i got an au2 xr8 ute,it had standard 17's,235/45/17's.With the 17's it rode quite well.tho over bumps it was harsh,due to the stiff suspension. I now got 18's on it,245/40/18, with the narrower sidewalls its much more stiffer and it really hates bumps,even tho its still stock suspension. Tyre prices vary depends what you buy,the factory dunlop sp 9000 are noisey,but very grippy and very expensive, around $450 per tyre for 18'
I bought kumho 712's for the 18's,cost me $280 per tyre,they quiet but not as grippy as the dunlops.
Terrorising a crap driver near you!