Cost yes. But the XX7 and the XU3 where a sports package. gts bits n pieces etc.

XX7 and XU4 both got sedan tyres. So the reason for this is they handle better. The commersial tyres where not as good on the road.

only differance between the XX7 and XU4 is that XX7 got the gts bits aswell. =)

You say you have a XU4. What model is it?