Polar moment of inertia

A very important concept related to the maneuverability, which dictate the availability of a car to change direction is named polar moment of inertia.

“The poles of inertia” is another way of saying “mass concentration centers”. “Moment”, this concept is determined by position on the longitudinal axis (front and back) of the center of gravity. The car changed its direction around own center of gravity in a turn and with more distance between the centers of concentration of mass in relation to the center of gravity of the automobile (which is common center of gravity), then the moment will be more significant.


A high polar moment of inertia is present when mass concentrations are bigger and very far from the center of gravity.
Low polar moments of inertia are present when the concentrations of masses are small and very close.
In other words, a car with a low polar moment of inertia will be easier to change its direction and at high polar moment of inertia the mass is concentrated near the CoG (center of gravity), that´s the case with all/most mid-engined sports/race cars and this leads to an very nimble handling, easy to change direction, however it also results in more rapid ‘break away’ and loss of control at a higher cornering speed.


A car with a low polar moment of inertia will respond quickly to steering commands. A car with a high polar moment of inertia will have higher directional stability (ie, it will oppose more to changes of direction).

Polar moment of inertia was last modified: December 8th, 2015 by Le Crow