CAN ANYONE EXPLAIN ME WHAT IS TURNING RADIUS ??????

@Vinay - to put it simply, the turning radius depends on the ackerman angle, which in turn depends on the distance between the front and rear axles, which in turn is roughly proportional to the vehicle's overall length (longer vehicles have a greater distance between the fron and rear axles). Clear enough?

Centre of gravity affects handling and this is more a function of the vehicle's weight and its vertical distribution rather than the length. Yes, as far as possible both the front and rear wheel pairs must have the equal weight over them - this is rarely the case.

Turning radius of of a vehicle is the radius of the circle traced by the centre of mass of vehicle when steering wheel has been put to extreme right or left. Vehicle having longer wheel base (centre to centre distance between front and rear wheel) have large turning radius and so its very difficult to park thme in limited spaces.

TCD or Turning Circle Diameter is the diameter of Circle made by the centre of the outermost wheel of vehicle while the steering is turned to its maximum possible position.

To measure the TCD of any vehicle (car, SUV, CV, Bus), bring the vehicle at a Plain Concrete or Tar road surface. Take a measuring tape of sufficient length (say 10 m). Take few chalks. You need atleast two persons to do the job.

Turn the steering wheel to the maximum lock position and drive the vehicle in a circle. Simultaneously the other person have to mark (with chalk) the centre trajectory of the outer front wheel at several places. When a circle is completed, take out the vehicle from that circle and measure the diameter of circle at several places. Average of those measurements is the TCD.

Now turn the vehicle in other direction and measure the TCD in same manner. In this way you can measure various TCD and calculate the average.

In better way, you can use the liquid colour on outermost wheel and turn the vehicle in a circle keeping the steering wheel at its maximum lock position. Then measure the Outer diameter (D) of the trajectory of outermost wheel. Measure the width of wheel (W). In this case the TCD will be D - W.

TCD depends on the wheel base, front track and the maximum angle up to which the front wheels can be turned. These things have many design constraints. Lower TCD will help you better manurability in crowded city roads and while parking and also in U-Turns etc, provided the front overhang of vehicle is also small.