lower profile rubber requires higher psi, higher profile like my 15's require lower psi, ie my 15's I run at 33psi. A set of 18" Quakes for example with 235/45 rubber I run at 40psi. higher profile tyre with lower pressure still has more air in it because of the volume, which is why they give a more comfortable ride. lower profile tyres under higher pressure have less air in them, but they need the higher pressure to maintain rigidity in the side-walls. This combined with less side-wall flex is why low profile tyres corner so nicely

Kyron when did you find out they were cactus? Was it when you went to get the alignment done?
Falconboy101 - where do you live? If you're near Canning Vale then I'd suggest Tyre Power there as they're good at what they do and they're a club sponsor. If you live near Balcatta I'd suggest the Diffen's store there I think just off of Erindale Rd there. Frank the Seth Efrican fella is a good bloke and should look after you.