A friend used them in a half leaf late model. Of course with a panhard bar, there's a lot of lateral movement. He felt it helped free some of the bind.
On a full leaf, because the spring is trying to twist, can change some of the effects. What works for one may be a curse for others.
When I raced leaf spring modifieds, I ran them when I ran composite leafs. They worked well in that application. I tried them with steel leafs but found rubber bushings to be much more consistent. Like 95Shaw said, it may work for one.
Bookmarks