..The spring hanger bushings on boat trailers are put together dry and I have not found anything that stops the annoying squeaks but taking the thru bolts out and bushings and coating them with a good lithium grease..Rollers too...I packed the rollers on one of my 1200 LB EZ Loaders and when I went to launch "Houdini" he pulled me into the lake..Some of the Calkins leafs were so cronic we would pull the springs and coat between each leaf with grease..Offshore made parts didn't help this problem....