Fw: [Chrysler300] Center Plane Brakes

["George Riehl" <longrams@xxxxxxxxxxxxx>]

What a wealth of information a "little" brake squeal problem can bring to life!  This is what the list-server is all about! I am so glad to have some other very knowledgeable members contribute to history. Hopefully, all the "young" guys know what we are talking about. 
Having owned a '47 Ply, '48 Ply, '48 T & C Cvt., '51 Saratoga, '53 DeSoto cvt., '54 N.Yer. H.T. and a '55 Imp. sedan, hands-on work was performed by me. Both the Saratoga Club Coupe and New Yorker Special Delux 2 dr. H.T. (a Golden Falcon) was bought new by me. By the way, that N.Yer. cost $4,711.53 out the dealer's door. To buy the comparable car of today........$30K+?
Other than whatever had to be done by warranty, I did all the other work by myself and loved it.
(Now I am really telling you all just how old I am). 
  George 





----- Original Message ----- 
From: RWestra@xxxxxxx 
To: longrams@xxxxxxxxxxxxx 
Sent: Wednesday, April 08, 2009 12:30 PM
Subject: Re: [Chrysler300] Center Plane Brakes


I worked on the Center Plane brakes when they came out in the 50's and I recall problems with squealing and grabbing.  I also recall the service bulletin George Reihl referred to.  I tried the saw cut several times with mixed success.  I, like George, have no idea why it was successful when it was.  

We also experienced problems with grabbing, or pulling,  and had a great deal of difficulty correcting these problems.  I believe this was the result of manufacturing variances in the brake anchors and the variation of the profile of the heel on the shoe.  

The Center Plane brake was Chrysler's last attempt to avoid buying brakes from Bendix.  Chrysler had used a Lockheed design for many years and fought hard to give in to Bendix.  The Bendix brake was self energizing (it still is).  That is; the rotation of the drum against the shoe when the brake was applied forces the shoe harder into the drum.  Chrysler, with the Center Plane brake, accomplished this by the floating heel of the shoe being in contact with an anchor that was placed on an angle so the rotation of the drum against the shoe caused a wedging action that forced the shoe into the drum making it "self energizing".  This was an improvement over the fixed heel anchor of previous Chrysler brakes. The concept was fine except the variation in cam position and the profile of the heel of the shoe was very critical and resulted in the amount of self energizing to vary causing pulling or grabbing.  This also changed over the life of the brake.  

Chrysler used two forward shoes in each front wheel and one forward shoe in each rear brake.  This meant that six of the eight shoes were self energizing in the forward direction and actually self de-energizing when in reverse.  Only the rear two shoes in the rear brakes were self energizing in reverse.  This is why these cars are so hard to stop in reverse.  

I believe it was the introduction of the self adjuster by Bendix (and perhaps the problems with the Center Plane brake) that finally caused Chrysler to say uncle in the mid sixties.  

                                                                                            Rolland Westra.  


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