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A condition in high speed driving, lift-throttle oversteer occurs when entering a corner at high speed, the driver lifts the throttle, probably because he's scared himself. A moment later he's postively terrified as the rear wheels break loose and and the whole rear-end swings around on him. Spins are very likely. Why is this?

Lift throttle oversteer is a property of weight transfer. When a car is under throttle, inertia transfers weight to the rear wheels. This is not a problem, although the rear wheels do not steer, they do help hold the car in a turn. When the throttle is lifted, weight transfers forward to the front wheels, giving them more 'bite'. At the same time weight transfers off the rear wheels. This shrinks the contact patch, causing them to lose grip. And herein lies the problem.

What happens that when a car is driven at the limit, is that the rear wheels 'stabilize' the line. But they were already losing all available grip. The tire is out of slip angle. Now it loses all 'grip' and has only friction to do it's work. Which isn't enough. At the same time the front tires bite hard. So the rear end comes around, often so quickly that even talented professionals can't catch it.

For most of us, lift throttle oversteer isn't a problem. First of all, it won't bite you unless you're driving at or near the limit. At reasonable street speeds, all cars have sufficent traction reserve to make the corner. Second, not all cars suffer from a lift throttle oversteer. Most rear wheel drive cars do not, particularly with an open or limited slip differential. Lifting during a corner merely helps the car tuck in tighter, though it does cost you time. Cars that suffer from lift throttle oversteer tend to have a very loose handling, and are often mid or rear engined. Famous examples of cars with significant lift throttle problems are the Porsche 911 and the second generation Toyota MR-2.

If you watch Porsches in road racing you can see how this characteristic changes how the cars are driven. A racing 911 will brake much earlier than a BMW or Viper, so that he is off the brakes before he enters the turn. The Porsche will then power through the turn, out of respect to his car's one major handling vice.

Thanks to Ashley Pomeroy for informing me that in the UK, LTOS is called "lift-off oversteer". Which might be more descriptive as it includes the word off.

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