As above I'm getting rid of my run flats and am looking at buying 205/40/17 Yokohama prada spec 2 tires, will changing to a 40 profile be a good idea? I'm not to fussed on comfort and will lowered on 40 mm springs cheers

 

A 40 series will still leave a lot of wheel gap. 205/45-17 will fill the wheel gap and give you a better ride.

 

Agreed. Either stay with the stock 205/45 or go to a 215/40.