jeff- as for 18's i would recommend you use the stock size 18's or the next narrow size available.
ideally to get max traction in snow it's better to use the narrowest you can fit so that it digs into ice. but most roads (unless you are in mountains) the streets are plowed and the most you might drive is like 4inches... so the wide tires will do fine, i thinks and just looks so much better.
