This refers to the weight not carried by the frame of the car. The less
un-sprung weight you have the better it is for the vehicle. As Jose said
earlier that the larger wheels 12" or 13" rims with the 50 series tires will
look like your riding in a "HOT WHEELS" toy, but will take for ever to get
to cruising speed (un-sprung weight was increased causing substantial power
lose). Lighter wheels will increase performance letting your small one to
even spin your tires for a few feet. There are companies that will make
rims for you, but you have to say up front that they must be lighter than
the original rims or why do it. Also, don't forget the tires, they too add
to the wheel weight. What are the best rim to get, 10" rims with a 5"
width. They will give the reduced weight and open the tread to allow for
better handling.
Bill