The four front rollers on my boat trailer (two on each side) do not
make flush contact with the hull so more weight presses on one side
of the roller than the other. As a result there are numerous cracks
in the rollers on the side that bears the weight. I intend to replace
the rollers and they appear to be held on to the W-shaped brackets by
metal caps that are simply hammered on.

Are there any tips or tricks involved in doing this? Should the
W-shaped brackets be fixed so that the rollers make flush contact
with the hull?

Thanks in advance.