OVERSTEER/UNDERSTEER: When discussing a vehicle's handling characteristics, the words "oversteer" and "understeer" keep cropping up. For some they represent the thrill of the driving experience, for others they put the fear of God into a driver.
Oversteer: The vehicle wants to turn too far, with the back end sliding around and, in extreme cases, trying to pass the front. An oversteering vehicle feels like it's about to spin, and frequently does if the driver does not make adjustments in time.
Understeer: A vehicle doesn't turn as quickly as the angle of the front wheels suggests. Turning the steering wheel further just makes the tyres slip more. An understeering vehicle wants to point to the outside of a turn, ploughing ahead instead of where the wheels are aimed.
A good way of understanding it is with understeer, you see what you're about to hit through the windscreen - with oversteer you see it in the mirrors.
Most cars have a bias towards understeer as it's thought that understeer is easier for the average driver to cope with than oversteer.
The instinctive reaction for a driver in a sliding car is to lift off the throttle and hit the brakes, which will transfer weight to the front end and increase traction there, helping an understeering car to recover control.
Doing the same thing in a car that's oversteering will usually make the situation worse by unloading the rear tyres and further reducing traction.
It's possible for a vehicle to exhibit both understeer and oversteer at different times.
For example, the first-generation Porsche 911 Turbo had the weight of the engine over the back axle, a big tyre size difference front-to-rear, and an engine that produces a sudden hit of power from the turbo.
It was notorious for evil handling characteristics, going from power-off understeer to power-on oversteer.
Porsche has managed to breed these traits out of the newer 911s through careful chassis tuning, redistribution of weight, and the adoption of all-wheel-drive.