well i find running the smaller rims (13") with larger side walls that my car drives a little like a boat and sort of sways a little bit in the rear end and when your tearing through windy roads in the hills at 100k's thats not the best feeling. the 15's handle much better and offer less understeer, with my driving style. so im not saying that this is the way to go for everyone, its just what works for me.