I run Nitto Dura Grappler 305/75R18; 35.25" dia; in the summer time. As I have a 750 lb atv in the back for work, it sagged the rear 4". I had to build a new, extended tailgate therefore a lot of weight is behind the rear axle. Deaver built me a set of +3 that are made for 650 lb of weight. I put a pair of PRG 1.5" collars on the front. After taking out the factory 2" block the truck sits 1.5" higher than stock and squats 2" with the atv in the back. Truck rides great empty and perfect when loaded. The stiffer Deavers got rid of that "floaty" mushy feel I had before. It was really unstable at 100 mph. Have run Deavers on my last 4 trucks. Great product.