The bar is not resting flat on the support bracket. That is, it's tilted inward just a bit, so that all the load is on the inside edge, and not on the entire lower surface. As you make a turn, the bars move side to side, and the increased pressure due to the smaller surface area of that edge, means the bar's edge is gouging into the support bracket(s).
The good news is that as things wear in, you will see that wear pattern get wider. This groove will soon be on the same small angle as the bar, meaning the surface area is increasing as it wears in. If fact, I think I see it starting to touch out at those pins. As surface are increases, pressure decreases, and the wear should slow down.
I would let it wear in, but watch for corrosion issues. After things are settled in, perhaps you could have those brackets re-coated.
If I were the design engineer, I would enlarge the holes used to pin the bars at the front sockets. This would allow the bars to lay flat on the brackets in the new condition.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
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