Re: IML: Rear Springs / Rear Steering

[randalpark@xxxxxxx]

Well put Eric.

The design of the rear suspensions was as critical to the stability of 
the car as that of the front. The fact that it is simpler is by no 
means an indication of a lack of importance to the car as a whole, or 
the integrety of the original system.

The basic design for the rear began with the 1956 model when the split 
drive line was introduced, along with the hotchkiss drive incorporating 
the rear axle support struts. For 1957 the handling package was 
complete, and there hasn't been anything built since that has been 
comparable.

Driving a well mantained '57 through '66 Imperial at highway speed on 
good road is an experience that is as unique as it is satisfying. 
Owning one of these cars means that you should either be dealing with a 
VERY qualified suspension shop, or have the skill and tools to work on 
it yourself. Tire shops and other chain based "service centers" can't 
handle the job and may do damage to the automobile.

Paul W.


-----Original Message-----
From: Eric <gearhead@xxxxxxxxxxx>
To: mailing-list@xxxxxxxxxxxxxxxx
Sent: Fri, 3 Aug 2007 11:59 am
Subject: IML: Rear Springs / Rear Steering


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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