Re: {Chrysler 300} 300C brake drums

i have done that too , the smaller AAJ disc that fits in 14” wheels is good, but theoretically and practically about the same or even less brake stop torque = even less whoa power , — to me anyway — than stock (?stock working right) due to small active diameter or moment arm of the clamp force compared to a 12” drum . Physics , — unless way high psi boost . Which then locks rear . And for us , there is a lack of psi in 1960 , not needed . compared to a GM disc car . Let’s call it 67 dart level disc brakes on a much larger car . But yes idiot proof to get to work right .

The real Problems with brake fade with our drums has to be purposely induced — by 2-3 stops from 100 mph , or mountain driving — that issue is true — and is due to the energy you have to dissipate when stopping a heavy car.

the same total heat goes into a disc or drum , the ability to soak that up depends only on the weight or mass of rotating part but a disc cools way faster . Can do it again sooner . Does it really matter in a 300 ? Maybe in mountains ..

Huge 60 Buick aluminum over steel 3x 12” drums with aluminum fins are the best answer , as that race 300 B ( or a stock 60 Buick) shows . . Hot rod guys used those 30 years ago still do Look way cool too . Note that cooling has nothing to do with initial stopping fast , the first few times , - with systems cold . Only shoe area and diameter . gotta love the 3” wide . ours are 2.5

I also like the feel of total contact drum progressive action , discs are totally different , you really have to stomp very hard to get a lot of whoa on conversions . Disc power systems usually have higher boost pressures by design, will cover that issue up in stock use .

And that brings on the front / rear balance issue , cannot balance the over all pressures on a mixed system vs whoa. Inherently different due to drum self energizing

I got into “ proportional valves “ over that , as from an engineering perspective you cannot reduce pressure “proportionally “ without say stepped hydraulic cylinders etc . The little valve is too small and cheap a thing to have that . real race cars have two masters and a balancing beam between them to adjust or accomplish that , Yes to that, and someone once made a stepped bore master …

So what is in proportioning valve ? Questions to guys selling them show completely zero understanding , beyond “ you need it, and ours has a chrome knob” and “famous brand in brakes “ ( but their famous fixed calipers suffer from knock back of pucks in corners , you may crash , pedal travel changes erratically due to puck knock back between uses = wrong design , ( Can’t say that to the experts though ) GM caliper is correct , centers itself

So I took a proportional valve apart . What was in it was a needle valve .

Now , that slows flow , but end point pressure, and so stop power after a ? short delay has to be identical . So what it is doing is ? delaying back brakes , so fronts do a lot more work — for ? fractional seconds? this is BS to me . And more applicable to front disc rear drum to stop a rear drum self energizing quickly lock up on a sudden hard stop .

Nothing “proportional“ about that . If it said “ brake delay valve” might sell a few less .. laugh . But for average driver it is functional , sort of .

The last F I did i put the AAJ large disc , to try to improve on all this on a manual

master , needs 15” wheels , I used 17 to get good Michelin tires . There are no really good 14” tires , — way more limiting thing than the brakes too

And , my dad had a 60 dodge V8 brand new , no power brakes , — but had our same total contact leading shoe setup . Fantastic brake feel , without power —- and the two leading shoes you could readily lock brakes , no power —- but well before that , a beautiful controllable feel .I want that again Perfect front / back balance too , no vacuum bs either .

Mopar always changed the pedal ratio and master bore on manual . They knew their brake stuff cold, it was designed as a system by smart guys . Conceptually two leading shoes is the very best , but tricky to work on. Like a hemi .. or dual

points ..

Except for all the machining to do it , and 5” bolt pattern , Buick drums on mopar 12” total contact backing plates , no boost should be , probably are, the best brakes you could do on a road car , like that current road race B has — and probably all the B nascar winners were manual , ? big imperial drums ( were they power brakes? I bet not ) .

Buick did not have two leading shoes, I dont think any GM or Ford ever did. Even mopar gave up in 63 , — only due to service difficulties .

A runner up to Buick on our cars is a disc , with rear discs to avoid balance issue. I did that too on an F , custom made Cad rear discs to get good disc e brakes onto a dana 60 , but still the AAJ small fronts . Imperial had that on 60 in 74 era , but an unreliable design of small drum brake inside disc ,

You really need a power booster on “all discs“ , especially small discs to get enough stop , found that out the hard way

So the evolution , = now the big AAJ disc front brakes , a Dana with 12” Ford drums ,( to get a reasonable E brake setup ) “proportioning “ to rear ( can just leave it open, TBD) manual Corvette master( many bore sizes available ) large reservoirs ( discs take more CC to move it)! - our stock pedals thus move down too much-with didc conversion / especially small bore / or no boost —or stock drum boosted master — all subjectively )

The hood is increased whoa of big discs with small bore big reservoir master removes need for boost . tbd

Corvette needs are like mine ! It works there , although corvette disc calipers are a horror show .

Maybe one day do the Buick thing , no boost,

just like a stock F has but no boost , better drums in front .( called going full circle?) runner up is 100 % stock F with manual pedal parts like Dodge . I think the “Big Red 62 “ competition car we saw in Pa . was like that

We know Buick swap works, that big heavy race B is right there on road races with all the Euro hot shot 4wd discs , and is driven today ,Great “you tube “ of that car somewhere , gets into brakes

Of course today’s huge discs and computer controls , elaborate boost , traction control set up , fix all that . I don’t want that stuff .

To get that all you need is a down payment ,

can even buy a nice leather bra for the front , and service contract for 3500 .

Or get a silver camry . laugh

jkg

Sent from my iPhone

On Aug 24, 2023, at 9:24 AM, John Nowosacki <jsnowosacki@xxxxxxxxx> wrote:

There used to be a great place in Wakefield, MA called Stopping Products aka Wakefield brake. I would take drums and shoes to them for relining, contouring, etc. It was inexpensive and quick turn around. To no one's surprise with 20/20 hindsight, the shopped closed long ago when the owner/operator passed from lung cancer after a career breathing in asbestos dust. Just down the street was a great radiator and a/c place called Associated Radiator. Great guys who did great work, and that shop also closed due to cancer death of the owner/operator.
As hobbyists, hopefully we are not faced with the same level of exposure as these early career mechanics were, but using proper protective gear while working on your car is a very good idea.
Best thing I ever did for my 57 and 61 cars was an AAJ disc brake conversion on the front wheels. I can honestly say the improvement in stopping power is no more than 10 or 15 percent over properly adjusted original brakes, but there is no more even thinking about them since. No adjusting, no worrying about leaking cylinders, or anything else. A loaded Monte Carlo caliper/pad assembly costs a little less than one of the 4 wheel cylinders on a stock setup last time I checked. The only drawback on the G was that I had to change pads to ones that created less dust, as the vented wheel covers let the brake dust go down the sides of the white car, plus I had to buy 5 extra RH lug nuts for the later model Chrysler Cordoba rotors that replaced the drums on the driver's side.

On Thu, Aug 24, 2023 at 7:41 AM John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:
be careful ; if you have well worn in shoes etc with more than 30% or so left, leave it alone . scratches and lines are normal and your newly turned shiny smooth drums will look just like that in a few thousand miles anyway .

After fighting with getting total contact brakes to work right ( they are great when calmed down / worn in ) it took a lot of pain and lesson learned the hard way stuff to figure out how critical the match of drum ID to shoe OD is .

See that chrysler factory service publication on these brakes published in this period —- probably on our site thanks to Mr Merritt , They had big problems …. we do too, if you mess it up .

Even all brand new parts will get you pulling sometimes even locking , constantly adjusting etc for several thousand miles . It is critical that new pieces that are put into turned drums have the shoes ground to match that new size . Drum grinding is not that hard to find , but shoe grinding almost impossible now and finding someone who knows how to do it right is even harder . It was standard stuff in 1960 . It takes real skill and correct machine

Many were scrapped due to “ asbestos dust” that they made . Brutal stiff , no one knew .

This issue happens because of the dual self energizing shoes in front . If a wrong fit in one direction you get almost no braking effort , other way grabbing . Both ways very unhappy for you . It is not “ bad brake design” leading to wholesale changes , it is incompetent work on them . And not incompetent “ on purpose” , .. It is through not knowing how/ why . .

After , what , 25 cars , lesson here is leave it alone even if shoe half worn or scratched drum . You are ahead of game and not like you are driving the car 100 k more miles ..I do not think even deep circumferential grooves hurt anything , despite the visual reaction to that . But wet side must be kept AA++

Related , it will often grab after winter storage , this really threw me down a rathole in the early days , leading to needless painful brake jobs . The reason is rust on drum face makes it randomly self energize way way more . = lock up in your driveway ( typically on one side(!) The cure ?—- apply brakes backing up quickly 4-5 times , fixed .

I think bendix brakes on other cars will self center don’t do this as much . Of course all this applies to 62 back , but still makes sense to me on any old car . I Just rebuilt a 37 small packard ( beautiful brakes , would you believe same 12” as our cars on a car half the weight — and brake lines twice as large ?) all new on the wet side but used the drums and shoes as is . .

Not telling anyone what to do , just info .

Don’t make it worse . And drums are getting really rare too , and trying to change them on the old hubs ( Kanter drums) has been a disaster for me . It gets eccentric, or tilted to axle axis ( try to measure ID with that going on) even with competent machinist help ,= you end up turning your new drum slightly afterwards — to fix that eccentricity, impacts balance etc — ? Ever notice all the balance weights welded on some stock ? and trying to get it centered on a modern lathe takes a really large live center lathe as you need to come from behind to cut it right — and the taper on the rear hubs drives a machinist crazy to get perfect .. you only get a thin line of contact on the mouth of the taper ends .

I spent 3-4 months on and off in early 23 on doing the above ,(yet once again)with engineer hat on — “ Im going to fix this” ,, why this e-mail . The car now has used unturned drums back on it. Working fine . No more pulsation .

Yes, a brake lathe with tooling supposedly fixes all that but they often do not have the cones for holding 60 year old mopar tapered hubs , especially small outer end of taper ( euro VW one fits but a different size smaller main arbor .. of course!) — So they cobble stuff up , (being an expert) , you end up with drums turned beautifully but off center or tilted in casting . “ Sorry , I tried”

Once you turn them to max they are gone in terms of future . another aspect

Brings up using new shoes hopefully turned to size in used scratched drums . I think ok if shoes are truly gone, No choice ..

And thin drums will warp or get out of round much easier than full thickness .

Say you are lacking all this stuff to do it right—- it will settle down in 2 k miles ,which may take years and adjusting for rapid wear every 300 -500 miles ,,and aggravating pulling , noise , pedal drop and general unhappiness . Why the shoe adjuster nut is so often stripped ( see site for a cure for that too )

just sayin …
John

PS if you have a way old brake shop equipped with shoe turning and a way old timer , ? go for it . , But not on rumor of “ I know a great guy” type stuff . Been there . Even then , why ? Someone will say l know shop etc etc ., which is great info . But was it needed is worth asking .

PPS keep old shoes and their matched drums together … may make your day — one day in future , 4 hours instead of forty .

Sent from my iPhone

On Aug 24, 2023, at 1:13 AM, Keith Boonstra <kboonstra.zeegroup@xxxxxxxxx> wrote:

My recollection is that 12.00” is the original maximum ID specified by Chrysler to stay within their specs.

Keith Boonstra

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On Wed, Aug 23, 2023 at 6:48 PM Henry A. Mitchell III <hamlll@xxxxxxxxxxxxxx> wrote:
Does anyone know the maximum ID of the 1957 12 inch brake drum? I found a guy who will turn my drums for me.

Henry Mitchell
300C

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