I would go with MadMatt's recommendation on the factory size. Personal experiences suggest that the "ugliest" tread design will have the best performance. Lots of curves and/or long unbroken channels running down the center of the tread perform poorly on snow/ice. The first number is tire width. The second number is height. The height (second number) is a ratio of width meaning, the wider the tire, the lower the second number should be to compensate. Remember that tires are an engineered apart of the suspension system. Taller tires tend create a smoother ride at the expense of some responsiveness, handling. Shorter tires tend to give you better response, handling at the expense of a harder/stiffer ride. Wider tires may give you better traction on dry pavement. Narrow tires circumstantially, may perform better in precipitous weather such as snow; wider tires behaving like snow shoes, spreading the vehicle's weight out over a wider surface area. (want the tire to dig-in) In terms of passenger vehicles, the smaller the wheel, the less options you'll find in performance tires.