Quote:
Originally Posted by s_t
A wheels weight distribution is a good point; one that is rarely mentioned. It will determine the torque required to achieve a particular rotational acceleration. However it is calculated using the Moment of Inertia - no need to go polar for this  Weight closer to the axis of rotation will have less impact on rotational momentum than the same weight further out. |
Polar Moment of Inertia is a metric used by the Society of Automotive Engineers in their standard practice for all components of rotational mass.
Coastdown testing of vehicles cannot be accomplished without a full accounting of polar moment of inertia for all rotating components of the drivetrain.
It's just an engineering convention.