Many thanks to you all so far for your advice and information. I'm still waiting for Lexus to tell me whether or not the remaining warranty would be affected in any way, obviously non-Lexus wheels would not be covered. I notice that the new S uses 195x65x15 tyres/wheels, I was going to use 205x65x15 but would it be better to use the narrower tyres given, as pointed out, that they are lighter etc? I have an Audi A4 with 195x65x15 tyres and the road holding etc on that is quite satisfactory. With reference to any effect on speedo readings, as these different sizes of wheels/tyres are available as an option, I assumed they cancel each other out ie reduced wheel diameter compensated by increased tyre diameter and vice versa, though from some earlier comments on the forum there could be a difference of up to 2mph. The big downside for changing is cost - Lexus quoted me £1,500 for a set of wheels with tyres whereas Wheelbasealloys quote £634 for an equivelant set.