I have a 2005 BMW 535d M Sport Touring fitted with standard run-flats that give a hard and uncompromising ride. I'm swapping them round with a view to wearing them evenly so I can change to standard tyres, and buy a space-saver wheel kit from BMW for about £180. Trouble is I'm getting mixed messages from tyre suppliers and garages. One school of thought seems to be that the change transforms the car for the better in terms of ride and handling, while the other advises sticking to the run-flats as BMW designed and set the vehicle up specifically for these. I would like to change, not least because of the greater choice and cheaper price of standard tyres, also because run-flats have to be written off after a puncture. I can live with the prospect of a roadside tyre change if it happens, and really don't hold with the argument that a space-saver adds significant weight to a large car like this. I'd appreciate your views.