Look @ World Rally for the tire concept. In snow and ice they rock tall, narrow tires. I live in Tahoe and when there is wet loose snow often and it can be hairy sometimes. The principle is simple. The smaller contact patch can bite better, and is less prone to floating. The tire will bite and direct its load to the hardest part of the snow, often underneath the loose stuff. It also can focus the bite on ice, especially with studs. Wide tires hydroplane in snow, and also bite less because of the surface area. WRC cars run wide, thin tires on aspahalt(no flex), and on dirt gravel run 'fat tires' on smaller rims(more flex), and on snow the tall narrow as I mentioned before. If you live in hardcore snow environment, I suggest winter setup w/ studs, and a summer package, for asphalt or whayever you run which is ideal. I don't myself but I don't think it is neccessary for me-