Poly bushings failing?

[russgt]

What causes poly bushings to fail? Heat? Age? Miles? I have been tracking down a wandering issue on my 89 Jimmy and swapped out the front spring bushings and all the sway bar bushings. They were all blown out like this.

[bdiamond]

Poly is really too stiff for a leaf spring bushing. The springs need to twist more than polys like. They are perfect for rotating in a single plane, but any more than that and they bind things up.

[Snailed]

Yeah, despite the advertising hype poly is not a good material for all bushings. I used to go through two sets of lower control arm bushings a summer on an old turbo car I had until I build arms with spherical ends. Poly needs to fit perfectly and only move in one plane as diamond mentioned. There is a reason many companies stopped using it for shock/air ride bushing too. It just doesn't hold up. Ridetech won't even sell you replacement bushings for the old shockwaves now and recomend changing to sphericals.

[Hart_Rod]

How old are they?