Necessity of Bench Bleeding?

[ChrisMinelli]

Hello, I just finished a brake job on my ‘52 Plymouth (new shoes, springs, and cylinders all around) according to the manual.  I flushed the old fluid and bled the cylinders.  I also got a brake adjustment tool from a member here and set the shoes appropriately as much as I could (the cams are a little wonky from age, but I’m within 0.12-0.15 inches of where I need to be). 
 

The car stops smoothly now but the pedal is quite soft.  I bled the air out of all six cylinders.  Is there a necessity to bleed the master cylinder in some way as well?  The manual seemed to indicate the only time you need to do that is when removing or installing the master cylinder.  
 

Do drum brakes make the car stop less effectively than disc brakes?  I’ve always driven rice burners with disc brakes in the past.  Maybe it’s just me. 

[Dodgeb4ya]

Did you make sure each brake shoe lining exactly matched the drum surface 100% ..? 

If the linings don't make 100% drum contact the brakes will be weak till the shoes wear and fit to the drums.

So if you do not get the shoes arced to match each drum you must let them wear in....regardless of your toe/heel adjustment.

So...After 500 miles re adjust them...quick cam adjustment only....drive it

Do last final shoe adjustment again at 1000 miles ...good to go...

They will wear in for a high firm pedal.

These old lockheed double anchor brakes are nothing like modern self adjusting disc brake cars.

Throw a set of pads on it...maybe a set of rear shoes and drive off into the sunset....

Old cars....things take a little more time to cook in the oven.

Patience...it will all be good.

Edited May 9, 2020 by Dodgeb4ya

[TodFitch]

0.12 to 0.15 is really a big clearance for the brake shoes. I assume you mean 0.012 to 0.015.

 

I don’t think you need to bench bleed the master but it sounds like you still have air in the lines. I have much better luck with a pressure bleeder than by the pump the pedal method. Double check for leaks: A pin hole leak at a fitting can make it impossible to get the brakes properly bled.

[DJK]

I bench bled my master after the rebuild before installing. That is the norm for many yrs.

[Sam Buchanan]

8 hours ago, ChrisMinelli said:

Do drum brakes make the car stop less effectively than disc brakes?  I’ve always driven rice burners with disc brakes in the past.  Maybe it’s just me. 

 

As a general rule.....yes....that is why power-assisted disc brakes were revolutionary when they appeared on American cars in the '60's. While there are examples of superb drum brakes (one of my motorcycles had a four-shoe Fontana on the front that could lock the tire at practically any speed) most drum systems will require more pedal pressure and have a different attack/feel than disc brakes. Our old cars have brakes that were optimized for 45-55 mph instead of panic stops from 80 on an interstate highway. That and fade resistance is why disc conversions are installed on old cars for modern highway use.

 

I drive the P15 more conservatively than the 5000 lb F150, realizing I don't have the brake reserve of a modern vehicle. But so far I haven't scared myself and I consider the drums to be adequate if the car is driven as it was designed.

Edited May 9, 2020 by Sam Buchanan

[desoto1939]

21 minutes ago, Sam Buchanan said:

 

As a general rule.....yes....that is why power-assisted disc brakes were revolutionary when they appeared on American cars in the '60's. While there are examples of superb drum brakes (one of my motorcycles had a four-shoe Fontana on the front that could lock the tire at practically any speed) most drum systems will require more pedal pressure and have a different attack/feel than disc brakes. Our old cars have brakes that were optimized for 45-55 mph instead of panic stops from 80 on an interstate highway. That and fade resistance is why disc conversions are installed on old cars for modern highway use.

 

I drive the P15 more conservatively than the 5000 lb F150, realizing I don't have the brake reserve of a modern vehicle. But so far I haven't scared myself and I consider the drums to be adequate if the car is driven as it was designed.

SAM:  Yes the brakes inmy 39 Desoto are ok. But as I stress to other antique car owners that when you get out of your modern car that have power disc brakes and power assit and all of the great new inventions for creature comfort and then you get into your antique car that is 50-80 years old technology you have to think for a minute or two and put your mind into thinking what you are driving and how the car reacts to the driving conditions.

 

You have to be prepared for a stop or situations at all times yes it is a leasurely drive but have to be watching the traffic conditions and traffic signals with more attention.

 

Rich Hartung

desoto1939@aol.com

[busycoupe]

After I rebuilt my brakes with  new shoes and cylinders I found that the pedal was spongy in spite of my having bled all 4 wheels.  I re-bled the system and the pedal was much better.  I think it takes a little while to work all of the air out of the system, especially the upper cylinders on the front.

[Plymouthy Adams]

34 minutes ago, desoto1939 said:

SAM:  Yes the brakes inmy 39 Desoto are ok. But as I stress to other antique car owners that when you get out of your modern car that have power disc brakes and power assit and all of the great new inventions for creature comfort and then you get into your antique car that is 50-80 years old technology you have to think for a minute or two and put your mind into thinking what you are driving and how the car reacts to the driving conditions.

 

You have to be prepared for a stop or situations at all times yes it is a leasurely drive but have to be watching the traffic conditions and traffic signals with more attention.

 

Rich Hartung

desoto1939@aol.com

 

 

to that degree I agree completely...these brakes are fine when in good shape and folks drive them in the realms of realism.  Overdriving the brakes of any car is dangerous.  When I get in my older cars and well, I try to practice this habit when driving all my cars...I carry forward a bit of my learning from the Advanced Riders Course for motorcycles...yes everyone is out to hit me.  IT is not that bad but driving with that thought helps.  A cycle rider even if he is not conscious of it is making more observations and risk calculations as he rides than even the most alert car driver.  I also when on the highway changing lanes and crossing intersections LOOK for the motorcycle, look for the small object at all times chances are you going to see that little foreign car very well.  Accidents do happen, many can be avoided...some are situational where you have no control from your seat behind the wheel...I like the disc brakes and when next my 54 give me brake trouble, I have a set to go on it...but for now and the few trips it makes out of the garage...I just drive it carefully.  The maintenance once installed correctly is minimal for years to come.  Easy to replace and well, other than maybe a tractor in the field nothing else is running shoes on the front at least for decades.

[Sniper]

Modern self energizing drum brakes, our vehicles do not have those, actually take less foot effort to stop than discs.  Discs have better fade resistance, which is the reason they replaced drums.  They don't stop better, anything that overcomes the tire's grip on the road is more than adequate for braking and if you can't lock your brakes you have a problem.

 

Tire technology has substantially improved since our cars were new and that is the major difference you feel, not that you have discs.

[Eneto-55]

27 minutes ago, Sniper said:

Modern self energizing drum brakes, our vehicles do not have those, actually take less foot effort to stop than discs.  Discs have better fade resistance, which is the reason they replaced drums.  They don't stop better, anything that overcomes the tire's grip on the road is more than adequate for braking and if you can't lock your brakes you have a problem.

 

Tire technology has substantially improved since our cars were new and that is the major difference you feel, not that you have discs.

To be completely honest, I don't think I have ever heard that term before - "self-energizing".  So after a bit of looking on-line, I think that our stock brakes are "self-energizing" on the front, right?  As I see the term defined, it means that the rotation of the drum against the brake shoe (lining) produces a sort of locking force, which multiplies the force put upon the shoe from the hydraulic cylinder, giving you the benefit of less actual force necessary at the brake pedal, with greater braking power.  I've always wondered why they used two wheel cylinders on the front, and only one on the rear.  If I understand this principle correctly, then this is the reason - the explanation.

[TodFitch]

14 minutes ago, Eneto-55 said:

To be completely honest, I don't think I have ever heard that term before - "self-energizing".  So after a bit of looking on-line, I think that our stock brakes are "self-energizing" on the front, right?  As I see the term defined, it means that the rotation of the drum against the brake shoe (lining) produces a sort of locking force, which multiplies the force put upon the shoe from the hydraulic cylinder, giving you the benefit of less actual force necessary at the brake pedal, with greater braking power.  I've always wondered why they used two wheel cylinders on the front, and only one on the rear.  If I understand this principle correctly, then this is the reason - the explanation.

 

The Bendix drum brake system was designed so that both shoes were "self-engergized" and for years Chrysler engineers complained that it made the brakes grabby and stuck with the Lockheed system. They claimed that the Lockheed system provided a smoother, more controlled application of the brakes.

 

Don't know what happened, maybe a particularly vocal old time engineer finally retired, but in the early 1960s Chrysler went to the Bendix system they had decried for decades. Pretty sure the '63 Plymouth we had when I was growing up had the Bendix setup and I've heard that was the first year for it.

[Plymouthy Adams]

I am removing a Lockheed dual cylinder fronts from a car I am working now and have gone with twin opposing piston calipers setup disc brakes.  While adequate in stock form...I am no longer stock except in exterior cosmetics.  I have a 32% increase in HP, 36 percent decrease in RPM with OD and rear gear changes. the 55 speed limit these were designed around was left behind many years ago.  This car is a few years beyond 5 decades since production and was 2 decades past time to improve when new.   Never been a fan of these old setups with fixed position shoes....now if these were floating self centering...they do great...except in reverse as speed is increased....then they a joke....

[Plymouthy Adams]

I really do not see  many if any of these old cars doing some serious handling as this.....for you enjoyment I post this..have been to a number of gymkhana and they are fun to watch...I did see a 74 Plymouth cop cruiser in stock format best all the mustangs and corvettes...those guy left with serious egg on their faces that day.

 

the link is quite large....but the car  is small....if nothing else....fast forward to the last few seconds of the little yellow car....serious braking power here folks........

 

 

https://video.search.yahoo.com/search/video;_ylt=AwrExlRB0LZepScAh9KJzbkF?p=mini+at+gymkanna&fr=opensearch&fr2=p%3As%2Cv%3Ai%2Cm%3Apivot&guce_referrer=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&guce_referrer_sig=AQAAADxUKpax1aT6WyXFUA5XeEIf3Vd9CTY6tfBiNQccPGzLfpOitp2OU1Xips-sOcAYhekaTM4T2rScaBRk51-N50YJ3zqczziWQFv98Y-N5TMYzqh5D_J383OMZGefxFohhy94oWfDIYAJvDNZy8GcnEyF1VrQx2pbCAwODoqyOZ-9&_guc_consent_skip=1589039870#action=view&id=1&vid=3a65ed3754c139bf9037690bc813972e

Edited May 9, 2020 by Plymouthy Adams

[Plymouthy Adams]

31 minutes ago, TodFitch said:

 

The Bendix drum brake system was designed so that both shoes were "self-engergized" and for years Chrysler engineers complained that it made the brakes grabby and stuck with the Lockheed system. They claimed that the Lockheed system provided a smoother, more controlled application of the brakes.

 

Don't know what happened, maybe a particularly vocal old time engineer finally retired, but in the early 1960s Chrysler went to the Bendix system they had decried for decades. Pretty sure the '63 Plymouth we had when I was growing up had the Bendix setup and I've heard that was the first year for it.

 

I would say cost measures prevailed and the design change implemented to save money.  The two cylinder set up makes each shoe a leading shoe configuration....where as the rear got a single leading shoe by the single cylinder design and common base point.  

[Ulu]

short linkage   

Edited May 9, 2020 by Ulu

[Sam Buchanan]

1 hour ago, Eneto-55 said:

To be completely honest, I don't think I have ever heard that term before - "self-energizing".  So after a bit of looking on-line, I think that our stock brakes are "self-energizing" on the front, right?  As I see the term defined, it means that the rotation of the drum against the brake shoe (lining) produces a sort of locking force, which multiplies the force put upon the shoe from the hydraulic cylinder, giving you the benefit of less actual force necessary at the brake pedal, with greater braking power.  I've always wondered why they used two wheel cylinders on the front, and only one on the rear.  If I understand this principle correctly, then this is the reason - the explanation.

 

The Fontana drum brake on my Indian-Velo motorcycle was a quad leading-shoe brake.....that thing was a monster! Here is one on a Ducati:

 

 

I, as Plymouthy, suggested revert back to my motorcycle habits when driving the old car....try to confirm the other driver is looking at me as I approach an intersection. But when so many drivers are now gazing at their bellybu....er......phone these days this makes it more of a challange.  ?

 

Edited May 9, 2020 by Sam Buchanan

[Sniper]

Any drum brake set with a fixed pivot point is not self energizing.  Plymouthy  hope you also updated your tires to match the rest of the upgrades.  I have been testing fitting larger tire and rim combos on my 51.  I can fit a P255/50R17 in the back with room for a lot more.  In the front though things are tighter and the backspacing is different by a lot.  Since I wanted to run a "square" setup (all tire sizes the same) P255 is the limit that I can fit in the front with what I consider adequate clearance.  While I could fit larger in the rear anyway since I can't run the same rims I doubt my flattie will ever tax the P255's traction limits.  If I very decide to go with more HP via an engine swap, well I can put bigger tires in if needed. 

 

My son has been helping me sort out the combo and one thing I asked about was a spare tire.  Told him I needed one spare that would fit anywhere and asked him if he had any ideas.  Kid amazes me, he said "the stock tire and rim" which is exactly right. 

[squirebill]

Agreed.  Currently working the brakes on a '49 Suburban.  The front brake lines go from inside the engine compartment up and over the frame then down to the top of the flex hose connection.  This "up and over" the frame loop is a perfect place for air to accumulate in the brake line.

[Plymouthy Adams]

48 minutes ago, Ulu said:

short linkage   

thanks.....I have ridden in a couple of these race prepared early Mini's....they will make a believer out of you..!!  I have a very serious popped up engine like one of these destined for install in my ADO 16 the Mini's slightly larger cousin...the Mini is the ADO15....

[Eneto-55]

OK.  I went back & looked at the description I had seen about this, and I see now where someone DID say that this system would force the entire length of the shoe against the drum surface.  I was thinking of how the leading edge of the brake shoe pushes against the drum surface, which would seem to produce a locking effect.  I have a difficult time "wrapping my head around" some concepts, unless I can see the actual parts in action, so to speak.  I looked again at the diagram in my Service Manual, and it has a picture of the brakes, but doesn't label the photo of the front brake as left or right, except that it DOES label the shoe on the left as REAR, and the one on the right as FRONT.  So this photo is of the right side, and in forward motion the vehicle is moving from left to right, which means that the tire is rotating in a clockwise direction.  This means that the top of the front shoe, and the bottom of the rear shoe are the leading edges of the two brake shoes in relation to the rotating drum.  So the friction between the braking surface and the inside of the drum would actually force the shoe harder against the drum surface, multiplying the force of the pressure at the cylinder, or at the brake pedal.

(Please help me understand this, if I am being dense.)

[Sniper]

Self energizing brakes, maybe this will help you understand why yours are not.

 

 

[MackTheFinger]

1 hour ago, Ulu said:

short linkage   

 

Shriners??

[Plymouthy Adams]

I like the Shriners, they do a lot for kids...they are to have some fun in doing it...but as for these little cars...Shriner toys on steroids.....in their dreams.....my buddy was one of these guys with one of the tiny little clown cars....they not you average go-kart for sure...would like to anyone of ya try that with one of these old Mopars….I for one know their limitations...taking a street corner at anything above idle is one of them....lol

Edited May 9, 2020 by Plymouthy Adams

[Ulu]

I'm not rich enough to be a Shriner. I could only afford the clown car.

 

BTW, my linkage only shows one short video of a Morris doing tailslides and a stoppie.

 

He's put skinny rear tires on and probably only carries 2 gals of gas in back 
(in front?) to get that rear to lay out such a practiced slide. I would like to see the engine....

 

 

Edited May 9, 2020 by Ulu

[ChrisMinelli]

So, do get back to my original post...

 

1.) Try bleeding again after I drive it a bit, and 
 

2.) otherwise, just ignore it and the pedal will firm up with time?