For What Its Worth

Drum brake R&R

I redid my rear drum brakes.  They would grab at times.  Previous owner had them checked and they didn't find the problem.   It looks like drum brake knowledge has deteriorated.  I found many problems. Some info on redoing drum brakes from my ancient experiences.

Watch out for the brake dust.  It can be nasty stuff.  I would wear a paper mask at least.  If you vacuum the stuff up, be careful, since the filters are not usually fine enough to catch the dust.  I recommend sweeping it up slowly. There is always some dust on the drum and backing plate.

Backing plate.  Make sure it is not bent.  There should be three pads on the front and rear where the brake shoes ride.  They may have little dimples in them.  These should be clean and a VERY LIGHT coat of white grease (Rated for brakes) should be used on them.   You may have to wire brush or lightly file them to get rust off.   Same thing for the area between the stud and brake cylinders on top where the ends of the shoes ride. (See yellow box below)  If you clean and paint the backing plate, be careful with the pads.  They are sliding surfaces.

 

Make sure the pins coming out of the brake cylinders fit into the brake shoes well, but not tight.  Make sure they are clean and smooth in the slots and ends.  Red box in Picture above.

Make sure the brake material on the brake shoes DOES NOT overlap the brake shoes on the side.  If it does, replace or return the shoes.  The metal edge is supposed to slide on the 3 pads not brake material.


Don't take chances with old cylinders.  Rebuild or replace them.  Make sure the new cylinders are the correct ID size.  Be sure Left and right sides match in ID size!  If they don't match one side will brake harder than the other.

DO NOT use cheap brake shoes. Use good name brand shoes. The difference between the cheap brand and good Wagner shoes was $8 for 2 axles on my purchase this week.   

When putting on new shoes, make sure the adjuster is all the way in to begin with. Test fit the drums and adjust out as needed.  Adjusters are directional, they are designed for left and right sides.  When the adjuster arm pushes down on the star it should be opening the distance between shoes.  Reverse them and you have anti-adjusters.  
 

One shoe will have more brake material than the other.  The one with more goes to the REAR.  It is the one that stops against the stud when going forward and takes most of the wear.


If the springs or adjusters are rusty, replace them.  It may take 2 kits.  A brake spring kit, usually covers 2 axles, but you need to know front or back since the keeper pins are usually different lengths front/back. Front brakes are usually wider.  About $10 for a kit.   Also Automatic Adjuster kit, one for each side.  $8-10 each.  A little white lube on the pivot of the adjuster.  ONLY A LITTLE BIT. 

Take care of the spring on the bar that fits between the shoes.  This is for the emergency brake and this spring is not usually in the kits.  The short one in this picture.

If you can't replace the springs, adjusters etc. from memory, only do 1 wheel at a time.  Use the other for reference.  Front to rear is similar.

Turn the drums.  ($6 each) If you have a good brake shop, they should be able to "arc grind" the shoes to match the drums after they are turned.  This eliminates the wear in period over the first few hundred miles.  Warning, "arc grinding" of the shoes may be a dead art.

By turning the adjuster, adjust the shoes to fit the drum to specs.  NOT TOO TIGHT.  The drum should go on and turn, but not have a lot of slop between the brakes shoes and the drum. 

Make sure the drum does not drag on the backing plate.

Final adjustment with Automatic Adjusters.  When the wheels are on, go backwards and use the brakes. Forward then back and brake etc.  A few times.  If you backup slowly or use the brakes lightly or not at all while backing up, you may not be keeping your drum brakes adjusted as they wear.

What was the difference in my rear brakes?  It went from using 3/4 of the distance on the emergency brake to 3 clicks.

This was on my 66.  The springs, adjusters, shoes and cylinders were listed for a 72, the oldest the local parts houses books went.  Same thing.  The Brake flex lines were NOT the same.

Happy Motoring, VHubbard.  May 2009 Last Update Nov 23, 2009

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