57 Power Brakes still poor

[avgwarhawk]

18 hours ago, Smartin said:

I pulled the left rear drum off today, and the shoe is not even close to the right arc.

 

After some research, I wasn't interested in spending $400 plus shipping on a new set of 4 drums.  I found a local place about 40 minutes away that will re-arc shoes to drums.  He basically replaces the shoes with a size that is thicker and matches the circumference of the newly turned drums. 

 

It will be about 2 weeks I think before I can confirm if this fixes things.

 

All things being equal...in these braking systems there is no proportion valve like today's vehicles. The front disc in today's vehicles will handle a higher percentage of the brake fluid pressure as all the weight is thrown forward under braking driving the front tires into the ground.  Rear end lifts reducing tire contact and braking ability for the rear tires.    Logically the front brakes should do a majority of the braking. But this is not so without a proportion valve.  All wheel cylinders are receiving the same pressure from the brake fluid.    If the rear shoes are badly arched as described, in theory, you had half or bit more braking ability of the entire brake system.     Let us know how it works out. 

 

Fun 10 minute Army explanation of the hydraulic drum brake system.  Fun to watch even if one knows how it works! 

 

https://commons.wikimedia.org/w/index.php?title=File%3AUS_Army_Training_Film-Hydraulic_Brakes.ogv

 

 

Edited February 18, 2020 by avgwarhawk (see edit history)

[NTX5467]

I would suspect the  "3915F" would be part of the side code, relating to the manufacturer, the lining composition, and possibly the "batch".  But not the cold/hot friction ratings.

 

Many of the name brand brake shoes were manufacturer "oversized" so they would better fit a used brake drum's diameter, I suspect.  No need to arc them for them to work well, by observation.  An older auto supply had a "drum grinder" that would machine the drum's inner surface, but if this was not done correctly (i.e., smooth enough), it would cause problems with early fade until the linings/drums were fully bedded-in.  As a result, many people just replaced the brake shoes, kitted the wheel cylinders, cleaned and lubed the shoe contact points on the backing plates, and called it "good" (which it usually was).

 

A key thing was that with the brake shoe replacements, the general notion was to brake easier until there were some "miles" on the new shoes.  Panic stops were avoided, unless completely necessary.  That allowed the frictions and the brake drum surfaces to "make friends" with each other, so to speak.  When this happened, the pedal was a bit firmer and more solid.  I suspect that arcing the shoes would shorten that period a bit?

 

The other part of this break-in period was to allow the various resins/binders in the friction material to "cook-out" somewhat.  Somewhere, it was mentioned that it was these "gasses" which would interfere with good braking and cause early fade.  Drum or disc brakes.  Which is allegedly one reason the HP disc rotors started coming with slots and holes in them, for quicker dissipation of these gasses.

 

Seems like there used to be a prescribed break-in procedure for new drum brake linings.  How many stops from what mph, for example.  About three segments, speed-wise?  Cooing time between the segments, too.  But that was years ago I saw that!

 

Thanks for posting that information, Old-Tank!

 

NTX5467

[avgwarhawk]

When I performed brake pad/shoe replacement when working at Goodyear a test drive was completed with heavy foot to set in the pads/shoes.     Generally a mile to 2 miles of stop and go was enough. 

[mackensen]

full manifold vacuum ,but how many inches 

[Smartin]

OK Buick people:

 

Rear shoes were arced to their respective drums.  All new hardware installed at the same time, with organic shoes.  Front shoes were checked to drums and they look really good.

 

I did a preliminary adjustment in the air before I put the car down.  When I hit the brake pedal for the first time, it went to the floor.  It hardly stopped the car when I put it in reverse.  I drove it around the neighborhood very gingerly and brought it back to the house to readjust all 4 corners.  After I did that, the brakes responded better.

 

Once I thought I could stop the car in a panic if needed, I proceeded to the back roads to beat on the brakes and try to bed them to the drums.  I put about 10 miles on it, and with every mile, it felt better and better.  I came home and did one more adjustment, and yet another round of heavy braking on the road.  It was finally feeling like an acceptable barking system.  Once I crossed that off the list, the new owner came over and took delivery of the car.

 

Thanks everyone for helping me through this.  It's something I've never had to deal with before.  Now I know virtually every possible problem situation with these older drum brake cars.

[avgwarhawk]

Glad it is sorted. 

[Smartin]

Another followup.  The new owner and I have been working together to get the braking system up to par.  It had gotten better, but still had quite a bit of pedal travel before the brakes wanted to respond.  Since I have driven several of these cars with good brakes, I know this is not right.  As the guy who sold the car, I felt like it was my duty to try everything I could to get it sorted.

 

Today, he came over and we adjusted the anchor pins.  We now have excellent pedal feel with minimal travel when applied.  Why I never did this to begin with, I don't know.  I suppose I didn't know it was that important.  Oops.  Learn something new every day, right?

 

One of his complaints about the brakes today was that when they were on the way over, the car was pulling to the left when brakes were applied.  No amount of adjusting would fix it.  I pulled the hub/drum on the right front.  There was some minor grease contamination on the outer edges of the shoes.  We cleaned it up as best we could since they weren't heavily caked.  Still pulls to the left, but not nearly as bad.  He is going to drive it some more and report back to see if we just need to get a new set of shoes and a new grease seal.

 

Brakes suck.

[lancemb]

2 hours ago, Smartin said:

 

Today, he came over and we adjusted the anchor pins.  We now have excellent pedal feel with minimal travel when applied.  Why I never did this to begin with, I don't know.  I suppose I didn't know it was that important. 

This is unusual; they normally don't need any servicing.  I'm curious what you did; did you move them outward more?

[Smartin]

The anchor pins "center" the shoes in the drums.  The shoe adjusters are to be adjusted out until you can just barely spin the tire.  Then loosen the anchor pin nut on the backing plate.  Make sure it is loose enough that it will move if it is out of center.  This allows it to kind of self-center where it wants to be.  Tighten it back up.  Then loosen the adjuster to where you normally adjust the brakes.

 

The right front one was really far out of whack...most of the others were in decent spots, and didn't seem to move much, if at all.