When I read car reviews, I see mentions of oversteer and understeer and have no idea what they mean to me as an ordinary driver. Is one good and one bad? Both bad?
Understeer and oversteer are driving characteristics that involve sliding of either the front or rears tires. Excessive understeer and oversteer can result in an out-of-control car. You’ve probably experienced these characteristics on slippery roads, but on dry pavement these traits only reveal themselves when the car is pushed to its handling limits.
A car’s tendency to understeer or oversteer is most commonly attributed to whether it’s front- or rear-wheel drive. Front-wheel-drive cars characteristically understeer, while rear-wheel-drive cars tend to oversteer. Both front- and rear-wheel-drive cars, though, can experience both understeer and oversteer in the right conditions. The more power a car has, the more likely understeer or oversteer will show their faces. Many new cars offer electronic stability control that will kick in and keep the car in control when it starts to slide.
Understeer happens when the front wheels start to plow straight even if you have the steering wheel turned. Front-wheel-drive cars are susceptible to understeer because power is being sent to the same wheels that steer the car, and when the tires start spinning there’s no grip to steer. If your front tire tread has ever been packed with snow or mud, you know the feeling of understeer because, as you turn the wheel, the car keeps going straight.
Oversteer is the tendency for the rear end to slide out or fishtail. In responsible everyday driving, there’s no reason oversteer should be a concern. In rain, snow or mud, however, the rear end of rear-wheel-drive cars can creep out on you. Traction and stability control can minimize that fishtailing. The exhibition sport of drifting is an activity that revolves around oversteer; drivers pitch their specially-built cars sideways and smoke the tires at high speeds.
All-wheel-drive cars aren’t exempt from oversteer and understeer, but can recover more easily because all four wheels are searching for grip.
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The ask.cars.description of understeer and oversteer makes the common mistake of equating these features with sliding or skidding tyres.This is not accurate as these conditions are induced by any difference between the angular deflection of the front tyres in relation to those at the rear.
Those interested may refer to Jan P Norbye's excellent book 'CHASSIS TUNING[Theory and practice of] [Sports Car Press Ltd US/ Speedsport Motorbooks UK].Norbye's book explains better than most how understeer and oversteer have nothing to do with grip,skidding or sliding,nor indeed anything to do with aerodynamic downforce.All of which must come as revelation to followers of the popular media.
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here is a good explanation of understeer:
http://www.drivingfast.net/car_control/understeer.htm