The D**n P15 Brakes

[james curl]

I do not think I would use glass for my brake reservoir as the fluid is flammable and the glass is prone to break. Any type of small can with a screw off lid could be adapted. The Street rod vendors have quite a few different metal reservoirs that bolt to the firewall that you can buy and install.

[K_Jordan]

Robert Horne design on my 48. $20 and works great

[MattWalker]

Well the new master is on and I've put a couple hundred miles on the car.  Fixed some electrical items and I think everything is finally working(except the heat riser)  Planning a trip to Savannah in the p15 soon! I like my p15 again.

 

One thing on the brakes I did notice is that there is alot less feedback when pressing the pedal now.  I don't have to press hard to get the car to stop, not nearly like the old mc...which is cool except I did a worst case scenario on a steep decline go in about 45 and jammed the brakes on and well, the pedal went to the floor and the car thought about stopping and then finally did.  If it was a real emergency I woulda plowed right through.  I hope this is just an adjustment issue on the shoes...  thoughts?

 

Thanks for all the help guys, I love this forum. 

[Don Coatney]

What does your mechanic say?

Edited February 6, 2013 by Don Coatney

[MattWalker]

his theory was the shoes have broken in and need adjustment but only 200 miles on the shoes isn't that much...is it?  I was wondering if the issue is more fundamental, I mean losing the 1/8" of the bore means each stroke pushes less fluid so there is less margin for error in pin size, shoe adjustment and so on, right?  More pressure but at the cost of less movement of fluid to the cylinders?  I mean I suppose I lose pi* 1/16 ^2 * cylinder length? 

[Plymouthy Adams]

what size line did they run to the cylinders...they are designed for 3/16 anything larger can give you issues..soft pedal and not real braking....

[desoto1939]

If the MC cyclinder has been over bored then I would suggest that you replace the MC or have it reseleved with the correct diameter.  This situation sounds very scarry and I would not like to have a low pedal.

 

Also have the mechanic check the brake lining adjustments.  Do another minor adjustment with teh top anchors. This might also be the problem in which the shoes have worn and the  shoe needs to travel more to make contact with the drum.  If you have to much distance then you also have a soft pedal and a lot of people think it is air still inthe lines.

 

Check out the entire brakes system because you only have a single line brake system and these old cars do not stop like your modern car with power brakes.  Also refer to the Tech Section on Brake Adjustmentw with the Ammco and the Miller Brake gage. There is some good information.

 

Rich HArtung

Desoto1939@aol.com

[Plymouthy Adams]

another thing..if they did not use the proper tool to adjust the shoe concentric to the brake drum..your short lived pedal of 200 miles could be just a indication of improper adjust procedure and now only the corners of the shoes have worn away and now you have excessive gap of shoe to drum..this is why it is critical to have the right tool...anything less is a guessing game and will lead to improper shoe wear even if you have a satisfactory pedal but odds are..you will have frequent minor adjustments to maintain a high pedal

[TodFitch]

what size line did they run to the cylinders...they are designed for 3/16 anything larger can give you issues..soft pedal and not real braking....

 

How does that work? If the brake lines and hoses are not changing size when the pressure changes then their diameter should have net effect system volume and thus no effect on pedal travel. I can see where too small a diameter can be an issue as it will restrict flow between the master and slave cylinders. But I am having a hard time undertanding how the diameter could be too large.

[Plymouthy Adams]

Tod you questioned this last time and I posted the answer...I know you think it is odd but I assure you it makes a difference...you can search this answer online and find it true...I invited you to my home to put the 1/4 inch lines back on and see the proof...I do have the lines yet if you wish to schedule an appointment and I will cleqarn my lift for the demosnstation..do a search and you will find that the entire system is desgined for the smaller line and is stated as such by the manufactuer....and by design any change will cause you to suffer a soft pedal..

[MattWalker]

So we are all on the same page this is a 2 chamber 1" mc with a firewall mounted reservoir.  3/16" lines all around.  New shoes, new drums(front nos and rear repro)

 

I adjusted the brakes by hand and when the mechanic did the mc he did as well. Maybe I just need to get ahold of one of those tools and do it right. 

[Dodgeb4ya]

Did you get the shoes arched to fit the drums correctly? If the shoes dont fit you must.....!

Bob

[Don Coatney]

So we are all on the same page

That is why it is  best to keep everything on the same thread. Best to not start a new thread everytime you change the air in your tires.

[MattWalker]

Problem solved...bought an ammco 1750, worth its weight in gold.  I only adjusted the two front wheels so far and the Plymouth stops on a dime now.  I did the worst case scenario test and slammed them on coming down a big hill and I almost ate the steering wheel. 

[Dodgeb4ya]

If you arc the shoes and leave the anchors at factory settings the tool really isn't needed. The shoes seat and fit nicely. But glad you got them working properly!

[55 Fargo]

If you arc the shoes and leave the anchors at factory settings the tool really isn't needed. The shoes seat and fit nicely. But glad you got them working properly!

Bob, I let my shoes wear in a few years, and had the anchors at factory setting, then adjusted minor adjusters to slight drag, brakes were great after that.

By allowing the shoes to wear a bit, is that a similar effect to arcing? I have even wear on these shoes too.......

[Dodgeb4ya]

I did it like you did for years Fred when I drove my 1951 and 53 Plymouths. I didn't have the Miller or the 1750 tools. I do now. I have done so many of these brake jobs over the years that I found out the quickest way to gettin er done and properly fitted for a customer is of course to arc the shoes and leave the anchors at stock settings. I generally pre-check the shoes with the 1750 and usually they are right on.

I used to just slap a set of shoes on my 51 Cranbrook and my 53 Savoy wagon when needed with the anchors at stock. Do the minor adjustment with slight drag. Drive the brakes easy for a week or too. Do another minor adjustment and the pedal was high, safe and firm! The shoe linings wore evenly. Back in the day some of the  shops did not have the tool and had the customers to come back for the second adjustment in a couple weeks to bring the pedal high and firm. That was the way back then.

I learned all this in 1968 from a old asbestos covered brake shop guy that seemed kinda mad when I came in explaining that I could not get the Cranbrook to stop well and the pedal was low. He even gave me a 1955 "MoToRs" shop book which I still have today! He evidently had others like me bugging him about these Lockheed brakes.

The Ammco 1750 or Miller tool set works well and lets you see where you need to move the shoes to fit the drum. If the drum is .030"-.060" the "tool" still won't get you close enough and you will have to arc them or wear them in and keep adjusting the shoes up with the minor adj. cam to achieve the high firm pedal.

Some guys bevel the top and bottom edges of the linings to help them seat in quicker and prevent noise.

I say do it which ever way works for you!

Bob