I towed a trailer with a 480 lb. tongue weight and the Frontier settled 2.5 inches when hooked up. The leaf springs bottomed out against the frame/axle stop during our trip. It took me less than an hour to install the SSR-610-10 blue SumoSprings and with them added the truck sagged 1/2 inch with the same tongue load. I was able to use the same axle ubolts. I have not noticed a difference with ride quality and handling when unloaded. Thus far I am very pleased with this suspension enhancement.