An a-arm mounted with polyurethane bushings slides on the bushings. This
creates zero torque about the pivot point.
An a-arm mounted with rubber bushings flexes the rubber bushing to move,
because the rubber adheres to the a-arm and the frame mount. This creates
torque about the pivot point. The more the motion, the more the torque.
As such, a stock rubber bushing is more likely to bend an a-arm than a
polyurethane bushing is.
Now with suspension bind, things change a bit. Take a Spitfire with it's
swing axle rear and the radius rods. It's a bind design, and for that
suspension to move, the radius rod uses rubber bushings that allow for
stretch as the suspension moves up and down. If you replace the rubber
bushing with a solid bushing, the spring, body tub, and vertical upright has
to do the flexing instead, and cracking can result. Urethane is far from
solid though, so it still works, but more stresses are imparted onto the
metal bits and pieces..
----- Original Message -----
From: "Greg Perry" <rgperry@earthlink.net>
Subject: [TR] Use of Polyurethane Bushings
> Hello List,
>
> Has anybody considered the effect of using polyurethane bushings on the
> suspension (frame) mounts or suspension arms? Are there any occurrences
> of suspension failure due to using polyurethane bushings? I have read
> were modern cars have stamped control arms that may twist when using
> polyurethane bushings. I have polyurethane bushings on my TR6.
>
> Inquiring minds want to know! Any thoughts?
=== This list supported in part by The Vintage Triumph Register
=== http://www.vtr.org
|