964 RS mags, how much do they weigh?

The euro 964 RS has 7,5+9x17 Cup design wheels made of magnesium. Does anybody know the weight of these and/or the ordinary cast aluminium ones? Paul Frere says that the weight saving for a set is about 11 kg
(about 24,2 lb), so I guess even having the information about the aluminium ones will help to estimate...

Also, could somebody give a quick briefing about unsprung weight. Is it really true, that unsprung weight is four times heavier than the same amount of normal, "sprung" weight?

Thanks, Mika

Check out the latest issue of 911&PorscheWorld. Running reporters Jack and Cynthia (993 4S owners from the US) talks about unsprung weight, rims and handling. As far as I can remember it's correct that unsprung weight is 4 times "heavier". But you don't need Magnesium rims to loose weight. Go for FORGED aluminum rims (same as the the good old Fuchs). Forged wheels weigh less than cast wheels and in addition they are stronger. Of course there's also Porsches hollow spoke wheels which I believe are cast, but still very leightweight. I'd love a set of wheels from a 993 Turbo.

Thanks for your reply Mikkel,

I really should have been a bit more spesific in my question. As it happens, it was the very same running report you referred to that made me curious about a formula to estimate the effects of unsprung weight. So what I´m really after is a sort of "scientific" explanation about unsprung weight.

The point you made about heaviness of cast wheels compared to forged ones is generally true, but Porsche seems to be able to produce very light cast wheels too!
7x16 Fuchs and 7,5x17 factory 993 CAST alloys weigh the same! That´s why I´m still very interested to find out the weights of the mag wheels or the equivalent factory cast aluminium ones.

Mika