I'm picking up a set of 18 inch Ronjon Inspyre wheels this weekend, and have been looking into what tires to put on them. These SPT's seem like a good tire, but even aside from that, would a 245/40/18 be a good size as far as keeping overall diameter similar to the stock 235/45/17 that comes on the car? I don't want to change the gauge readings much, but would like a wider tire.