Quote Originally Posted by Mjolinor View Post

I will probably change mine for steels this week as I have a set ready to go on, I will know then what difference it makes to a Smart car.
But only if the same tyres at the same pressures are fitted to wheels of the same width (to preserve sidewall angle to tread). The remaining variable (volume of air) may impact on the result if sufficiently different (though I'd expect them to be similar given the requirement for a void into which a deflated tyre can retreat rather than be thrown).