Eslagel

I run 26.9" diameter tires on my 2010 MKZ, clearance is closest at the bulge in the rear side of the fender inner liner Towards the bottom when turning. About 3/16". If your 07 has the same suspension you should be able to run a 20" wheel just do not exceed 26.9" diameter tire. You need to watch the width of the tire that you choose and the back spacing on the wheel.