Running 245/45/18 and 235/40/18 on the front no problems whats so ever. Ive done more than 20k miles on them too. Im replacing them for 225/40/18s as they are a hell of a lot cheaper. I personally havent found any of this traction control problems alot of people bang on about. Maybe my car is different?
Clearly you've never understoon any of the posts I've made explaining how TC works then? You are not finding any problem as your difference in percentage terms of rolling radius front to rear keeps the stagger that the TCS expects. Should you run tyres with the same rolling radius front to rear you will understand what we are talking about.
As for the OPs original question, yes you can run a 40 profile. I did on my 18s on the 350z as Falkens have somewhat soggy sidewalls and I was recommended to do so. You need to keep the OEM front to rear stagger in rolling radius though. So use 40 profile all round and you'll be fine AFAIK, but keep to staggered widths such as 225F and 245R.
Thanks for the info
On the point that the miles will rack up faster, how much difference are we talking?
E.g. for every ten miles on the odometer, the smaller profile tyres will only travel XX miles.