I bought 18 inch rims all the way around. They then mounted Blizzaks on all four rims - but taller ones in the rear. You could mount blizzaks on your existing rims, but then you would have to remove them in the spring. That will wreak havok on the tires - it's better to have a set of rims and tires for the summer, and a set of rims and tires for the winter. My local Tires Plus store (where I bought the winter tires and rims) mounts them every spring and fall for free - they call it a "rotation" . It's a good deal.