed, the decline meant the center of gravity rose slightly, Ford acknowledged.
But this is “a razor’s distinction,” said Harmon. Ford and other auto makers also maintain that the index is misleading because it does not take account of individual vehicle design features that could increase or decrease rollover risk.
“You can’t make any kind of correlation between a change that small [between the original and ’95 Explorers] and any real-world performance,” he said.
While lowering a vehicle’s center of gravity is one way to increase stability, so is widening its track. Internal memos in 1987 and 1989 show that Ford engineers had suggested widening the stance of the Explorer, but the step was not taken.
More than a decade later, however, the company is heeding that advice. Ford has announced that the 2002 Explorer, due out early next year, will be 2.5 inches wider than the current model.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Determining Rollover Risk
The Ford Explorer redesign in the mid-1990s made its center of gravity slightly higher--and the rollover risk slightly worse, as indicated by the Static Stability Factor.
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Finding Stability Factor
Static Stability Factor equals one-half the tire-track width (t), divided by the height of the center of gravity above the road (h).
SSF Rating
* 1.04 or less: risk of rollover 40% or greater.
** 1.05-1.12: risk of rollover greater than 30% but less than 40%.
*** 1.13-1.24: risk of rollover greater than 20% but less than 30%.
**** 1.25-1.44: risk of rollover greater than 10% but less than 20%.
***** 1.45 or more: risk of rollover less than 10%.
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Selected SSF Comparison (4-wheel drive models)
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Make/model Model year SSF Dodge D-150 Ram 1988-93 1.28 Honda CR-V 1997-98 1.19 Ford F-150 pickup 1988-96 1.15 Chevrolet Astro van 1996-98 1.12 Nissan Pathfinder 1988-98 1.10 Ford Explorer 1991-94 1.07 Ford Explorer 1995-98 1.06 Ford Bronco II 1988-90 1.04
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Source: National Highway Transportation Safety Administration
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