Ideally, when the car reaches the turn, the driver will steer it along the line marked with green dots. However, if the car is too 'tight', it will understeer, following the red dotted line and leaving the road.Understeer is a term for a car handling condition during cornering in which the circular path of the vehicle's motion is of a markedly greater diameter than the circle indicated by the direction its wheels are pointed. The effect is opposite to that of the oversteer and in simpler words understeer is the condition in which the front tires don't follow the trajectory the driver is trying to impose while taking the corner, instead following a more straight line trajectory.
Physics
Under all high speed (greater than approximately 10mph (15 km/h) for a typical automobile) cornering conditions a wheeled vehicle with pneumatic tires develops a greater lateral (i.e. sideslip) velocity than is indicated by the direction in which the wheels are pointed. The difference between the circle the wheels are currently tracing and the direction in which they are pointed is the slip angle. If the slip angles of the front and rear wheels are equal, the car is in a neutral steering state. If the slip angle of the front wheels exceeds that of the rear, the vehicle is said to be understeering. If the slip angle of the rear wheels exceeds that of the front, the vehicle is said to be oversteering.
Conditions that cause Understeer or Over steer.
As with oversteer, understeer has a variety of sources such as mechanical traction, aerodynamics and suspension.
Classically, understeer happens when the front tires have a loss of traction during a cornering situation, thus causing the front-end of the vehicle to have less mechanical grip and become unable to follow the trajectory in the corner.
In modern race cars, especially open wheel cars, understeering is caused mainly due to the aerodynamic configuration. In this respect, the lack of a heavy aerodynamic load (downforce) in the front side prevents the front tires from gaining enough traction. At the same time understeer can be caused by having a heavier aerodynamic load at the rear end of the car giving the rear tires more traction than the front tires. Also, suspension balance should take into account the types of surfaces being driven - differing levels of friction in each surface influence the potential understeer behavior. Camber angles, ride height, tire pressure and centre of gravity are important factors that determine the understeer/oversteer handling condition.
Understeer covers several different phenomena, in particular, there is a big difference between linear range understeer, typically between 0 and 0.4g, and limit handling understeer, which is at higher lateral accelerations, and is what racing drivers are talking about.
Posted by: Raja Babu Dwivedy.
ID: 4810750499.
Reference: http://en.wikipedia.org/wiki/Understeer
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