My forth BMW...love the 550i Spt...would not change a thing! My wife on the other hand would prefer to sacrifice a little handling for comfort. I read an article that stated tires contribute 70% to the ride...can we go from the current 245/35/19s and 275/30/19s to a deeper sidewall ratio (245/40 and 275/35 respectively) without too much compromise? The dimensional variation between tire brands leads one to assume there is enough tolerance concerning fitment. Any recommendations based on actual experience or expertise would be greatly appreciated. Thanks.