Re: {Chrysler 300} 1960 Cross Ram power brake booster
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Re: {Chrysler 300} 1960 Cross Ram power brake booster



hi — your problem is magnified is if you fitted a larger bore disc master ( that what you meant?) you have thus  reduced line pressure ; this  is a hard trade , if you use original bore size you will get the lower pedal force / correct pressure in lines  as designed , on foot pedal—  but then it will travel maybe 20 % more to get the added cc  disc brakes need over drums . Long pedal travel makes driver uncomfortable . “ almost hits floor” That is because of the large piston in a disc vs drum needs more fluid . I assume you have 10 psi residual pressure valves on discs to keep them “ out” and balance valve on rears if drums ? 

 .This has been discussed quite a bit on here , — the “ problems” with the stock  drum are almost all due to “experts “ who have no idea how to do it right ; Done right they will stop  just as fast as any disc ,  they will lock wheels . The superiority of discs comes into play in the mountains , ( multiple hard stops down hill ) or more than two stops in a row from 100mph  or so . Or racing . Drums cannot store as much heat as large discs ,cool faster —  although the necessarily small discs to fit inside 14” wheels are like what is on a dodge dart , weighs thousands less than 300 — Right? may even be weaker storage than  drums . Weigh rotor weigh drum . 

I am not being a wise guy , i could not get the drums to work right either , when I started on 300 ‘s in 1970 or so , 3 attempts on  same car ( G) all new stuff, all poor results .  frustrated me and local brake guys too( who were not very good).  so so they said “ those brakes are a poor design” etc etc . And I bought that . Lived with it . Slowly got better . 

But then I found a young guy at a specialty brake place in Cambridge ma, ( Cambridge Brake) all they did was brakes. 
He says leave it , I did  , next day , Perfect . At first he would not tell me , later became a great friend . Precision fit of shoes to drum is key . Brand new parts do not meet the fit  requirement , do not touch fully , often for thousands of miles if fitted wrong . 
I knew brakes were terrific  new from mopar as my dad had new a 60 dodge no booster , same design , brakes  were fantastic . Best modulation or feel in industry and did fine in nascar right? arguments on this in 60’s with friends with GM power brakes confirmed this . A B comparisons. GM had “ all on , all off , feel” 

So knowing that I next built a 300 with no booster , like the dodge ( you have to change pedal ratio , relocate master on firewall , lot of work )  AND front  discs , . This was also no good , pedal way too hard and long travel . Discs take more PSI . And more volume.

 Then same , front disc with a booster = ok , travel a bit long , but for sure  not better than drums done right .But seemed not to have the “ whoa” power of stock drums  if you really stepped on it . ? Disc too small? 

  Despite everyone saying it’s better —( they just did it— has to be better! laugh ) it’s not better than drums working right . Which is frankly rare . And drum disc matchup has a history of problems of its own that balancing valves do not fix . They do not “ track” each other . 

Just sharing 50 years of this , =keep it stock

 READ EVERY WORD in chrysler service publication on these brakes ( circa 59 or 60) especially the part about matching shoe diameter to drum to the tolerance which is tight . But today no shoe grinding machines around , fear of asbestos dust etc . . Or if you have used ones with 1/2 the lining left don’t grind drums or put  in new linings . You will start the dance . You are not going 100k more  miles , old ones  are nicely matched . 

4 wheel big discs maybe , but that is 16” wheels , wrong  wheel covers non stock large or remote  booster etc etc 
Like J if you have rams 

Just where I am after all this time , admittedly opinion , but no rose colored glasses either about “ improvements “ . Been there. 

I noticed Big Red at Philly meet , the race 62 ram that set a lot of records was exactly like that 60 dodge — no booster , single master , pedal ratio / pedal from  a dodge or plymouth six , drums . 5 years in —— on exact same brakes —- the race  pros  came to same place as I did . No dependence on vacuum either . 
Hope this helps you ,
John 

Sent from my iPhone

On May 30, 2024, at 8:22 PM, RICK AND DEBBIE CLAPHAM <rixpac@xxxxxxx> wrote:


The booster is needed, it takes 30 percent more pedal pressure to stop the disc brake equipped.  I found this out in 1976 when I modified 73 d100 disc brakes on my 300G. The club members were not impressed. At that time. I didn't mention the A727 swap. That went unnoticed. 

Sent from my Verizon, Samsung Galaxy smartphone
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From: 'MILTON SIMON' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Sent: Thursday, May 30, 2024 4:59:27 PM
To: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} 1960 Cross Ram power brake booster
 
I’ve converted my Brakes to disc brakes with the dual circuit master cylinder. I’ve fitted that larger brake cylinder on my original vacuum booster. I’m not satisfied with the booster and power brakes.

I want to know your opinion as to whether the old power brake booster is necessary With disc brakes or in the alternative, what people are using with the long rams for a power brake booster other than the original unit?
Thank you, Milt Simon
Sent from my iPhone

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