Lift-off oversteer (also known as snap-oversteer, trailing-throttle oversteer, throttle off oversteer, or lift-throttle oversteer) is a form of oversteer in an automobile that occurs when the vertical load on the tires shifts from the rear to the front quickly due to throttle release while cornering. This decrease in vertical load causes a decrease in the lateral force generated by the rear axle, so the axle starts to accelerate towards the outside of the turn. This steers the car more tightly into the turn, hence causing oversteer. In essence, this means that easing off the gas causes the rear wheels to break away suddenly, with the potential for the car to leave the road tail first.
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This type of oversteer is often more pronounced in rear-engined cars and cars with swing axle rear suspension. Rearward centers of gravity (such as older Porsche 911s) enhance this effect, though technically any vehicle can experience lift-off oversteer. Various suspension enhancements, such as a Weissach axle, Passive rear wheel steering, or a multi-link suspension, can limit a vehicle's tendency to oversteer in this situation. Even the handling of the Chevrolet Corvair improved in final years of production through the use of enhanced anti-roll bars, according to John DeLorean's book, On a Clear Day You Can See General Motors.
The graphs to the right show the simulated effect of lifting off the throttle in the middle of a left turn. The transients in the first couple of seconds are due to the test, in which a step steer input (wheel angle) is applied at 0 s and held constant throughout. The steady state cornering is at constant speed, with a lateral acceleration of 0.45 g approximately until the throttle is released at 6 s.
The yaw rate plot shows the oversteer due to the rear wheels losing traction - after an uncomfortable jerk at 20 deg/s, the vehicle spins sharply in the direction of the turn. The lateral acceleration also spikes to 0.6 g and levels at about 0.55 g, meaning that the radius decreased (i.e., the turn tightened). The side forces on the outside wheels increase and the inside rear (LR) wheel even lifts off the ground, a common occurrence.
In the 1940s, the Nazis described the Tatra automobile as the Czech Secret Weapon due to its treacherous and deadly lift-off oversteer handling characteristics.
Attorney and consumer protection activist Ralph Nader described this type of handling in his 1965 book Unsafe at Any Speed
On April 10, 2010, Consumer Reports magazine rated the 2010 Lexus GX 460 SUV a "Don’t Buy: Safety Risk." A panel of four automotive test engineers determined that the vehicle was subject to excessive lift-off oversteer during a standardized evaluation for emergency handling. The test simulates scenarios such as transiting a highway exit ramp while traveling with excessive speed.[1] On April 19, Toyota recalled the GX 460 and the Toyota Land Cruiser Prado for a software update to the electronic stability control to correct the issue.[2]
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