If your SUV has leaf springs in the rear (don't know much about the Ex's) the front half of the leaf spring is attached to the frame with a solid mount. When you add the weight of the trailer on the SUV the truck squats down. The laws of physics states that when you have a reaction there is going to be an opposite reaction. The natural arch in the leaf spring is flattened out when the load is applied so the front of the leaf spring is naturally going to lift the front of the SUV. Now when you add air to the bags, the weight on the truck is not changing but you are relieving pressure from the leaf spring allowwing the spring to relax also allowing the weight the spring was taking off of the front axle to return to the front axle. Make sense?