Thanks for your comments chaps
One thing I noticed having done a few miles on them now on a mixture of roads including some 'spririted' driving - the car feels more solid for want of a better word.
Not sure if its the wider track in general, or the fact that me rear is now an additional 15mm more far out than it is as standard on each side, but it feels more composed when turning and less twitchy.
Its hard to explain, but its a more planted feeling, which I guess makes sense because theres a wider spread of the weight, but I didn't expect that small numbers like 30mm/15mm either side would make a difference you could feel. On my previous X5 with 25/15mm I couldn't tell the difference but that had a dodgy steering rack so it was hard to feel anything in the steering.
