FX35 Buckboard

Eagle 1

New member
My wife saw this Infinity FX35 and had to have it, it is beautiful, and runs like a demon, but rides like a buckboard. I took a 2008 Murano out for a drive and it rode excellent, I couldn't believe they are essentially the same vehicle. The only visual difference I could find is the Murano has 235/65r18 tires and the Infinity has 265/65r18 (around 1.25" wider), could this be the difference in ride and if so what would be the problem in changing the Infinity to the 235's?