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Suspension Bushings

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  • Robert Kirk
        A question recently arose over the early and unsuspected failure of leaf spring rubber bushings in Crosleys.  I have only this year been able to source
    Message 1 of 1 , Sep 6, 2008

      A question recently arose over the early and unsuspected failure of leaf spring rubber bushings in Crosleys.  I have only this year been able to source a quality replacement polyurethane bushing for our cars and submitted this to a group of Crosley owners.  I thought this group might benefit as well. It was cyber penned when one owner voiced concern that poly imparts a "stiffer" ride.   
      A Hemmings Motor News editor read it and wishes to post it on their site.  I include his letter to me.

      A vehicle’s suspension has to do with sprung and unsprung weight. Spring steel, by its very nature and in order to be "springy" is NOT the best steel in the world but certainly does its job. The purpose of shock absorbers is to dampen the effect of the springs and "level" out the reaction of the springs. Both springs and hydraulic shocks have a "life span" especially spring steel.
      Further, the fact that VC and CD shock absorbers are no longer available in pure oil only dampening and instead now have high-pressure gas and oil, would be far more suspect to me why "harder" rides may prevail. It’s also worth mentioning that springs are at work even when the vehicle is sitting still. They not only "de-arc" over time they actually suffer metal fatigue and should be replaced. Now I know that likely flies in the face of a very few Crosley owners I have met who are most conservative in what they are willing to invest in their 60 year old vehicles which have never had anything done to the springs except, maybe, some new end bushes.
      In most US vehicles the anchor point of a semi elliptical spring actually has rubber encased in two steel tubes…inside and outside that would be steel to steel contact both inside the spring eye and fastener with only a small amount of rubber in the "sandwich". The work is being done on the shackle point, which rotates to accommodate the spring action. On a Crosley rear suspension with only a quarter elliptical ALL the work is done at the rear most shackle. The front, where the weight is, has full rotation on the shackle and smaller rotation ability on the "eye". Bushings are there to allow rotation NOT to impart ride quality, which is the job of the springs and the shock absorbers. IF one notices a harsher ride with polyurethane, I suggest the reason has a lot more to do with the quality of the springs and or shocks NOT the bushings which only serve to prevent metal to metal rotational action…much like cartilage in your shoulder, elbow, hip and knee
      Polyurethane is formulated to a durometer of hardness to nearly like steel to as soft as rubber bands. My formulation is slightly higher than what a "good rubber" formulation should be. What my customers and I are seeing in the past 25 years is a slow degeneration of rubber from US, UK and virtually any other source. It came to my attention when motor mounts for my British Car customers were delaminating and cracking before ever be physically put to their purpose.  Its also worth mentioning that rubber even synthetic degrade with time, UV rays, and ozone.  Polyurethane is affected by none of these with the possible exception of time...MUCH longer time.
      Bushings don’t make the ride one way or another. Their job is to allow rotation. Silicon brake grease is what I suggest for polyurethane. It is probably also applicable to rubber. Any petroleum based lubricant will likely hasten the death of anything rubber. Ironically they are NOT compatible. Thus the reason I also offer tie rod end boots in polyurethane for Crosley vehicles.
      Would you mind if I copied the following to the Hemmings Blog
      (http://blog.hemmings.com)? It sounds like you've done your research,
      and some of this information should apply to the collector car community
      as a whole, not just to Crosleys. We would, of course, provide a link to
      your website from the post.

      And if it's okay, do you have any photos we could run with it to
      illustrate the post?

      Daniel Strohl
      Associate Editor
      Hemmings Motor News

      Robert Kirk

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