In my experience, they were turning while I was driving - not affected by loading. They were level after loading the kayaks and before leaving home or the takeout. When I arrived at the put-in or back home they had rotated to the rear. The bars were held to the towers on one side of the vehicle by drilling through the tower and bar and fastening with a screw, so I know the bars were not rotating. The rollers and saddles were fastened to the bars with carriage bolts and nylon locknuts, not the wingnuts Yakima supplied. The nuts were cranked pretty tightly. Nothing I tried eliminated the rotation. And I did use both straps and bow & stern lines.