I was always taught that one of the best ways to increase drive quality and road-holding was to reduce unsprung weight, which was why the majority of British motorcycles had the business end of suspension units at the top. I certainly noticed the difference when I took the run-flats off my current car, and now carry a space-saver. (I don't know what weight-saving I have made overall, if any, but those run-flats were heavy. The run-flat components and thicker sidewall tyres must be a weight alone.)