this was a good explanation also:
The distribution bar sway controls need hitch weight to work - basically when the truck and trailer is in a straight ahead position the ends of the equalizing arms are centered in mating notches. As the trailer moves left or right the arms ride out of the center position and apply pressure to the slanted sides of the notch, pushing the trailer back to a center position.
This makes the hitch self-centering - the hitch is always pushing the trailer back to center. The only adjustment is the amount of tension you put on the equalizing arms, and it works equally well on dry or slick pavement.
A friction bar resists motion in both directions. If they're adjusted too tight they can actually lock the truck and trailer into a turning position if the rear axle of the truck loses traction. This is why their instructions say not to use them on gravel, dirt or in slippery conditions.
quote--Hitches like the Hensley and ProPride fight sway in a third manner - they move the effective hitch rotation to a point closer to the rear axle so the trailer tracks more like a 5th wheel. With the pivot closer to the rear axle, side forces on the hitch have less leverage to affect the direction of the tow vehicle. They do this by locking the trailer's A frame to the hitch head, so they both move as a unit. Levers inside the head act as a parallelogram, moving the hitch sideways as if the trailer was rotating around a pivot located further forward.
« Last Edit: August 26, 2012, 08:37:18 PM by Lou Schneider »-- end quote.
