looking at most 18" wheels around 14kg... the speedlien do one 18" for around 7.5kg ... what difference will this actually make?

reduction in unsprung mass. Means suspension behaves better, ride improves and handling.

Extra weight on the wheels has to be accelerated in the rotation as well as with the rest of the car so it has a greater effect than adding the extra weight to any other part of the car.

So get a light wheel and tyre package and the car will handle better.
Whats the weight of the standard 16' wheel and tyre on the 99-00my ?
If you want the car to handle better match the weight or go lighter package?

bc, yes lighter means better - in theory! Trouble is, lower profile tyres also improve handling, for which you need bigger wheels, which are almost always heavier. Also, the suspension has to match the wheel/tyre combination.

The OEM 16in wheels and tyres weigh approx 18kg. Add another 3kg for 17in, on average.

Richard.

nice one hoppy

OZ Superleggeras are really really light in 17"

Can't remember the exact weight, but they are massively lighter than the OEM 16"s on an MY00

They also look the mutts IMHO