According to
http://www.rimsntires.com/specs.jsp a 245/35/19 on an 8.5" wheel in the front paired with a 285/30/19 on a 10" wheel on the back matches up perfectly. A 255/35/19 and a 295/30/19 also pair perfectly but I don't need new front tires and I'm worried about the 295 rubbing.