Re: unsprung weight? (tmac)
A Simple answer is...
Sprung weight, is the weight of all items supported by the springs,, ie, most of the car,
Unsprung weight is the weight of those items that are essentially supported directly by the road via the tires before you get to the springs. Such as the tires, the wheels, the hubs, the discs, maybe the back axel. (essentially the weight of the suspension pieces & brakes)
There are a few items that are more ambiguous, because they have a connection to a supported location, and a connection to an unsprung object. Things like half shafts, suspension arms, shocks, and steering arms.
most likely the weight of these items is split between sprung/unsprung categories.
For normal suspension purposes, it is probably easier to achieve better ride quality if the weight of those components is reduced.
On some jaguars, and a few other older english cars, they actually moved the rear discs next to the differential, so they could reduce the weight of the rear suspension.