When the car begins to slide, the front and rear wheels normally have different angles of slippage. Simply put, it is either the rear or the front wheel which starts skidding first. This result in either the car wanting to continue in a straight line (called understeer) or the rear of the car stepping out of line (called oversteer). Sometimes, slip angles at both the front and the rear are equal and the car attains a condition so – called neutral steer (above centre). Though, this might seem to be an ideal state of balance, in reality a car with mild under steering tendencies is more stable to drive and less nervous than one having neutral steer characteristics.
When an understeered vehicle is taken to its frictional limits where it is no longer possible to increase the lateral acceleration, the vehicle will follow a path with a radius larger than intended. Although the vehicle cannot increase lateral acceleration, it is dynamically stable but when an oversteered vehicle is brought to its frictional limits, it becomes dynamically unstable and has a tendency to spin out. A neutral steered might not spin out in such conditions but it is relatively unstable than an understeered vehicle but better than an oversteered vehicle. Many properties of the vehicle affect the understeer factor which includes the compliance in the steering system, tire cornering stiffness, camber thrust, lateral force compliance steer, self aligning torque and lateral load transfer. These individual contributions could be identified analytically or by measurement in the Bundorf analysis.