RE: [Chrysler300] Magnum Force disc brake conversion
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RE: [Chrysler300] Magnum Force disc brake conversion

No , Mike…it is not about expanding fluid…fluid expansion does not move the in board stop of the master piston …..the master (usually) stops against a mechanical ring , or end piece a part of master , pushed out by its inside spring, nothing adjusts. . When you step on the pedal in a ram 300, the first small movement opens a vacuum control at the top that starts the vacuum boost action (settable) which adds to that foot brake force. It has to move some before contacting the hydraulic or that co ordination may not happen as designed . Or happen intermittently ,even worse. 


By no means am I telling you what to do,!!!----  just important to understand is not like an in line , or manual system that will work ok if even .005 or .05 or .1  clear ; the clearance on manual brakes (and this too) is to be SURE the master seats itself, all the way out , with foot off pedal, plus some NEEDED safety tolerance, which allows fluid to come back in when foot is off pedal--- as rod is for sure  far away from piston, no matter what. Why pedal has its own return spring too.  (re your jag experience, locked the brakes—fluid could not come back in. ) Internally the back seated piston uncovers a port,  when full out within itself, to the back of car, against its mechanical stop, that lets the fluid come back. Important to understand that, ---and without a booster we are now done. Yes tightening that space raises pedal, but if too tight = risk of (due to bending , wear, whatever)  it not clearing free, =locked brakes. With an inline booster we are done, too , essentially same setup. ; 


BUT--- with the top trigger mechanism, that  has to start acting before hydraulic,  or with it, ; you could still have brakes but no boost ,----although I have never set this up personally . Or vacuum boost won’t release, locking brakes that way. Obviously many combinations can “work “ but be on the edge of a big problem. What bothered me was the comment about “expanding fluid” re: this gap,  shows some misunderstanding of what is going on..trying to help you.


With no boost these cars have a rock hard pedal, very hard to stop the car.


I think .050 at master is very good ---for manual brakes , but have no idea , not sure in the context of tripping this upper trigger device reliably …


All this, = More by way of understanding it ….than any number or recommendation . Most of these cars seem to not have a real high pedal, which is sort of disagreeable. I think most of that is in the wheels.


I think power ratio off pedal pivot is about 4.3 : 1,  fyi, so .050 is .23” it adds  –not much. , but other things add to lash. Not just that gap. Worry is not actuating boost if too tight here…or locking through locked booster. 


Someone like Booster Dewey might help you do this right, as yes there must be a setting , and “how to” -- for both gaps .Iterating it , however, might be dangerous??. 

Maybe someone else  knows a lot more about this? 

From: Michael Moore [mailto:mmoore8425@xxxxxxx] 
Sent: Monday, February 22, 2016 3:41 PM
To: John Grady
Cc: David Schwandt; dverity@xxxxxxxxxxx; Jean-Yves Chouinard; Chrysler300@xxxxxxxxxxxxxxx; Andy Mikonis
Subject: Re: [Chrysler300] Magnum Force disc brake conversion


Hi John, I understand and agree. 

The clearance  (I assume) is to accommodate thermal expansion of brake fluid . But one has to wonder  how valid a “factory adjustment”  is after half a dozen master cylinders and 3 or 4 boosters (both sides of the gap changed repeatedly ) over the 50 years and 300,000 miles I’ve had the car .

Chip Chapman once sent me a tool (gauge) many years ago to set the booster clearance, but it is now gone. I  would sure like to know what factory clearance setting was. I used .050 because that’s what my Jaguar is and it seemed like a good place to start.  When the S1 Jag E type was too tight, it locked up the wheels. Just that small amount makes a great difference in pedal height because of the ratio from the pedal pivot point to the pedal compared to the picot point to the MC plunger.

Mike Moore



On Feb 22, 2016, at 12:29 PM, John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:


May not trip the power booster correctly, the upper trigger, ..----you cannot go freely tightening that clearance one day no power brakes ---when you are happily expecting power, = you crash. Why they say not to mess with it. heads up. !!


From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Sent: Monday, February 22, 2016 10:15 AM
To: David Schwandt
Cc: John Grady; dverity@xxxxxxxxxxx; Jean-Yves Chouinard; Chrysler300@xxxxxxxxxxxxxxx; Andy Mikonis
Subject: Re: [Chrysler300] Magnum Force disc brake conversion


The greatest improvement to my 62 braking system was to set the clearance between the pushrod from the booster to the mc to around .050. I was never able to find the correct number, but it sure raised the pedal substantially.

Mike Moore


On Feb 22, 2016, at 6:59 AM, 'David Schwandt' finsruskw@xxxxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:



Brake system doom and gloom is all I hear on the Forward look site as well,
how bad they are and should be pitched and replaced

Same story w/the ball and trunnion U-joints that were used for how many
years on MoPars?

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of 'John Grady' jkg@xxxxxxxxxxxxxxxxx [Chrysler300]
Sent: Monday, February 22, 2016 8:57 AM
To: dverity@xxxxxxxxxxx; 'Jean-Yves Chouinard'; Chrysler300@xxxxxxxxxxxxxxx;
'Andy Mikonis'
Subject: RE: [Chrysler300] Magnum Force disc brake conversion

With you 100% Don..

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of dverity@xxxxxxxxxxx [Chrysler300]
Sent: Thursday, February 18, 2016 7:38 PM
To: Jean-Yves Chouinard; Chrysler300@xxxxxxxxxxxxxxx; Andy Mikonis
Subject: Re: [Chrysler300] Magnum Force disc brake conversion

I think the 12 inch brakes were a heavy duty option on the Dodge and

I have never had issues with the original drum brakes that I haven't been
able to fix. Linings separating from the shoes, and stretched springs come
to mind. I always do new master and wheel cylinders, and don't turn the
drums unless they need it. If there are hard spots on the drums, you can't
remove them with a regular brake lathe. An old time shop that used to be in
this area had a grinder attachment that could be used on their lathe to take
care of hard spots. They also arc grinded shoes for many of my cars. I have
my own arc grinding machine now thanks to the late great John H.

I have had issues with disc brake conversions, and dual masters though. The
pedal ends up being way to low for comfort, and the stopping power is not
that much better. The plumbing is a pain too. Chrysler designed them well in
the first place. 


From: mailto:Chrysler300-noreply@xxxxxxxxxxxxxxx 

Sent: Thursday, February 18, 2016 6:36 PM

To: Chrysler300@xxxxxxxxxxxxxxx ; Andy Mikonis <mailto:r41hp@xxxxxxxxx> 

Subject: Re: [Chrysler300] Magnum Force disc brake conversion

Very interesting info Andy, thank you for sharing.

Surprising that a 2100 pound Daimler with disc brakes took 33 feet more to
stop!! Chrysler brakes were not that bad!! Dart a few hundred pounds less
than the G, explains the 125 feet for the Dart, which probably was equipped
with 11 inch brakes ...vs 12 inch for G.



From: Chrysler300@xxxxxxxxxxxxxxx <Chrysler300@xxxxxxxxxxxxxxx> on behalf of
Andy Mikonis r41hp@xxxxxxxxx [Chrysler300]
Sent: February 18, 2016 5:11 PM
To: chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] Magnum Force disc brake conversion 

Yes, John, I agree. One of my mechanic mentors who opened a service station
in 1957 always told me the problem with these brakes was with the mechanics
and not the engineers.

He always arc ground. (In fact, I have his arc grinder now.) The linings he
ground for me in 1990 are still on my G after 100K+ miles.

Other things I have published in the club newsletter the newbies wouldn't
have seen:

Paul Mallwitz, a Chrysler engineer who spoke at a club meet in 1982 was
asked: "How did you get the brakes to work on these cars?"

Reply: "With great difficulty. Those Center Plane brakes had to be put
together like a watch in order to make them work properly."

Next, in the April 1961 issue Motor Life magazine tested a 300-G and
recorded a 60 to 0 of 131 feet. That's average for today's cars. Mistake?
Don't think so. Dart D-500 in the same issue: 125 feet!

Other cars in the same issue:

Olds Super 88: 159 ft.

Olds F-85: 171 ft.

Daimler SP-250: 194 ft. (2090 lbs. with disc brakes)


300 editor

In a swiftly warming Chicago

On Feb 17, 2016, at 1:18 PM, 'John Grady' jkg@xxxxxxxxxxxxxxxxx
[Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Just a FYI< 

A lot of the fitment differences for a total upgrade are because they
changed at various times the lower (at least) ball joint OD , how it fits,
(press or screw in to lower arm) and the size of that ball joint taper that
goes into the steering knuckle. I know it was long ago, details not 100%
clear tonight , , but I put 67-68 Dodge police car package steering
knuckles, discs and ball joints into 57 Dodge control arm by reinforcing
the end of lower control arm with added ring of 1/4" steel and then boring
that out for what I think was the larger (than 57) 67-68 lower ball joint. I
think top 57 one fit the knuckle or spindle ok, or found one that fit. .
That let us put on stock 67 or 68 police car disc brakes, the "big discs"--
hot set up long ago --before disc kits--- on 57 Mopar. 

Now they have kits that fit the old knuckle.and leave the small ball joints.
Two kinds of kits?? ..special adapter knuckle-- or not . By way of
awareness, not comparing. But insight into why some years and not others.

This change to discs on my 57 was made , really, because I had frankly
screwed up more than one total contact brake setup, through not knowing
what I was doing, after buying all new parts, , and was fed up with "all
the problems". They are real problems. But is it the brakes? 

I had a brand new 60 dodge , in 60, manual brakes , bought then because I
liked two leading shoes on the manual, had heard and seen many horror
stories about power brakes in general 55-60, --60 Dart was a great set up! I
beat it unmercifully. It was perfect in every way , brake wise; used to
laugh at best friend's GM 57 Pontiac power brakes with on-off feel. Beating
unmercifully, was street drag racing several nights a week to 100 mph + ,=
going was the problem, not stopping. No pulling no grabbing..

The basic torsion bar suspension design is about the same across these
years ; all this by way of info, not advocating doing it, but good to think
or know about. . 

Do you need discs?? Sort of falls out of it? Idiot proof as far as
assembling the pads..

I am in the middle of doing some discs, but still ambivalent. Not if drums
are working right, is one answer. They worked right at the beginning. 

Also looking back, many of the problems with total contact , or other
Chrysler brakes are errors caused by experts (who are not) in putting them
together right, especially arcing the new shoes to a turned drum. If you do
not, with all new parts, the brakes do not work. Discs get into front/rear
balance, another possible can of worms, despite that balance "valve" . They
have inherently different actions..

They won all those NASCAR races with them, stories about "fade" on the
street leave me cold. Worse than fade--- -------if the shoes are not
touching the drum , most of the way around! 

Sure , not as good as modern discs, but awfully good brakes. 

Did you know GM put MOPAR total contact brakes on the racing Corvettes with
Buick drums about 1960?? they watched the 300B race, brakes and all, and
win . . So would I. On a light corvette? Bulletproof . And the "fading after
3 panic stops from 120+ mph" in contemporary 300 tests is not exactly how
we use our cars today. What reminded me of all that , was seeing that 300B
race clip a few weeks back , on this site . No disc conversions , yet racing
competitively for real, in 2015? Braking hard on corners over and over...
(he did have Buick drums too..which have aluminum fins on them. 60 to maybe
62. That forces a wheel change too ). Before discs, that was the hot setup.
Rods, Bonneville etc . The brakes we take off. 

My problems with these brakes on 300F over the years was not fade..they were
pulling, grabbing, low pedal , poor stopping rate, squealing etc etc . 300
B or 60 Dart was not like that .. Why?

Just sayin..there is a disconnect here somewhere. Others see it? 


From: <mailto:Chrysler300@xxxxxxxxxxxxxxx> Chrysler300@xxxxxxxxxxxxxxx [
<mailto:Chrysler300@xxxxxxxxxxxxxxx> mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of 'Bob Jasinski' <mailto:rpjasin@xxxxxxxxxxx> rpjasin@xxxxxxxxxxx
Sent: Wednesday, February 17, 2016 4:46 PM
To: 'John Nowosacki'
Cc: 'Chrysler 300 List'
Subject: RE: [Chrysler300] Magnum Force disc brake conversion

I sent them an email. I'll report back with what they send me.

Bob J

From: John Nowosacki [ <mailto:jsnowosacki@xxxxxxxxx>
Sent: Wednesday, February 17, 2016 1:22 PM
To: Bob Jasinski
Cc: Chrysler 300 List
Subject: Re: [Chrysler300] Magnum Force disc brake conversion

pictures say 57 to 61, but when I click on the link for picture or part
number, it says 65 to 72?

On Wed, Feb 17, 2016 at 3:42 PM, 'Bob Jasinski'
<mailto:rpjasin@xxxxxxxxxxx> rpjasin@xxxxxxxxxxx [Chrysler300] <
Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Has anyone looked into or installed the disc brake conversion kit offered
by Magnum Force?


They offer several kits and appear to be fairly new offerings. 

Bob J

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



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

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

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