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Report On My Latest Drum Brake Adventure

Started by Jay Friedman, September 12, 2018, 04:06:10 PM

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Jay Friedman

More than once over the years, my ‘49’s drum brakes have exhibited mysterious symptoms.  I say “mysterious” because in these situations the usual remedies were unable to cure what was wrong, and when the problems were finally solved I had no idea how I did it.

To summarize:

Following a wheel alignment a month or so ago, which followed in turn my having replaced the right front “lever action” shock absorber, my brakes began pulling to the left. 

So, on the supposition that the right front wheel was at fault, I first replaced the five springs holding on the brake shoes as well as the hydraulic hose.  I then cleaned the dust from the backing plate, lightly sanded the lining (which was still thick), wiped down the drum and linings with brake cleaner, lightly greased the points the shoes and springs slide against, bled the hydraulic line and adjusted the star wheel.  The brakes still pulled.  I then tried the "showing the brakes who is boss" approach which has worked for me in the past.  This consists of driving the car at 40-50 mph in a deserted parking lot and then slamming on the brakes (to hopefully seat everything), while holding the steering wheel straight.  No improvement;

2. I did the same as #1 to the left front brake.  The brakes now pulled to the right.  Again, the "showing it who is boss" approach did not work;

3. Deciding to go all out, I then switched the brake shoes on each side to the other side, adjusted them as per the shop manual using a feeler gauge in the adjustment slot on the drum, rebuilt the wheel cylinders on both sides (though neither was leaking) and thoroughly bled both sides.  I also re-torqued the rear spring shackle u-bolt nuts as per a tip I saw in Cadillac literature.  On a road test this morning, the car finally stopped straight.

I don't know what the exact problem or solution was, but thankfully it's solved. 
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

The Tassie Devil(le)

Firstly congratulations on getting it right, but I have to say that doing everything at once, sort of defeats the purpose of doing things one at a time, till it is right, to find out what actually fixed it.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Jay Friedman

Bruce,

At first I tried doing step by step as you said to find the actual fault, but nothing seemed to work and I had been at it for several days.  I'm going to be participating in some car shows soon, so finally did "everything" at once to get it over with.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

Bob Schuman

Jay,
Were there any grooves worn into the machined pads on the backing plates that guide the brake shoes? I have seen them grooved enough to cause brake shoes to stick and not apply or retract smoothly. Incorrect anchor pin adjustment can cause pulling, but you said you adjusted those. My only other thought, based on experience, is that these brakes have a mind of their own and sometimes want to play tricks on us.
Bob Schuman
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

Jay Friedman

Quote from: Bob Schuman on September 13, 2018, 04:32:25 PMWere there any grooves worn into the machined pads on the backing plates that guide the brake shoes? I have seen them grooved enough to cause brake shoes to stick and not apply or retract smoothly. Incorrect anchor pin adjustment can cause pulling, but you said you adjusted those. My only other thought, based on experience, is that these brakes have a mind of their own and sometimes want to play tricks on us.
Bob Schuman

Bob, I agree that drum brakes have a mind of their own, but you may very well have hit upon the cause of my problems.  In fact, the pads right at the top near the anchor pin do have grooves in them on both the right and left backing plates.  I thought that might be all or part of the problem, so coated the grooves with white lithium grease from a tube.  In addition, switching the shoes from one side to the other, may have resulted in the switched shoes no longer lining up with the grooves on each side.  The other pads along the sides and bottom of the shoes do not have any grooves.

I don't know this for a fact, but the shoes currently installed on my car are a set of 8 I bought on the internet several years ago and which I suspect are of foreign manufacture.  Maybe they caused the grooves.  I've decided that next time my car needs a brake job, I'll send my original shoes away to be re-lined.  (The only firm that relines shoes in my area uses a type of lining material meant for large trucks which seems to have less friction.) 

I adjusted the anchor pins several years ago and they have remained in the same position.  As I mentioned in my 1st posting, rather than merely adjusting the star wheel in the usual way, I adjusted the brakes the 2nd time with a feeler gauge through the adjustment slot in the drums to get .015" clearance at each end of the secondary shoes.  This is the adjustment method set forth in the '49 shop manual, and which can't be done unless the anchor pin is correctly adjusted.  (BTW: Art Gardner and I wrote an article on properly adjusting '49 brakes according to the shop manual and the 1949 "Manufacturing Information" manual.  If any readers want a copy let me know.)

All I can say is that drum brakes are mysterious things indeed.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

Jeff Rosansky CLC #28373

Hummmm.
Maybe you should undo everything and then do each step 1 at a time until you find the fault??
Just kidding of course. Good job on that. You probably know more about those brakes now than most.
Thanks for the updates. And yes, I was kidding!!
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Jay Friedman

Jeff, There's nothing like some tongue in cheek comments to keep us anchored in reality.  After all, it's just a hobby and we're supposed  to be having fun when wrestling with some problem with our Cads.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

Roger Zimmermann

When I restored my '56 Biarritz, the backing plates had grooves too. I welded them and reworked them to have a flat surface. I thought that those grooves may affect the braking and it was easy to do that because the parts were removed from the car.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Jay Friedman

Roger,

Good idea.  Maybe I'll have that done next time I do a brake job.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."