I think John was championing the idea of using Michelin XVS 185 section tyres on 6" rims rather than on the standard 5" rims. Michelin specifies their 185 tyres will fit on 5", 5.5" and 6" rims. You do not get any extra tread on the road but stretching the tyre sideways tends to stiffen the side walls which can have a positive effect on handling. The downside may be a loss of ride comfort due to loss of compliance in the side walls but I doubt you would notice - although my wife probably would :? . Using this combination improves the front/rear aspect of the car while retaining the side on view of full wheel arches. The downside of lower profile tyres (apart from a reduction in ride height) is the car looks odd from the side.
185 section tyres on 5" wheels:
So the ideal world Mark - ditch those time expired 225 Pirelli's and put on a set of 185's :D