when I bought my compass in December it had a set of 230/50R18 snow tires on it, when I went to buy my summer tires, I bought the proper sized 215/55's. research tells me they are interchangeable with a 0.2" difference in height. The difference in driving though is unmistakable, I get 25% better gas mileage, 0 road noise, and almost double the acceleration, that can't be all drag from snow tires (other than the road noise). Maybe the bridgestone turanza el400 is just a really great tire, but I doubt it based on the fact that it was the cheapest I could find....