The 245-50s are about 8/10" wider and about 1/10" shorter OD than the stock Dunlop 18s. My thinking was the extra width and H rated sidewall would compensated for going with a lower profile. The high tech design and rubber compound of the MXM4 should also help reduce the impact wider tires have on MPG; more drag and friction.
After 50 miles a couple things come to mind when compared to the old Dunlops. The ride is more supple and impacts seem to be more cushioned. Road noise is more muffled. Steering feel is a touch slower than the V rated 225 Dunlop were when stretched across the 8" wide rims; a feeling/perception that will fade away after a couple 100 more miles. It is too soon to tell if there is any real improvement in handling but so far so good.
The MXM4 has put down some good numbers in the Tirerack tests. Living in the wetlands the wet track numbers were what won me over. The MXM4s can also be X rotated which is a feature I had wanted.
http://www.tirerack.com/tires/tests/tes ... p?ttid=138
