Firstly, we will define the effective curve radius as the intersection of the normal angles to the drift angles of the external front and rear wheels.
UNDERSTEERING
When the drift angle of the front tyres is bigger than the drift angle
of the rear tyres, we have understeering. Simply, the grip of the car front
tyres is insufficient, and the car nose points outside the curve. If we
continue at the current speed, the car will slip out the curve. The effective
curve radius will increase.
Usually, the first thing driver does when he notices understeer is
to increase the steering by turning more. Totally wrong! A tyre that has
altready high drift angle will lose more grip when turned more towards
the curve apex. Therefore, the understeer will increase.
We can also brake, which will reduce speed and consequently increase
the grip, but usually we will lose precious time as well as the tyre will
lock due to the blocking of its motion.
The right solution is to deaccelerate withou braking and turn the steering
wheel a little bit to the opposite side. This will reduce somewhat the
understeer and will not lose too much time, as the curve radius will reduce.
OVERSTEERING
When the drift angle of the front tyres is lower than the drift angle
of the rear tyres, we have oversteering. Simply, the grip of the car rear
tyres is insufficient, and the car nose turns more towards the curve apex.
If we continue at the current speed, the car will cross and reverse. The
effective curve radius will decrease.
When a driver notices oversteering, its natural reaction is to brake.
This will surely lock the rear wheels and the car will turn around itself,
or cross. He can also deaccelerate and steer somewhat opposite to the curve.
The loss of speed will reduce the slipping of the rear tyres but the car
will lose much time.
The adequate solution is to accelerate turning opposite to the curve.
Although the grip will be reduced, the car direction will be opposed to
real car motion direction and the traction of the rear tyres will get the
car out of oversteer.
FACTORS THAT AFFECT CAR BEHAVIOUR
| INCREASES UNDERSTEERING | INCREASES OVERSTEERING |
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