The official procedure in the Ford Service manual has you do it with the wheels on the ground. The manual says that when going up with the suspension, no settleing time is necessary. When going down, it recommend going down past where you need to be and then come back up to the proper height. It says that it can be done with the wheels off the ground, but it recommends taking the vehicle for a drive over varying terrain types to allow the suspension to settle. Then you have to take another measurement and make another adjustment if it isn't right. The last several times that I have adjusted mine, I have done it with the wheels on the ground using my 1/2" drive ratchet and 13mm socket. I have no problems turning the bolt and I am far for overly strong.