It looks to me that it is caused by having a load (kayaks) at the end of a lever (the uprights) putting sideways pressure on the J bolt/s.
As the kayaks on the top move from center to left and right on the top (looking at the road from driver's seat), they exert load on the j bolts through the up rights. Which are now a lever. One end the j bolts, the other the kayaks.
I think the only thing to do since the level distance cannot be changed; is either to lighten the load, use a thicker diameter j bolts, or jay bolts made from a stronger material.
Some modification may have to be done to accommodate the thicker diameter j bolts.
Good luck.
Last edited by Mahigeer; 10-10-2015 at 06:38 AM.
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