IML: Rear Springs / Rear Steering

["Eric" <gearhead@xxxxxxxxxxx>]

I'm not sure which year started the practice, but by the 1965 model year, 
the rear leaf springs were not a simple, cost cutting, loss leader 
suspension setup, but an engineered system that incorporates an amount of 
rear steering and lateral stability as the 1965 Master Technician Service 
Conference booklet on Roadability and Handling illustrates.

As found on the incomparable Imperialclub.com website, a website who's value 
is nearly priceless and worthy of monetary donation (note to self: send in 
that check) this page in the technician's booklet describes the geometry 
with which the live rear axle operates: 
http://www.imperialclub.com/Repair/Lit/Master/214/Page05.htm

Of note to this thread, it specifically defines what happene when springs 
are installed that remain arched when the car body's weight is put on them. 
This effect takes away from the lateral stiffness that a flat leaf provides, 
allowing more sway. The original question of Steve B.'s was about going with 
HD springs or standard. When I had my '72 Newport Custom, it had the 
optional A32 Trailer Towing Pkg that had the HD suspension which merely 
incorporated an extra leaf. The assembly was pretty flat as intended.

I understand that a good result can be had by just renewing the one longest 
leaf in the existing leaf assembly. I haven't tried that but it might be 
worthy of investigation.

That technician's booklet section link is a really good read for those who 
may have thought leaf springing was in some way antiquated or of lesser 
quality to the competition's coil / track bar setup. It's so good, here's 
the link again... 
http://www.imperialclub.com/Repair/Lit/Master/214/Page05.htm

Happy understeering!

Eric
Lebanon, Oregon 


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