Most of a cars weight is supported by its suspension. It suspends the body and associated parts so that they are insulated from road shocks and vibrations that would otherwise be transmitted to the passengers and the vehicle itself.
However, other parts of a car are not supported by the suspension, such as the wheels, tyres, brakes and steering and suspension parts not supported by springs. These parts are all called unsprung weight. Generally, unsprung weight should be kept to a minimun.
thanks lee. now can u tell me how much 1kg less unsprung weight would equal in sprung weight? LOL :P