Automobile Handling - Cars With Unusual Handling Problems

Cars With Unusual Handling Problems

Certain vehicles can be involved in a disproportionate share of single-vehicle accidents; their handling characteristics may play a role:

• Early Porsche 911s — suffered from treacherous lift off oversteer (where the rear of the car loses grip as the driver lifts off the accelerator); also the inside front wheel leaves the road during hard cornering on dry pavement, causing increasing understeer. The roll bar stiffness at the front is set to compensate for the rear-heaviness and gives neutral handling in ordinary driving. This compensation starts to give out when the wheel lifts. A skilled driver can use the 911's other features to his/her advantage, making the 911 an extremely capable sports car in expert hands. Later 911s have had increasingly sophisticated rear suspensions and larger rear tires, eliminating these problems.
• Triumph TR2, and TR3 — began to oversteer more suddenly when their inside rear wheel lifted.
• Volkswagen Beetle — (original Beetle) senstitivity to crosswinds, due to the lightness of the front of the rear engine car; and poor roll stability due to the swing axle suspension. People who drove them hard fitted reversed wheels and bigger rear tires and rims to ameliorate.
• Chevrolet Corvair - cited for dangerous handling in Unsafe at Any Speed caused by poor roll stability due to the swing axle rear suspension similar to that used in the Volkswagen Beetle. These problems were corrected with the redesign of the Corvair for 1965, however, it died from its negative publicity.
• The large, rear-engine Tatra 87 (known as the 'Czech secret weapon') killed so many Nazi officers during World War II that the German Army eventually forbade its officers from driving the Tatra.
• Some 1950s American "full size" cars responded very slowly to steering changes because of their very large angular inertia, softly tuned suspension which made ride quality a priority over cornering, and comfort oriented cross bias tires. Auto Motor und Sport reported on one of these that they lacked the courage to test it for top speed, probably due to their familiarity with smaller European cars and their unfamiliarity with large American cars.
• Dodge Omni and Plymouth Horizon — these early American responses to the Volkswagen Rabbit were found "unacceptable" in their initial testing by Consumer Reports, due to an observed tendency to display an uncontrollable oscillating yaw from side to side under certain steering inputs. While Chrysler's denials of this behaviour were countered by a persistent trickle of independent reports of this behaviour, production of the cars was altered to equip them with both a lighter weight steering wheel and a steering damper, and no further reports of this problem were heard.
• The Suzuki Samurai — was similarly reported by Consumer Reports to exhibit a propensity to tipping over onto two wheels, to the point where Consumer Reports claimed they were afraid to continue testing the vehicle without the attachment of outrigger wheels to catch it from completely rolling over. In its first set of tests, the Samurai performed well. R. David Little, Consumers Union's technical director, drove the light SUV through several short, hard turns, designed to simulate an emergency, such as trying to avoid a child running in front of the car. An article published several years later in a Consumer Reports anniversary issue prompted Suzuki to sue. The suit was based on the perception that Consumer Reports rigged the results: "This case is about lying and cheating by Consumers Union for its own financial motives," George F. Ball, Suzuki's managing counsel, said Monday. "They were in debt, and they needed a blockbuster story to raise and solicit funds." Entrepreneur Magazine reported that "Suzuki's case centered on a change CU made while testing the vehicle. After the Samurai and other SUVs completed the standard course without threatening to roll over, CU altered the course to make the turns more abrupt. The other vehicles didn't show a problem, but the Samurai tipped up and would have rolled over but for outriggers set up to prevent that outcome" After eight years in court the parties consented to a settlement which did not include monetary damages nor a retraction. Commenting on the settlement, Consumer Union said,"Consumers Union also says in the agreement that it "never intended to imply that the Samurai easily rolls over in routine driving conditions." CU Vice President of Technical Policy further stated: "There is no apology. "We stand fully behind our testing and rating of the Samurai." In a joint press statement Suzuki recognized "CU’s stated commitment for objective and unbiased testing and reporting."

• Mercedes-Benz A-Class — a tall car with a high center of gravity; early models showed excessive body roll during sharp swerving manoeuvres and rolled over, most particularly during the Swedish moose test. This was later corrected using Electronic Stability Control and retrofitted at great expense to earlier cars.
• Ford Explorer — a dangerous tendency to blow a rear tire and flip over. Ford had constructed a vehicle with a high center of gravity - the tendency to roll over on sharp changes in direction is built in to the vehicle. Ford attempted to counteract the forces of nature by specifying lower than optimum pressures in the tires in order to induce them to lose traction and slide under sideways forces rather than to grip and force the vehicle to roll over. For reasons that were never entirely clear, tires from one factory tended to blow out when under inflated, these vehicles then rolled over, which led to a spate of well publicized single-vehicle accidents.

Ford and Firestone, the makers of the tires, pointed fingers at each other, with the final blame being assigned to quality control practices at a Firestone plant which was undergoing a strike. Tires from a different Firestone plant were not associated with this problem. An internal document dated 1989 states

Engineering has recommended use of tire pressures below maximum allowable inflation levels for all UN46 tires. As described previously, the reduced tire pressures increase understeer and reduce maximum cornering capacity (both 'stabilising' influences). This practice has been used routinely in heavy duty pick-up truck and car station wagon applications to assure adequate understeer under all loading conditions. Nissan (Pathfinder), Toyota, Chevrolet, and Dodge also reduce tire pressures for selected applications. While we cannot be sure of their reasons, similarities in vehicle loading suggest that maintaining a minimal level of understeer under rear-loaded conditions may be the compelling factor.

This contributed to build-up of heat and tire deterioration under sustained high speed use, and eventual failure of the most highly stressed tire. Of course, the possibility that slightly substandard tire construction and slightly higher than average tire stress, neither of which would be problematic in themselves, would in combination result in tire failure is quite likely. The controversy continues without unequivocal conclusions, but it also brought public attention to a generally high incidence of rollover accidents involving SUVs, which the manufacturers continue to address in various ways. A subsequent NHTSA investigation of real world accident data showed that the SUVs in question were no more likely to roll over than any other SUV, after a tread separation.

• The Jensen GT (hatchback coupe) — was introduced in attempt to broaden the sales base of the Jensen Healey, which had up to that time been a roadster or convertible. Its road test report in Motor Magazine and a very similar one, soon after, in Road & Track concluded that it was no longer fun enough to drive to be worth that much money. They blamed it on minor suspension changes. Much more likely, the change in weight distribution was at fault. The Jensen Healey was a rather low and wide fairly expensive sports car, but the specifications of its suspension were not particularly impressive, having a solid rear axle. Unlike the AC Ace, with its double transverse leaf rear suspension and aluminium body, the Jensen Healey could not stand the weight of that high up metal and glass and still earn a premium price for its handling. The changes also included a cast iron exhaust manifold replacing the aluminium one, probably to partly balance the high and far back weight of the top. The factory building was used to build multi-tub truck frames.
• The rear engined Renault Dauphine earned in Spain the sobriquet of the "widow's car", due to its bad handling.
• Three-wheeled cars/vehicles have unique handling issues, especially considering whether the single wheel is at the front or back. (Motorcycles with sidecars; another matter.) Buckminster Fuller's Dymaxion car caused a sensation, but ignorance of the problems of rear-wheel-steering led to a fatal crash that destroyed its reputation.