There are several opinions conserning this subject. I will give you mine. Tighten axle nut snug, just till it sees some resistance, then back it off to align the cotter key. Spin the wheel, it should run free, no hard spots, just spin freely. With proper bearing lube, you're good to go. After 25 to 50 miles, pull off and walk around the trailer placing you hand on the wheels near the bearing. A little warm is OK, but hot is not. Remember to give the bearings a pump or 2 after leaving the water. Watch the inside of the wheel for signs of seal failure,(grease), and plan on seasonal maintainance each year...MP