RE: [Chrysler300] 300G Rear Brake Backing Plates; ----Brakes in general
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RE: [Chrysler300] 300G Rear Brake Backing Plates; ----Brakes in general

Hi Ron,


It is thicker mid 58 up ; thin adjusting plates  are 57 to mid 58, possibly the 300 only (?) had a change mid 58.Wheel cylinders too. (they  have to change cylinder mount foot with plate mount thickness, only difference is the mount thickness, as far as I know  ) Control arm bushing size changed too, so control arms changed/beefed up , not sure if frame mounts changed too.  . 300 mid 58; I think they changed the others / the rest of the car line ( Desoto, etc ) in 59, but do not know this timing for sure. .You have to look at individual cars. Part numbers not always helpful, they are often screwed up in 58 for sure. (found out , after a go around with wrong MOOG parts listed in MOOG catalog for 58 ,  both sizes were used in 58, possibly 300D late only---- they had some D with upgraded parts–they knew a problem ---upgraded 300 first, pre 59?) . Some parts , which are the same thing,  have different part numbers too. 


I know this because we , J-Y and I, put 59 Desoto LWB 12” complete assembly,  thick  newer style EFG  (H?) adjusters on 58 Chrysler 300D  w 60 wheel cylinders, that D formerly had thin 57-58 300C ones stock, 59 Desoto 12” LWB dual exhaust V8 is the same 12” as 300F,G , E and I think H ; once upgraded late 58, 59 they did not change again, to my knowledge, on up to 62 .Other stuff around trans obviously changed in 62. I have never worked on a 62. So hot setup is 59-61, possibly 62 12” setup with matching control arms? Not sure if new control arms fit stock C control arm mounts , as we changed frame too on 300D to the rust free 59 Desoto (terminal rust on D) . Control arm mounts might be different.


While on that, LWB 4 dr sedan frame is the same as 300 , except X (convert) and welded on bumper mounts which we moved from the old 300D frame . That surprised me. Good to know basic frames are all the same , for a wheel base ; while looking at 57-59 300’s, the frames dissolve at kickup curve just in front of rear axle. 


This from real cars ---not parts books ; we had a pile of F stuff listed as also used on D, but did not fit. After some investigation the info here approximates what we found out .We put F or Desoto upper control arms on D , but with Desoto frame Possible upgrade for 300C too, to F/G brakes, possibly to better control arms too..check control arm mount tabs  . Maybe someone who knows about 55 /56 can chime in here too. 55/56 Might be the same brakes as 57? What were Kiekhoffer  (sp?) brakes? Vaguely remember “Imperial brakes” ; they (55 and 56) were two leading shoes too, right? 12”?? Same as race car? Or Imperial brakes  upgraded that?


300C stock control arm bushings now look like toy Studebaker parts to me. 


*******Related, critical, and mentioned before, it is possible to assemble spring retainer (the long flat wire looking thing brake spring hooks into  ) absolutely wrong…and no real pictures are in service literature clearly showing how it goes ; loop sort of hooks around the stud/rivet near the far wheel cylinder  when right. The other flat end then goes inside the cam toward spindle, so cam is  acting between brake shoe and flat spring  retainer ; spring is squeezing them both together onto opposite sides of cam.  ..they move together, as you adjust, keeping spring stretched the same !  I have encountered several of these spring retainers assembled all wrong, ---two ways can be wrong…. The loop not hooked over the rivet , and can be put on wrong side of cam, if enough ingenuity, to get the shoe on top of it(!) . . . Which leads to long painful stories, as brakes can never work right.. 


Some critical numbers, shoes must be about .005 ideally and stay the same along the arc in the drum; it should take 45-55 lbs assembled to start the shoe away from wheel cylinder . Because they self energize so aggressively, as they should, if out of spec on fit to drum they will lock and grab unevenly ---this happens I think if only touching in a narrow spot of shoe, or half of shoe , because arc of shoe is wrong. I think this takes 4-5 k  miles, many adjustments of cams ,  to straighten out. Long and painful. Poor stopping power. 15% of shoe face working ! Frustrating , as all is new!!!  . Any rust from storage(normal) will make them grab due to immediate self energizing even if otherwise correct, so apply gently first day to wear off rust .If only touching part of shoe, due to arc problem it will wear rapidly causing pedal to fall as 2 wheel cylinders will soon come out a whole lot more to make the shoe touch, pedal moves down an inch or more in 1000 miles, with “new brakes” . . Cams did not move! But often blamed! The only force trying to move cams in the first place seems to be when shoe is out during stopping, spring retainer is trying to move the cam then, but only with spring force (?60 lbs?) ; remember shoes only move .005+  if all this is right, spring hardly changes.  ; however if cam does move , that seems to be  moving in the direction that tightens brakes not loosens them, as shoe will not go back to rest as far as it did before,  if retainer flat thing pulls the cam forward acting from the  inner place that it touches(back of cam) . . ( same as if you reduced clearance, moved cam, pedal comes up) ) There is no net  force I can see trying to make it (cam)  loosen!! .. But be sure cam is turned correct direction when setting, or all bets are off, possibly opposite can happen. .  So sitting and thinking , looking at how it works, might be more important than pulling the wheels .I am not turning drums anymore, because “experts” in past told me to . Unless out of round leave them alone. Internal scratches do not matter. Same with old half worn shoes. They will fit drum you have perfectly ; new shoes might get you into the “Total Contact Dance “ for a year or two. . Historically those who tell you must turn drum happen to sell drum turning services…and new shoes that will not fit correctly into them, without arc grinding..  Which they cannot do anymore. 


I had a brand new 60 Dodge , Pioneer 230 HP 318 stick coupe, manual brakes in 1960. Brakes were REALLY great ---zero problems for 40k miles. I used to argue a lot with a best friend with hot 270 HP 57 Pontiac with power brakes , how touchy the Pontiac brakes  were. Pedal effort on manual 60 was to me just right, excellent control of stopping power –with no booster. I noted Big Red has manual brakes…..and J-Y has a loaded ram 60 Polara ( same under the skin as 300F) with factory manual brakes(!!!) .  Word on the street in 60 was ‘big hassle” from power brakes from the 57-59 period—why Dart was ordered without them.. ; brake problems in the 1960 Dodge began with leaking rear wheel seal. Greases, oil,  even a tiny amount, fingerprints,  makes them lock up. Note that failed or no boost 300 power brakes does not result in factory Mopar manual brakes…ratio of manual pedal is totally different. Power brakes with failed power boost takes three people on the pedal. Firewall mount location of master cylinder also different vertically on manual compared to pivot at top of pedal. Mechanical advantage maybe 2- 3x better. Do not judge manual by failed power!


I could never understand why 300’s we see, are often totally the other way, very aggravating brakes. I grew to hate my 300F brakes back in 70’s , even after a lot of “work on them”  . NOW, I think the problem resides between the ears, lack of understanding, not on the car..but I am older now. Finding out more on all this is project 2016. I think they are about the best drum brakes ever, except the Buick finned aluminum ones, but those had only one leading shoe  ; GM agreed, even used 300 total contact brakes  on their race corvettes , with big Buick aluminum finned drums! ( they must have noticed huge heavy 300B did all right on its brakes,  (!!) in the 56 races…..with total contact brakes).


All this is why cams are stripped….smile.


Did not say discs till now!! TBD if as good , as balanced as working correctly Total Contact  12” brakes. Discs are essentially foolproof however. Except the front/rear action balance…..


From: Ron Waters [mailto:ronbo97@xxxxxxxxxxx] 
Sent: Wednesday, February 10, 2016 10:24 AM
To: John Grady
Subject: Re: [Chrysler300] 300G Rear Brake Backing Plates


John -


I believe the area where the wheel cylinder mounts to the support plate is somewhat thinner. Not sure though. 


Not sure if '62 is the same. You'd have to go to the parts book and verify the numbers.


Dodge usually had 11" brakes. So different parts. Wheel cyls likely the same.



----- Original Message ----- 

From: John Grady <mailto:jkg@xxxxxxxxxxxxxxxxx>  

To: Ron Waters <mailto:ronbo97@xxxxxxxxxxx>  

Sent: Wednesday, February 10, 2016 9:09 AM

Subject: Re: [Chrysler300] 300G Rear Brake Backing Plates


Late 58 ? 62 ? Why 58 wheel cylinders change mid year on300; thought 62 same but have no personal experience on 62 . Note m moore is working  on a 62 with studs . Watch out for 11 " dodge parts . Sold to you as samevthey are not obviously . Have those ! 

Sent from my iPhone

On Feb 10, 2016, at 8:35 AM, 'Ron Waters' ronbo97@xxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:


Just FYI...Late '59 thru '61 are all the same 3-platform brakes. 



----- Original Message ----- 

From: John Nowosacki jsnowosacki@xxxxxxxxx [Chrysler300] <mailto:jsnowosacki@xxxxxxxxx%20[Chrysler300]>  

To: Charlie V <mailto:cv300g@xxxxxxxxx>  

Cc: list server <mailto:Chrysler300@xxxxxxxxxxxxxxx>  

Sent: Wednesday, February 10, 2016 7:50 AM

Subject: Re: [Chrysler300] 300G Rear Brake Backing Plates


Those adjusters do have a tendency to freeze up over time if not adjusted periodically.  One fix I've seen in the past is to take a nut (like a 3/4" size) and weld it to the rounded off adjuster stud.  Now you have a 3/4" adjuster instead of the rounded off 7/16" that was originally there.  (Don't force it, get a bigger hammer!)


On Wed, Feb 10, 2016 at 5:32 AM, cv300g@xxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:


Does anyone have a SET of Rear Backing Plates that they are willing to part with.

I also need the Supports .

The Supports are the double plated device that the Brake Springs attach to and they also have the adjusters that go thru the backing plate to adjust the brakes. The adjusters on mine are rounded as if someone in the past used vice grips on them to adjust the brakes.


Lion Charlie Valentine

300G, 1962 300 Sport Convertible, 1965 Plymouth Barracuda


[Non-text portions of this message have been removed]

Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx>

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